JP2003170862A - Body front part structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a body front part structure capable of increasing an impact energy absorption efficiency by surely collapsably deforming the front end portion of a side member even against an impact load input from a diagonal forward direction as well as a frontal direction. <P>SOLUTION: A side member forward area 11F positioned forward of a reinforcement portion 11R is formed aslant to a lateral outside toward the forward direction of a body, and the side member forward area 11F is set by a strength control means 50 to such a strength that the maximum stresses occurring at the front and rear parts of a virtual cross section longitudinally arranged continuously with each other are nearly equal to or larger in the front part than in the rear part. Accordingly, a collapsable deformation is induced from the front end of the side member forward area 11F as the input point of the impact load toward the rear against any impact in the frontal direction or diagonal forward direction. This collapsable deformation can be continuously propagated to the rear and, when the side member forward area 11F interferes with the rear face of a bumper reinforce 12 in the latter half portion of the collapsable deformation, an increase in reaction is suppressed by a reaction control means 60, and an efficient energy absorption can be performed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle body front structure.

[0002]

2. Description of the Related Art As a countermeasure against a vehicle collision, the side members at the front of the vehicle body are axially crushed to absorb the collision energy. For example, Japanese Patent Laid-Open No. 2001-158.
Japanese Laid-Open Patent Publication No. 377 discloses the front structure of the vehicle body.

In this vehicle body front structure, a bead is arranged on the wall portion of the side member front portion having a polygonal cross section to promote axial crushing when an axial input is applied to the side member, thereby colliding energy. Is designed to absorb.

[0004]

However, in such a conventional vehicle body front structure, it is possible to favorably absorb energy against a collision load applied to the side member in the axial direction, but the energy is applied obliquely from the front. With respect to a collision load, there is a tendency that the front portion of the side member is in a deformation mode in which it bends from its root portion.

Therefore, the collision energy at the time of an oblique collision is only temporarily absorbed by the bending of the front portion of the side member, and it becomes difficult to obtain the load characteristic of continuously absorbing the collision load by axial crushing.

Therefore, in order to obtain sufficient collision energy absorption characteristics only by bending the front portion of the side member,
Since it is necessary to significantly increase the rigidity of the side members,
Inevitably, there is a concern that the thickness of the side member will become thicker and the weight of the vehicle body will increase significantly.

Therefore, according to the present invention, the front end portion of the side member can be securely crushed and deformed even when the collision load is input from the front as well as the diagonal front, and the collision energy absorption efficiency can be improved. A front structure is provided.

[0008]

According to the invention of claim 1, reinforcing members for mounting vehicle unit parts are provided on side members arranged in the vehicle front-rear direction on both left and right sides of the front compartment. In a vehicle body front part structure in which a bumper reinforcement extending across the front end of a side member in the vehicle width direction is coupled, a side member front region that is forward from the reinforcing portion of the side member is directed toward the vehicle body front in the vehicle width direction. The maximum stress generated at the front and rear of the virtual cross section that is continuous in the longitudinal direction in the front side region that is formed by inclining outward and is open to the outside is such that the front is greater than or equal to the rear, or close to this. The strength adjustment means for adjusting the strength of the bumper reinforcement is provided, and the front side of the bumper reinforcement is connected to the inner side portion of the vehicle width direction with respect to the connection portion with the side member. The input of the collision load, when the side members are to interfere with the bumper reinforcement deforms sequentially crushed from the front, is characterized in that a reaction force adjusting means for suppressing a reaction force increase of the side member.

According to a second aspect of the present invention, in the vehicle body front structure according to the first aspect, the reaction force adjusting means includes a bumper reinforcement having a cross-sectional height and a side member near a connecting portion of the side member. It is formed as a height-increased portion that is substantially equal to or greater than the cross-sectional height of the member, and is formed as a height-reduced portion that is smaller than the cross-sectional height of the side member in the portion that is located inside the vehicle by a predetermined distance from the connecting portion of the side member. It is characterized in that the height-reduced portion is made to correspond to the central portion of the side surface avoiding the ridgeline of the side member.

According to a third aspect of the present invention, in the vehicle body front structure according to the first aspect, the reaction force adjusting means sets the bumper reinforcement so that its sectional height is substantially equal to or greater than the sectional height of the side member. A bump having a width smaller than the cross-sectional height of the side member is formed on the rear surface of the bumper reinforcement that is located inside the vehicle by a predetermined distance from the connecting portion of the side member. It is characterized in that it is arranged corresponding to the central part of the side surface that avoids.

