JP2003306095A - Bumper installation structure for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bumper installation structure for a vehicle in which load input to a bumper reinforcement can be absorbed by deformation of a desired car body side member. <P>SOLUTION: The bumper reinforcement 31 extended in a car width direction is installed on a car body 15 as its position in the car width direction is regulated by a positioning bolt 6 and a positioning bolt hole 11 to position it in the car width direction. Around the positioning bolt 6, a pair of a right and a left semicircular slits 22 and 22 are formed. Between an upper and a lower parts facing each other, a pair of an upper and a lower narrow plate bridge parts 23 and 23 are formed. A disc-shaped seat surface 24 where the positioning bolt 6 is erected is connected to an installation seat surface 4d to be deformable by load input in the car width direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle bumper mounting structure capable of positioning in the vehicle width direction.

[0002]

2. Description of the Related Art Conventionally, as a bumper mounting structure for a vehicle,
The ones shown in FIGS. 11 to 14 are known.

In such a vehicle bumper mounting structure, for example, as shown in FIG. 11, the front portion of the vehicle 1 has a substantially mountain-like shape in which a central portion 3a is projected toward the front of the vehicle in a top view. Bumper 3 is provided. This bumper 3 is provided with a bumper fascia 3b that constitutes the front surface side.

Inside the bumper fascia 3b, along with the shape of the bumper 3, the bumper reinforcement 3
c is extended along the vehicle width direction.

At both left and right edges of the vehicle 1, a pair of left and right side members 2 and 2, which are skeleton members on the vehicle body side, extend along the vehicle front-rear direction.

Further, the front end portions 2 of the side members 2 and 2 are
The bumpers 3a, 2a are provided with bumpers 4a, 4b for supporting and mounting the bumper 3.

Among them, the bumper stay 4a is provided with a positioning bolt 6 as a positioning projection and a fixing bolt 7 so as to project toward the front of the vehicle.

A pair of fixing bolts 7, 7 are provided on the bumper stay 4b so as to project toward the front of the vehicle.

On the other hand, in the bumper reinforcement 3c, the positioning bolt 6 is inserted in the vicinity of the right end portion of the rear surface portion 3d facing the bumper stay 4a to regulate the position in the vehicle width direction. 11 and a fixing bolt hole 12 are formed.

Fixing bolt holes 13 and 14 for inserting the fixing bolts 7 and 7 are formed in a portion facing the bumper stay 4b in the vicinity of the other left end portion of the back surface portion 3d of the bumper reinforcement 3c. There is.

Of these, the positioning hole 11 is shown in FIG.
As shown in FIG. 3, the fixing bolt holes 12 to 14 have a long hole shape extending in the vehicle width direction (X direction).

Then, the positioning bolt 6 inserted into the positioning hole 11 and the fixing bolt holes 12 to 14 is inserted.
, And the nut members 10 are respectively screwed into the fixing bolts 7 and so that the bumper reinforcement 3c is fastened to the bumpers 4a and 4b.

Next, the operation of the conventional vehicle bumper mounting structure will be described.

In the conventional vehicle bumper mounting structure thus constructed, the positioning bolts 6 and the fixing bolts 7 are inserted into the fixing bolt holes 12 to 14 and the nut members 10 are screwed respectively. By doing so, the bumper reinforcement 3c becomes the bumper stays 4a, 4b.
Will be concluded.

At this time, the positioning bolt 6 is inserted into the positioning hole 11 having a round hole shape, thereby positioning the bumper reinforcement 3c in the vehicle width direction X.

Further, the dimensional error is caused by the fixing bolts 7 ...
Are absorbed by being loosely fitted in the fixing bolt holes 12 to 14 in the vehicle width direction. Therefore, even if there is a pitch error or the like between the positioning bolt 6 and the fixing bolts 7, ...

[0017]

However, in such a bumper mounting structure, as shown in FIGS. 13 and 14, for example, due to a light collision such that the bumper reinforcement is deformed, the vehicle longitudinal direction Y (X When a load F (in a direction perpendicular to the direction) is input to the substantially mountain-shaped central portion 3b of the bumper reinforcement 3c, a component force Fx in the X direction is applied to the bumper reinforcement 3c.