[0011]

According to the first aspect of the invention, the front region of the side member, which is the front side from the reinforcing portion, is formed to be inclined outward in the vehicle width direction toward the front of the vehicle body. The region, the strength adjusting means, the maximum stress generated in the front portion and the rear portion of the virtual cross section continuous in the longitudinal direction of the side member front region, since the front portion is set to the rear portion or more, or to a strength close to this, Whether a collision load is input to the front end of the side member from the front direction or diagonally forward, crush deformation is induced from the front end of the front region of the side member, which is the input point of the collision load, toward the rear, and the crush deformation is caused. The efficiency of absorbing collision energy can be increased by continuously propagating to the rear portion of the front region of the side member.

At this time, the front region of the side member is crushed and deformed including the ridgeline of the closed cross section, and as the crushed deformation progresses, it interferes sequentially with the rear surface of the bumper reinforcement, but the reaction force is adjusted to the bumper reinforcement. Since the means is provided, the reaction force adjusting means can suppress an increase in the reaction force of the side member, so that the deformation of the side member can be promoted and efficient energy absorption can be performed.

According to the invention of claim 2, claim 1
In addition to the effect of the invention described above, the reaction force adjusting means is configured as a height changing portion of a bumper reinforcement having a height increasing portion and a height reducing portion, and the height reducing portion is provided with a ridge line of a side member. Since it is made to correspond to the center of the side face avoiding, the deformation mode of the front region of the side member due to the collision load input from the front is initially a closed cross section because the front region of the side member interferes with the height increasing portion. The entire cross section including the highly rigid ridge line of the side member is crushed and deformed. As the crush deformation progresses, the side member interferes with the height-reduced portion, and the side member front region has a low rigidity side surface. The deformation is started from, and it is possible to easily perform the deformation while suppressing the increase of the reaction force.

According to the invention of claim 3, claim 1
In addition to the effect of the invention described above, the reaction force adjusting means is provided with a protrusion having a width smaller than the sectional height of the side member at a required portion of the rear surface of the bumper reinforcement in which the sectional height is formed to be substantially equal to or more than that of the side member. Since the projections are arranged so as to correspond to the center of the side surface avoiding the ridgeline of the side member, the deformation mode in the front region of the side member due to the collision load input from the front is initially the side member. The front area interferes with the bumper reinforcement with an increased cross-section height, causing the entire cross-section including the highly rigid ridgeline of the side member with a closed cross-section to be crushed and deformed. The member interferes with the protrusion, and the front side region of the side member starts to be deformed from the side surface having low rigidity, so that the deformation can be easily performed while suppressing the increase of the reaction force. That.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIGS. 1 to 11 show a first embodiment of a vehicle body front portion structure of the present invention. FIG. 1 is an external perspective view of an automobile targeted by the present invention, and FIG. 3 is a schematic plan explanatory view showing the skeleton structure on the right side of the portion, FIG. 3 is a perspective view of the front region of the side member, FIG. 4 is an enlarged cross-sectional view taken along the line AA in FIG. 3, and FIG. FIG. 6 is an explanatory view showing a morphological model (a) and a stress distribution diagram (b), FIG. 6 is a stress distribution diagram showing the concept of the strength adjusting means, and FIG. 7 is a deformation mode of the side member front region by the reaction force adjusting means (a). 8A to 8C are explanatory views showing the steps in sequence, FIG. 8 is an explanatory view showing a bumper reinforcement forming method, and FIG. 9 is an end perspective view of another bumper reinforcement forming method. Explanatory drawing shown by the cross section (b) and the CC cross section (c), FIG.
0 is an explanatory view showing a structure (a) in which the reaction force adjusting means of the bumper reinforcement is not provided and a structure (b) in which it is provided, and FIG. 11 compares the reaction forces of the side members with and without the reaction force adjusting means. It is a graph.

The vehicle body front structure of this embodiment is applied to the front compartments F and C of the vehicle body 10 shown in FIG.
As shown in FIG. 2, the skeleton structure includes side members 11 arranged in the vehicle front-rear direction on both left and right sides, and general parts of these side members 11 are arranged in parallel and each side member 11 A bumper reinforcement 12 forming a skeleton of a bumper (not shown) is connected across the front end of the.