At this time, since the movement of the bumper reinforcement 3c in the X direction is restricted by the positioning bolt 6 and the positioning bolt hole 11, as shown in FIG. 14, the side member 2 is indicated by the arrow Ax. There is a problem that the side member 2 is deformed toward the outside in the width direction, and a desired axial collapse deformation or the like of the side member 2 along the vehicle front-rear direction cannot be obtained.

It is an object of the present invention to provide a vehicle bumper mounting structure capable of absorbing a load input to a bumper reinforcement by a desired deformation of a member on the vehicle body side.

[0020]

In order to achieve the above object, in the vehicle bumper mounting structure of claim 1, a bumper reinforcement extending along the vehicle width direction performs positioning in the vehicle width direction. In a vehicle bumper mounting structure in which a vehicle width direction positioning portion regulates a vehicle width direction position and is mounted on a vehicle body, the vehicle width direction positioning portion includes a fragile means that is deformable by a load input in the vehicle width direction. It features a vehicle bumper mounting structure.

In the vehicle bumper mounting structure of the present invention thus configured, the bumper reinforcement extending along the vehicle width direction is positioned by the vehicle width direction positioning portion for positioning in the vehicle width direction. It is mounted on the vehicle body with its width position restricted.

Therefore, the bumper reinforcement can be mounted on the vehicle body with good positioning accuracy.

Further, when a load is applied to the bumper reinforcement, the fragile means provided in the vehicle width direction positioning portion is deformed by the load input in the vehicle width direction to release the load in the vehicle width direction.

Therefore, a desired deformation of the vehicle body side member such as axial crush deformation can be generated only by the load applied to the bumper reinforcement in the vehicle front-rear direction, and the load can be absorbed.

In the vehicle bumper mounting structure according to a second aspect of the invention, the vehicle width direction positioning portion projects from a mounting seat surface provided on either the vehicle body side or the bumper reinforcement side. And a bolt hole that is provided on the other side opposite to the bolt member and that regulates the position in the vehicle width direction by inserting the bolt member, and screwing the bolt hole into the bolt member so that the peripheral edge of the bolt hole is the mounting seat surface. The bumper mounting structure for a vehicle according to claim 1, wherein a fastening means having a nut member to be fastened to is provided, and the weakening means is constituted by a slit formed in a peripheral edge of the mounting seat surface or a peripheral edge of the bolt hole. There is.

According to a second aspect of the present invention configured as described above, since the fragile means is constituted by a slit formed on the peripheral edge of the mounting seat surface or the peripheral edge of the bolt hole, the mounting seat surface is formed. When a load in the vehicle width direction is applied to the peripheral edge or the bolt hole peripheral edge, the slit peripheral edge is deformed by the load input in the vehicle width direction, and the load in the vehicle width direction is released.

Further, according to a third aspect of the invention, the fragile means is a shaft portion of a bolt member provided on either the vehicle body side or the bumper reinforcement side in the vehicle width direction positioning portion. The bumper mounting structure for a vehicle according to claim 1 or 2, wherein the bumper mounting structure has a notch formed in the portion.

According to a third aspect of the present invention, the cutout portion is formed in the shaft portion of the bolt member provided on either the vehicle body side or the bumper reinforcement side. Therefore, when a load is applied in the vehicle width direction, the notch portion bends to release the load in the vehicle width direction.

Therefore, it is possible to generate a desired deformation of the member on the vehicle body side, such as a shaft crush deformation, only by the load applied to the bumper reinforcement in the vehicle front-rear direction to absorb the load.

[0030]

1 to 6 show a front bumper mounting structure for an automobile according to a first embodiment to which a vehicle bumper mounting structure of the present invention is applied.

The same or equivalent parts as those in the conventional example will be described with the same reference numerals.

First, in terms of the configuration, in the front bumper mounting structure of the first embodiment, as shown in FIG. 2, the front portion of the vehicle 15 has a central portion 3a facing forward in a top view. A bumper 30 having a substantially mountain shape is provided.

This bumper 30 is located on the inside of the bumper fascia 3b and the bumper fascia 3b constituting the front side, and is extended along the vehicle width direction along the shape of the bumper 30. And a reinforcement 31.

In the first embodiment, as shown in FIG. 3, the central portion 31a of the bumper reinforcement 31 is provided.
And the camber angle θ of the central portion 3a of the bumper fascia 3b.
A camber angle θ2 that is substantially the same as 1 is formed.