Further, behind the respective side members 11, extension side members 13 extending from the dash panel 17 to the lower surface side of the floor panel 18 are continuously provided, and each extension side member 13 is provided.
A side sill 14 is arranged substantially parallel to the outer side in the vehicle width direction, and the front end portions of the extension side member 13 and the side sill 14 are joined by an outrigger 15.

A dash cross member 16 is connected so as to straddle the continuous portions of the side members 11 and extension side members 13.

A front wheel 2 is provided on the rear side of the side member 11.
A suspension arm 21 for supporting 0 is attached directly or via a suspension member (not shown), and a power unit 30 such as an engine as a vehicle unit component is mounted via a mount bracket 31 between the left and right side members 11. To be done.

As shown in FIG. 3, the side member 11 is provided with a reinforcing portion 11R (shown as a satin portion in FIG. 3) in which the wall thickness of the side member 11 is increased, at a mounting portion of the mount bracket 31.

That is, as shown in FIG. 3, the side member 11 is closed by fixing both side flange portions of the second plate 11b having a U-shaped cross section to the flat plate-shaped first plate 11a by spot welding or the like. It is formed as a cross-sectional structure, and the reinforcing portion 11R is formed by joining and disposing a reinforcing plate on the inner peripheral surface.

Here, in the present embodiment, as shown in FIG. 3, the side member front region 11F, which is the front side from the reinforcing portion 11R of the side member 11, faces toward the front side of the vehicle body (front side in FIG. 3). It is formed so as to be inclined outward at the vehicle width direction (left side in FIG. 3) by a predetermined angle θ.

Then, in the front side region 11F of the side member which is opened outward, the maximum stress generated in the front and rear portions of the imaginary cross sections Ia, Ib ... Ie continuous in the longitudinal direction as shown in FIG. The side member plate thickness changing structure 50 is configured as a strength adjusting means such that the part has a strength equal to or more than the rear part (front part ≧ rear part) or close thereto, and the plate thickness distribution of the side member front region 11F is set in the longitudinal direction. Has been changed to.

That is, the side member plate thickness changing structure 50 is
As shown in FIG. 4, the plate thicknesses t1, t2, t3 ... t6 (t1 <t2 <t3 from the front end direction of the side member front region 11F).
<... <t6) A plurality of plate members 51a, 5 that change stepwise
51f is composed of a composite panel material 52 formed by welding the entire circumferences of 1b, 51c ... 51f, and the thickest plate material 5 is formed.
If is the reinforcing portion 11R.

The front area 11F of the side member
When the collision load F from the front statically acts on the front end portion of the side member front region 11F as shown in FIG. 5, each virtual cross section Ia, Ib, ...
e (See Fig. 3) Axial force component stress (FY / A
(Y)) and moment component stress ({FX × (L−y)}
The maximum value of the sum of / Z (y) is the front portion ≈ the rear portion, and the upper limit value is the yield strength σ of the side member constituent material.
(Y).

Σ (y) = {FY / A (y)} + {FX × (L−y)} / Z (y) Equation 1 At this time, the upper limit value of the maximum stress due to the side member plate thickness change structure 50 Is set on the basis of the yield strength of the material forming the side member 11 as described above, and as a result, as shown in FIG. 6, the distribution of the yield strength σ (y) with respect to each plate material 51a, 51b, 51c, ... can get.

By the way, the side member front region 11
Since F is inclined outward in the vehicle width direction as shown in FIG. 3, the collision load F from the front direction is input as shown in FIGS. 11
Is crushed and deformed sequentially from the front, and as the crush deformation progresses, it interferes with the rear surface of the bumper reinforcement 12, but in the present embodiment, the stage where the interference of the side member 11 progresses with the bumper reinforcement 12 by a predetermined amount. A height changing portion 60 is provided as a reaction force adjusting means for suppressing an increase in the reaction force of the side member 11.

The height changing portion 60 increases in height so that the sectional height of the bumper reinforcement 12 becomes substantially equal to or more than the sectional height h0 of the side member 11 in the vicinity of the connecting portion C with the side member 11. Formed as a portion 61 (cross-sectional height h1), and a connecting portion C with the side member 11
Is formed as a height reducing portion 62 (cross-section height h2) smaller than the cross-sectional height h0 of the side member 11 at a portion closer to the inner side (right side in FIG. 3) from the height reduction portion. The portion 62 is defined by the ridge lines 11c, 11
It is configured so as to correspond to the side surface central portion 11e avoiding d.