Further, side members 2 and 2, which are skeleton members on the vehicle body side, are provided on both left and right edges of the vehicle 15 so as to extend in a pair of left and right along the vehicle front-rear direction.

The front ends 2a, 2a of the side members 2, 2 are provided with a pair of left and right bumpers 4c, 4b for supporting and mounting the bumper 3.

Among them, a positioning bolt 6 as a vehicle width direction positioning portion and a fixing bolt 7 are provided on the mounting seat surface 4d of the bumper stay 4c so as to project toward the front of the vehicle.

Around the mounting seat surface 4d of the positioning bolt 6, semi-circular slits 22, 2 as weakening means.
Two pairs of left and right are formed.

A pair of upper and lower narrow plate-shaped bridge-shaped portions 23, 23 are formed between the upper and lower end portions of the slits 22, 22.

That is, the slits 22 have inner and outer diameters with the central axis of the inserted positioning bolt 6 as the center, and a pair of left and right is formed at left and right symmetrical positions with the positioning bolt 6 sandwiched therebetween. ing. These arc grooves 22, 2
The upper and lower ends of the positioning bolt 6 terminate at substantially vertical positions above and below the positioning bolt 6, and the bridge-shaped portion 2 is provided between the opposing ends.
3, 23 are formed.

By the bridge portions 23, 23,
Disc-shaped seat surface 24 on which the positioning bolt 6 is erected.
Is connected to the mounting seat surface 4d and is supported so as to be deformable by a load input in the vehicle width direction.

The bumper stay 4b on the left side is
A pair of fixing bolts 7, 7 are provided so as to project toward the front of the vehicle.

Further, of the bumper reinforcement 31, the positioning bolt 6 is inserted in the vicinity of one end of the rear surface portion 3d facing the mounting seat surface 4d of the bumper stay 4a to regulate the position in the vehicle width direction. Positioning bolt hole 11
And a fixing bolt hole 12 is formed.

In the vicinity of the other end of the back surface portion 3d of the bumper reinforcement 31, fixing bolt holes 13 and 14 for inserting the fixing bolts 7 and 7 are formed in a portion facing the bumper stay 4b. .

Among them, the positioning hole 11 has a round hole shape as shown in FIG. 1, and restricts the movement of the inserted positioning bolt 6 in the vehicle width direction (X direction).
The positioning bolt 6 is formed to have an inner diameter substantially the same as the outer diameter.

Further, the fixing bolt holes 12 to 14 have X
The fixing bolt 7 has a horizontally elongated hole shape extending in the direction, is loosely fitted in the X direction, and is configured to regulate the movement in the vertical direction (Z direction).

Then, the nut members 10 ... Are screwed into the positioning bolts 6 and the fixing bolts 7 inserted into the positioning bolt holes 11 and the fixing bolt holes 12 to 14, respectively. The peripheral edges of the bolt holes 11 to 14 formed in the back surface 3d of the bumper reinforcement 3c are fastened to the mounting seat surfaces 4d and 4d of the bumper reinforcement 4c, and the bumper reinforcement 31 is fixed to the bumpers stays 4c and 4b. Is configured.

Next, the operation of the first embodiment will be described.

In the bumper mounting structure of the first embodiment thus configured, the bumper 3 extending along the vehicle width direction is provided.
When the 0 bumper reinforcement 31 is mounted on the vehicle body 15, the positioning bolt 6 and the fixing bolt 7 projecting from the bumpers 4b, 4c provided at the front ends of the side members 2, 2 on the vehicle body side. , Through the positioning bolt holes 11 and the fixing bolt holes 12 to 14, and at the tips of the positioning bolts 6 and the fixing bolts 7 ...
The nut members 10 ... Are screwed together.

By screwing the nut members 10 ..., the peripheral edges of the bolt holes 11 to 14 formed in the back surface 3d of the bumper reinforcement 31 are fastened to the mounting seat surfaces 4d and 4d of the bumpers 4c and 4b. , The bump pasty 4
The bumper reinforcement 31 is fixed to c and 4b.

At this time, the positioning in the vehicle width direction X is performed by restricting the position in the vehicle width direction X when the positioning bolt 6 is inserted into the positioning bolt hole 11 so that the bumper is attached to the vehicle body 15. The reinforcement 31 is attached.