The height changing portions 60 formed on the bumper reinforcement 12 are formed by press forming using hydraulic pressure as shown in FIG. The height reduced portion 62 is formed by crushing, and the height reduced portion 62 and the height increased portion 61 are connected in series with the step portion 63 as a boundary.

In addition, the height changing portion 60 is shown in FIG.
As shown in (b), the bumper reinforcement 12 is extruded from a light alloy material into a shape in which partition plates 64 are provided on the upper and lower portions of the closed cross section so that the cross section has an eye shape.
The upper and lower surfaces of the portion corresponding to the height reduction portion 62 are shown in FIG.
It can also be formed by cutting by machining as shown in (a) and (c).

Further, the height changing portion 60 is the same as that shown in FIG.
There are various methods other than the hydraulic forming of Fig. 9 and the machining of the light alloy extruded material shown in Fig. 9. For example, a variable cross-section light alloy extruded material formed along the final cross-sectional shape at the time of extrusion molding can be used. it can.

(Operation) According to the vehicle body front structure of the first embodiment having the above-described structure, as shown in FIG. 2, a static collision load F is applied to the front end of the front side member 11 from the front.
When the action is performed, as shown in FIG. 3, the virtual cross sections Ia, Ib ... Which are continuous in the longitudinal direction of the side member front region 11F.
The maximum value of the sum of the axial force component stress (FY / A (y)) and the moment component stress ({FX × (L−y)} / Z (y)) generated in Ie becomes the front portion ≈ the rear portion. Since the upper limit value is the yield strength σ (y) of the side member constituent material, at the time of collision, which is a dynamic phenomenon, the front end portion of the front side member 11 which is the input point reaches the yield area of the material and the plasticity increases. Deformation occurs, and as a result, when the collision load F is input, the side member front region 11F induces a crushing deformation (crushing) from the front end portion which is an input point, and the crushing deformation is continuously rearward. It can be deformed in a mode that propagates to, and can reliably absorb collision energy.

At this time, as described above, since the side member front region 11F is formed so as to be inclined outward in the vehicle width direction toward the front of the vehicle body, not only the collision from the diagonal front but also the front direction. Even in the event of a collision, the side member front region 11F can be continuously crushed and deformed from the tip portion.

Further, the side member front region 11F inclined outward in the vehicle width direction as described above is provided with the side member 1
Since the front end portion of No. 1 can be arranged further outward in the vehicle width direction, the input support range at the vehicle body front end portion can be expanded in the vehicle width direction.

Here, as described above, the side member front region 11F can be continuously crushed and deformed from the front end side to the rear side against a frontal collision, but the strength and rigidity are high in the vicinity of the reinforcing portion 11R. Therefore, the reaction force tends to increase.

However, according to the structure of the present embodiment, the ridge line 1 in which the side member front region 11F has a closed cross section as shown in FIG. 7B from the state of FIG. 7A at the initial stage of collision.
The crush deformation K including 1c and 11d (see FIG. 3) is performed, and as the crush deformation K progresses, the bumper reinforcement 12 is deformed.
The rear surface 12a is sequentially interfered with, and the interference point is crushed and deformed K.
When the vehicle moves rearward as the vehicle moves, the crush deformation K due to the height changing portion 60 of the bumper reinforcement 12 is caused.
It is possible to suppress an increase in the reaction force of the front side member 11 in the latter half of the above.

That is, the height decreasing portion 62 of the height changing portion 60 is formed into the ridge lines 11c and 11 of the front side member 11.
Since it is arranged so as to correspond to the side surface central portion 11e (see FIG. 3) avoiding d, the side surface central portion 11e of the side member front region 11F becomes the height decreasing portion 62 as the crush deformation K progresses. When the interference occurs, as shown in FIG. 7C, the side member front region 11F starts to be deformed from the side surface 11e having low rigidity, suppresses an increase in reaction force, promotes the crush deformation K, and efficiently absorbs energy. Can be done.

FIG. 11 shows a reaction force characteristic P of the side member 11 when the bumper reinforcement 12 having no height changing portion 60 as shown in FIG. 10A is used.
And the reaction force characteristic Q of the side member 11 when the bumper reinforcement 12 of the present embodiment in which the height changing portion 60 is formed as shown in FIG. Side member front region 11 with the progress of
As the interference portion between F and the bumper reinforcement 12 increases, in the reaction force characteristic Q, a large reaction force reduction region can be secured in the latter half portion where the height reduction portion 62 is provided.

Therefore, the crushing deformation K when the front region 11F of the side member interferes with the bumper reinforcement 12 can be positively performed, and the energy of the collision load F by the side member 11 can be efficiently absorbed. .