Therefore, the bumper reinforcement 31 can be mounted on the vehicle body 15 with good positioning accuracy.

Further, as shown in FIG. 5, when the load F is applied to the bumper reinforcement 31, the slits 2 formed on the periphery of the mounting seat surface 4d of the positioning bolt 6 are formed.
The bridge portions 23, 23 formed by 2, 2 are deformed or sheared by the input of the load Fx in the vehicle width direction, and the load in the vehicle width direction is released.

At this time, the fixing bolts 7 inserted into the fixing bolt holes 12 to 14 slide in the vehicle width direction X while being guided in the vertical direction Z in the fixing bolt holes 12 ... Moving.

Therefore, of the loads F applied to the bumper reinforcement 31, all of the load Fx in the vehicle width direction is absorbed by the sliding movement of the bumper reinforcement 31 and is not transmitted to the bumpers stays 4b and 4c. .

Therefore, the bumper reinforcement 31
FIG. 6 shows only the load Fy applied to the vehicle in the front-rear direction.
As shown in, by causing a desired deformation such as a shaft crush deformation on the bumper stays 4b and 4c or the side members 2 and 2,
This load F can be absorbed.

Therefore, as shown in FIG. 3, even if the camber angle θ2 substantially the same as the camber angle θ1 of the central portion 3a of the bumper fascia 3b is formed in the central portion 31a of the bumper reinforcement 31, the input F Only the component force Fy in the Y direction is applied to the side members 2, 2 of the vehicle body 15 via the bumpers stays 4c, 4b and is not deformed outward in the vehicle width direction as in the conventional case.

Then, the restoration is also performed on the bump pasties 4b and 4c.
Since the original state can be obtained by replacing only the side members 2 and 2, the side members 2 and 2 of the vehicle body 15 need not be repaired, and the cost can be reduced.

[0059]

Second Embodiment FIGS. 7 to 9 show a vehicle bumper mounting structure according to the second embodiment. In addition, the same or equivalent portions as those in the first embodiment will be described with the same reference numerals.

First, the structure will be described. FIG. 7 shows the structure in the vicinity of the bumper stay 4a on the right side of the vehicle having the positioning portion in this bumper mounting structure.

On the mounting seat surface 4d of the bumper stay 4a, a positioning bolt 6 as a vehicle width direction positioning portion and a fixing bolt 7 are formed in a line in the X direction toward the front of the vehicle. ing.

On the other hand, of the bumper reinforcement 31, the positioning bolt 6 is inserted in the vicinity of the right end portion of the rear surface portion 3d facing the mounting seat surface 4d of the bumper stay 4a to regulate the position in the vehicle width direction. Positioning bolt hole 1
11 and a fixing bolt hole 12 are formed.

Of these, the positioning hole 111 has a round hole shape, and the holding hole 12 has a horizontally elongated hole shape extending in the X direction.

Around the positioning hole 111, a pair of left and right semi-arcuate slits 122, 122 as weakening means are formed.
The disk-shaped seat surface 124 around the positioning hole 111 into which the positioning bolt 6 is inserted is formed by a pair of upper and lower bridge-shaped portions 123, 123 formed between the upper and lower edges of 112.
It is connected to the back surface portion 3d and is supported so as to be deformable by a load input in the vehicle width direction.

Next, the operation of the vehicle bumper mounting structure of the second embodiment will be described.

In the vehicle bumper mounting structure according to the second embodiment, when the bumper reinforcement 131 is mounted on the vehicle body, the positioning bolt 6 is inserted into the positioning bolt hole 111 and the positioning bolt hole 12 is also inserted.
The fixing bolt 7 is inserted into the
The nut members 10 and 10 are screwed together.

And by this screwing. The peripheral edges of the disk-shaped member 124 and the fixing bolt hole 12 are fastened to the seat surface 4d of the bumper stay 4a.

Next, in the same manner as in FIG. 5 of the first embodiment, when a load F is input to the bumper reinforcement 131, the bridge-shaped member 12 that supports the disc-shaped member 124.
3, 123 is deformed or sheared as shown in FIGS. 8 and 9 to be separated from the surrounding back surface portion 3d.

Therefore, the load Fx in the vehicle width direction is not released to the positioning bolt 6 by this deformation or shearing. Further, the fixing bolts 7 ... Slide in the vehicle width direction X while being guided in the vertical direction Z in the fixing bolt holes 12 ...