Further, in the first embodiment, the height changing portion 60 used as the reaction force adjusting means only needs to be processed so as to change the sectional heights h1 and h2 of the bumper reinforcement 12, so that the reaction force can be changed. The overall structure of the adjusting means can be simplified.

By the way, in the present embodiment, the side member plate thickness changing structure 50 includes a plurality of plate members 51a, 51b, 51c ... 51 having plate thicknesses t1, t2, t3, ...
Since f is formed by using the composite panel material 52 joined so that the plate thickness thereof changes stepwise, the virtual cross sections Ia, Ib continuous in the longitudinal direction of the side member front region 11F.
... The maximum stress generated in Ie is approximately controlled, so that the crush deformation K from the front end portion of the side member front region 11F can be induced without any trouble, and the side member front region 11F can be easily formed. be able to.

Further, since the side member plate thickness changing structure 50 has a sectional size changing structure in which the sectional size of the side member front region 11F is changed in the longitudinal direction as described above, the collision load F is influenced by the side member 11. When it is input to the front end of the side member, it becomes easier to control the maximum stress that occurs in the virtual cross section that is continuous in the longitudinal direction of the side member front region, and it becomes easier to adjust the strength balance. The crush deformation K from the front end of 11F can be more reliably induced.

The plate members 51a, 51b, 51c ... 5
The number of 1f is not limited to this embodiment, and the number may be determined according to the required crushing characteristics of the side member front region 11F.

Further, the side member plate thickness changing structure 50 is
Although the maximum stress generated at the front and rear of the imaginary cross section of the side member front region 11F is set to be front ≈ rear, the front is not limited to this, that is, front ≧
The strength may be set to the rear part or a state close to this.

(Second Embodiment) FIGS. 12 to 15 show a second embodiment of the present invention, in which the same components as those in the first embodiment are designated by the same reference numerals, and a duplicate description will be omitted.

FIG. 12 is a schematic plan explanatory view showing a skeleton structure on the right side of the front part of the vehicle body, FIG. 13 is a rear perspective view showing an essential part of the bumper reinforcement, and FIG. 14 is taken along line D-D in FIG. FIG. 15 is an enlarged sectional view, and FIG. 15 is a plan view showing a deformed state of the front region of the side member.

The vehicle body front structure of the second embodiment is shown in FIG.
As shown in FIG. 2 and FIG. 13, the reaction force adjusting means is constituted by a protrusion 70 attached to the rear surface of the bumper reinforcement 12.

In the second embodiment, the sectional height h1 of the bumper reinforcement 12 is previously formed to be substantially equal to or greater than the sectional height h0 of the side member, and the connecting portion C of the side member 11 of the bumper reinforcement 12 is formed. The protrusion 70 having a width h3 smaller than the sectional height h0 of the side member 11 is provided on the rear surface of the side member 11 which is closer to the inside of the vehicle by a predetermined distance from the side member 11, as in the first embodiment. Side center part 11 avoiding ridges 11c and 11d
It is arranged corresponding to e.

The projection 70 is formed as a channel material bent in a U-shaped cross section as shown in FIG. 14, and both end flanges 71 and 71a thereof are attached to the bumper reinforcement 1.
It is joined to the central portion of the rear surface 12a in the height direction by continuous welding or the like. Of course, when the projection 70 interferes with the front side member 11,
It has sufficient rigidity to crush and deform K.

Therefore, also in the second embodiment, as in the first embodiment, as shown in FIG. 15, the front side member is input by the collision load F from the front direction or the collision load F1 from the diagonal front. In the deformation mode of the region 11F, initially, the front region 11F of the side member interferes with the bumper reinforcement 12 having the increased sectional height h1, and the ridgelines 11c, 11 of the front side member 11 having a closed cross section.
The collapse deformation K of the entire cross section including d is caused.

As the crush deformation K progresses, the front side member 11 interferes with the projection 70, and the side surface 11 of the side member front region 11F having a low rigidity.
Deformation is started from e, the increase of the reaction force in the latter half of the crush deformation K can be suppressed, and the deformation can be promoted.
The same effect as that of the embodiment can be obtained.

The reaction force adjusting means forms the sectional height h1 of the bumper reinforcement 12 to be substantially equal to or greater than the sectional height h0 of the front side member 11, and adds a protrusion to the rear surface 12a of the bumper reinforcement 12. Therefore, the structure can be simplified without complicated processing of the bumper reinforcement 12.