Therefore, the bumper reinforcement 131
The load Fx in the vehicle width direction of the load F applied to the vehicle is absorbed by the sliding movement of the bumper reinforcement 31 and is not transmitted to the bumper stay 4a and is applied to the bumper reinforcement 131 in the vehicle longitudinal direction. A desired deformation such as axial crush deformation is generated in the bumper stay 4a or the side member 2 only by the load Fy of
This load F can be absorbed.

Depending on the magnitude of the input load, the repair can be restored to the original state by only replacing the bumper reinforcement 131. Therefore, the side member of the vehicle body 15 which is opened outward as in the conventional case. It is possible to reduce the cost without needing the repair of 2 and 2.

Other structures, functions, and effects are the same as or equivalent to those in the first embodiment, and therefore description thereof will be omitted.

[0073]

[Third Embodiment] FIG. 10 shows a vehicle bumper mounting structure according to a third embodiment of the present invention.

The same or equivalent parts as those in the first and second embodiments will be described with the same reference numerals.

First, the structure will be described. FIG. 10 shows the structure in the vicinity of the bumper stay 4e on the right side of the vehicle having the positioning portion in this bumper mounting structure.

On the mounting seat surface 4d of the bumper stay 4e, a positioning bolt 16 as a vehicle width direction positioning portion and a fixing bolt 7 are provided so as to project toward the front of the vehicle.

Of these, the shaft portion 16 of the positioning bolt 16
a Inner side surface 16b near the base near the center line of the vehicle front-rear direction
A notch 16c as a weakening means is formed in the notch.

Next, the operation of the vehicle bumper mounting structure of the third embodiment will be described.

In the third embodiment, the positioning bolt 1
A notch 16c is formed in a notch on an inner side surface 16b near the center line of the vehicle in the front-rear direction near the root of the shaft portion 16a of No. 6.

Therefore, when a load is applied in the vehicle width direction X,
When the shaft portion of the positioning bolt 16 is bent from the notch portion 16c and the load is further large, the shaft portion 16a is sheared and separated from the notch portion 16c, so that the load in the vehicle width direction X is reduced. Let it escape.

Therefore, a desired deformation such as a shaft crush deformation is generated in the side members 2, 2 and the like only by the load applied to the bumper reinforcement 3 in the vehicle front-rear direction to absorb the load. Can be done.

Other structures, functions, and effects are the same as or equivalent to those of the first and second embodiments, and therefore description thereof will be omitted.

Although the first to third embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to those of the first to third embodiments, and the gist of the present invention is not limited. Design changes that do not deviate are included in the present invention.

For example, all of the first to third embodiments are the front bumper mounting structure of the automobile, but by applying the present invention to the rear bumper mounting structure, a rear impact or a light impact to the extent that the bumper reinforcement is deformed. It is possible to obtain a rear bumper mounting structure that allows a side member of a vehicle body to absorb a desired deformation even if a force in the vehicle front-rear direction due to a collision or the like is received.

[0085]

As described above, according to the first aspect, the bumper reinforcement extending along the vehicle width direction is positioned in the vehicle width direction by the vehicle width direction positioning portion for positioning in the vehicle width direction. The position is regulated and it is mounted on the vehicle body.

Therefore, the bumper reinforcement can be mounted on the vehicle body with good positioning accuracy.

When a load is applied to the bumper reinforcement, the fragile means provided in the vehicle width direction positioning portion is deformed by the load input in the vehicle width direction to release the load in the vehicle width direction.

Therefore, a desired deformation of the vehicle body side member such as axial crush deformation can be generated only by the load applied to the bumper reinforcement in the vehicle front-rear direction, and the load can be absorbed.

Further, in the vehicle bumper mounting structure according to the present invention, since the weakening means is constituted by a slit formed on the peripheral edge of the mounting seat surface or the peripheral edge of the bolt hole, the mounting seat surface of the mounting seat surface is formed. When a load in the vehicle width direction is applied to the peripheral edge or the bolt hole peripheral edge, the slit peripheral edge is deformed by the load input in the vehicle width direction, and the load in the vehicle width direction is released.