Although the vehicle body front structure of the present invention has been described by taking the first and second embodiments as examples, other embodiments having other configurations can be adopted without departing from the scope of the present invention. .

[Brief description of drawings]

FIG. 1 is an external perspective view of an automobile targeted by the present invention.

FIG. 2 is a schematic plan explanatory view showing a skeleton structure on the right side of the front portion of the vehicle body in the first embodiment of the invention.

FIG. 3 is a perspective view of a side member front region according to the first embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view taken along the line AA in FIG.

FIG. 5 is an explanatory view showing the strength adjusting means in the first embodiment of the present invention with an input form model (a) and a stress distribution diagram (b).

FIG. 6 is a stress distribution diagram showing the concept of strength adjusting means in the first embodiment of the present invention.

7A to 7D show deformation modes of a side member front region by the reaction force adjusting means in the first embodiment of the present invention.
Explanatory drawing which shows in order by (c).

FIG. 8 is an explanatory view showing an example of a bumper reinforcement forming method according to the first embodiment of the present invention.

FIG. 9 is an explanatory view showing another forming method of the bumper reinforcement in the first embodiment of the present invention with an end perspective view (a), a BB line cross section (b), and a CC line cross section (c). .

FIG. 10 is an explanatory view showing a structure (a) in which a reaction force adjusting means for bumper reinforcement is not provided and a structure (b) provided in the first embodiment of the present invention in comparison.

FIG. 11 is a graph comparing the reaction forces of the side members with and without the reaction force adjusting means according to the first embodiment of the present invention.

FIG. 12 is a schematic plan explanatory view showing a skeleton structure on the right side of the front portion of the vehicle body in the second embodiment of the invention.

FIG. 13 is a rear perspective view showing a main part of a bumper reinforcement according to a second embodiment of the present invention.

FIG. 14 is an enlarged cross-sectional view taken along the line DD in FIG.

FIG. 15 is a schematic plan explanatory view showing a deformed state of a side member front region in the second embodiment of the present invention.

[Explanation of symbols]

FC front compartment 10 car body 11 side members 11F Side member front area 11R reinforcement part 11c, 11d ridge 11e Side center part 12 Bumper reinforcement 12a rear surface 30 power units (vehicle unit parts) 50 Side member thickness change structure (strength adjusting means) 60 Height change part (reaction force adjusting means) 61 Height increase part 62 Height reduction area K crush deformation Ia, Ib ... Ie virtual cross section

Claims (3)

[Claims] 1. Reinforcing parts for mounting vehicle unit parts are provided on side members arranged in the vehicle front-rear direction on both left and right sides of the front compartment, and extend in the vehicle width direction across the front ends of these side members. In a vehicle body front structure in which a bumper reinforcement is coupled, a side member front region that is forward from the reinforcing portion of the side member is formed by inclining outward in the vehicle width direction toward the front of the vehicle body. In the front region of the side member, the strength adjusting means is provided such that the maximum stress generated in the front and rear portions of the virtual cross section continuous in the longitudinal direction is such that the front portion has a strength equal to or higher than the rear portion, or close to this. By inputting the collision load from the front, the side member is located inside the bumper reinforcement in the vehicle width direction inside the connection with the side member. Vehicle body front structure, characterized in that when the interfering with bumper reinforcement deforms sequentially crushed from the front, provided with a reaction force adjusting means for suppressing a reaction force increase of the side member. 2. The reaction force adjusting means forms the bumper reinforcement as a height-increasing portion whose cross-sectional height is approximately equal to or higher than the cross-sectional height of the side member in the vicinity of the connecting portion of the side member, and at the same time, At a portion closer to the inner side of the vehicle by a predetermined distance from the connecting portion, a height reducing portion smaller than the sectional height of the side member is formed, and the height reducing portion is made to correspond to the central portion of the side surface avoiding the ridgeline of the side member. The vehicle body front structure according to claim 1, which is configured. 3. The reaction force adjusting means forms the bumper reinforcement so that its sectional height is substantially equal to or greater than the sectional height of the side member, and a predetermined distance from the connecting portion of the side member of the bumper reinforcement is inside the vehicle. It is characterized in that a protrusion having a width smaller than the sectional height of the side member is provided on the rear surface of the side member, and the protrusion is arranged corresponding to the center of the side surface avoiding the ridge line of the side member. The vehicle body front structure according to claim 1.