Further, according to the third aspect of the invention, the cutout portion is formed in the shaft portion of the bolt member provided on either the vehicle body side or the bumper reinforcement side. Therefore, when a load is applied in the vehicle width direction, the cutout portion bends to release the load in the vehicle width direction.

Therefore, in practical use, it is possible to generate a desired deformation of the member on the vehicle body side, such as a shaft crush deformation, only by the load applied to the bumper force in the vehicle front-rear direction to absorb the load. Exert a beneficial effect.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of a main part of an automobile having a vehicle bumper mounting structure according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view for explaining a configuration near a bumper stay on the front right side of the automobile in the vehicle bumper mounting structure of the first embodiment.

FIG. 3 is a partial cross-sectional plan view illustrating a configuration near a bumper stay in the vehicle bumper mounting structure of the first embodiment.

FIG. 4 is an exploded perspective view for explaining a configuration in the vicinity of a bumper stay on the front left side of the automobile in the vehicle bumper mounting structure of the first embodiment.

FIG. 5 is a partial cross-sectional plan view illustrating the configuration in the vicinity of the bumper stay before load input in the vehicle bumper mounting structure of the first embodiment.

FIG. 6 is a partial cross-sectional plan view for explaining the deformation in the vicinity of the bumper stay after the load is input in the vehicle bumper mounting structure of the first embodiment.

FIG. 7 is an exploded perspective view illustrating a configuration in the vicinity of a bumper stay that illustrates a configuration of a main part in the vehicle bumper mounting structure of the second embodiment.

FIG. 8 is a cross-sectional view taken along line BB in FIG. 7 for explaining the sheared state immediately after inputting a load in the vehicle bumper mounting structure of the second embodiment.

FIG. 9 is a cross-sectional view taken along line BB in FIG. 7 for explaining the shearing state due to load input in the vehicle bumper mounting structure of the second embodiment.

FIG. 10 is a partial cross-sectional plan view showing a configuration in the vicinity of a bumper stay on the right front side of the vehicle for explaining the configuration of a main part in the vehicle bumper mounting structure of the third embodiment.

FIG. 11 is a partial cross-sectional plan view showing the configuration of a conventional vehicle bumper mounting structure.

FIG. 12 shows a conventional vehicle bumper mounting structure, which is indicated by C in FIG.
It is a rear view of the bumper reinforcement in the position which follows the C line.

FIG. 13 is a schematic diagram for explaining how the input of the load F is vector-divided into component forces Fx and Fy and transmitted to the bumper stay in the conventional vehicle bumper mounting structure.

FIG. 14 is a conventional vehicle bumper mounting structure, in which the component force Fx is applied.
It is a schematic diagram which showed the influence of by the deformation | transformation of a side member.

[Explanation of symbols]

X vehicle width direction Y vehicle front-back direction 2 Side members (car body) 3d rear part 4c bump pastay 4d Mounting surface Vehicle width direction positioning part 6 Positioning bolt 11,111 Positioning bolt hole 10 Nut member 15 vehicles 16 Positioning bolt 16a shaft 16c Notch 30 bumpers 31.131 Bumper Reinforce Vulnerable means 22,22 slit 23.23 Bridge

Claims (3)

[Claims] 1. A vehicle in which a bumper reinforcement extending along the vehicle width direction is mounted on a vehicle body with its position in the vehicle width direction restricted by a vehicle width direction positioning portion that positions in the vehicle width direction. Bumper mounting structure for vehicle, wherein the vehicle width direction positioning portion has a weakening means that is deformable by a load input in the vehicle width direction. 2. The vehicle width direction positioning portion is provided on a bolt member projecting from a mounting seat surface provided on either the vehicle body side or the bumper reinforcement side, and the other facing the bolt member. And a fastening member having a bolt hole for inserting the bolt member to regulate the position in the vehicle width direction and a nut member screwed into the bolt member to fasten the periphery of the bolt hole to the mounting seat surface. The bumper mounting structure for a vehicle according to claim 1, wherein the fragile means is constituted by a slit formed in a peripheral edge of the mounting seat surface or a peripheral edge of the bolt hole. 3. The weakening means includes a notch formed in the vehicle width direction positioning portion, the notch being formed in a shaft portion of a bolt member provided on one of the vehicle body side and the bumper reinforcement side. The vehicle bumper mounting structure according to claim 1 or 2, further comprising: