JP6128339B2 - Vehicle frame structure - Google Patents

Description

  The present invention relates to a vehicle frame structure, and more particularly to an aluminum alloy vehicle frame structure having a substantially rectangular main closed section.

Conventionally, a crash can that can be axially compressed and deformed is provided at the tip of the front side frame made of high-strength steel plate, and a plurality of shock absorbing mechanisms that can be actively bent and deformed from the middle to the rear end of the front side frame. Is used to increase the amount of impact energy absorbed at the time of a collision, thereby protecting the occupant during a front collision (Patent Document 1).
In such an impact absorbing mechanism, since the impact load absorbed by the bending deformation of the front side frame occupies most of the total amount of energy absorption, the energy absorbing characteristic due to the bending deformation is greater than the energy absorbing characteristic due to the compressive deformation. ) Large impact on performance.

By the way, since the functional value such as running motion performance can be increased by promoting the reduction of the weight of the vehicle body, in recent years, a light aluminum alloy material has been used for a vehicle frame or the like.
In addition, an aluminum alloy vehicle frame having excellent ductility is excellent in productivity because it has a high degree of freedom in cross section and can be obtained by extrusion forming a light-weight and high-strength cross-sectional shape.

  The frame structure of Patent Document 2 includes an aluminum alloy front side frame front portion formed in a closed cross-section structure by extrusion molding, and a partition wall formed in a closed cross-section structure by extrusion molding and orthogonal to the vertical direction in the closed cross-section structure A front side frame rear portion made of aluminum alloy provided with a middle rib is formed, and a coupling portion between the front side frame front portion and the front side frame rear portion is formed along the middle rib position. Thereby, since the range in which the strength is locally reduced by welding can be held by the middle rib, the buckling of the wall surface in the out-of-plane direction due to the impact load is suppressed.

Japanese Patent No. 5104272 Japanese Patent Laid-Open No. 11-208517

In the shock absorbing mechanism disclosed in Patent Document 1, a load that cannot be absorbed mainly by the compression deformation of the crash can and the bending deformation of the front side frame among the input impact loads is a vehicle body component behind the front side frame. And transmitted to the passenger compartment.
In other words, when the impact load absorbed by the bending deformation is small, the longitudinal deformation stroke of the front side frame, which is necessary for absorbing the shock, the so-called crash stroke becomes longer, reducing the degree of freedom in vehicle design and increasing the vehicle weight. There is a risk of inviting.

The present inventor conducted an analysis by CAE (Computer Aided Engineering) on the mechanism of the deformation behavior of a frame having a vertically long rectangular cross section when examining the above problems.
First, the basic concept of this analysis will be described.
As shown in FIG. 14, a closed cross-section steel frame model M extending in the longitudinal direction and a load applying means T for bending the axis of the frame model M in a state where both ends of the frame model M are sandwiched are prepared. Then, the displacement of the load point P and the reaction force of the load point P were analyzed.
As shown in FIGS. 14, 15 (a), and 15 (b), the load applying means T is formed with a support portion Ta that can rotate about the pivot portion R and a load point P that applies a load. In addition, a support portion Tb that can be rotated while being displaced toward the support portion Ta side, and a straight line connecting the pivot portion R and the load point P is offset from the axis of the frame model M by 50 mm. In addition, each wall part of the frame model M includes a compression side wall part Ma to which a compressive load acts, a tension side wall part Mb to which a tensile load acts, an upper end wall part Mc and a lower end wall that connect the upper and lower end parts of each wall part, respectively. Part Md.

An analysis result will be described based on a correlation (FS characteristic) between a load that can be supported by the frame model M and a stroke by which the frame model M is deformed.
As shown in FIG. 16, in the closed cross-section frame extending in the longitudinal direction, a maximum (allowable limit) load of 26 kN that peaks at a predetermined displacement is generated, and the load is rapidly reduced after buckling.

The mechanism of this buckling occurrence is presumed as follows.
As shown in FIG. 17, an elastic buckling wave W is generated in the compression side wall portion Ma by applying a load exceeding the allowable limit, and this elastic buckling wave W propagates to the upper end wall portion Mc and the lower end wall portion Md. In addition, out-of-plane deformation occurs in the top wall portion Mc corresponding to the valley region m of the elastic buckling wave W in the compression side wall portion Ma and the mountain region n of the bottom wall portion Md. As a result, the upper end wall portion Mc and the lower end wall portion Md bulge out in the out-of-plane direction, and the compression side wall portion Ma is folded in two to buckle the closed cross-section frame. That is, by attenuating the elastic buckling wave W of the compression side wall portion Ma, the upper end wall portion Mc and the lower end wall portion Md, the allowable limit load is increased to the plastic region of the material, in other words, the performance possessed by the material is increased. EA can be increased effectively.

Therefore, in the elastic buckling wave W, the period is governed by the plate width of the compression side wall portion Ma, the upper end wall portion Mc, and the lower end wall portion Md, and the amplitude is governed by the plate thickness of each wall portion Ma, Mc, Md. Therefore, it is considered that the occurrence of elastic buckling can be suppressed by reducing the plate width of the compression side wall portion Ma and increasing the plate thickness of each wall portion Ma, Mc, Md. However, when the plate thickness of each wall portion Ma, Mc, Md is increased, the weight of the vehicle body and the cost of the closed cross-section frame itself increase, and the EA efficiency per unit mass (EA mass efficiency) of the closed cross-section frame is sufficient. There is a possibility that it cannot be improved.
If the plate width of the compression side wall portion Ma is simply reduced, the strength becomes insufficient as the main structural frame of the vehicle body. If the plate width of the compression side wall portion Ma is reduced and the plate widths of the upper end wall portion Mc and the lower end wall portion Md are increased. There is a possibility that the arrangement space of each member arranged in the engine room is disadvantageous.

  An object of the present invention is to provide a vehicle frame structure or the like having high EA mass efficiency while suppressing elastic buckling.

The frame structure for a vehicle according to claim 1 includes a compression side portion including a vertical compression side wall portion on which a compressive load acts, and a tension side portion including a vertical tension side wall portion on which a tensile load acts. In the aluminum alloy vehicle frame structure in which the upper and lower end portions of the side portion and the tensile side portion are joined to form a main closed cross section whose cross section perpendicular to the longitudinal direction is substantially rectangular, the compression side wall portion to the tensile side wall portion A plurality of horizontal partition wall portions that extend and form a plurality of sub-closed cross-sections that are adjacent to each other vertically within the main closed cross section, wherein b is the separation width of the adjacent horizontal partition wall portions, and the compression side wall portion The plurality of horizontal partition walls are formed so as to satisfy the relationship of 0.06 ≦ t / b ≦ 0.12, where t is the thickness of the plate.

In this vehicle frame structure, the aluminum alloy vehicle frame structure includes a plurality of horizontal partition walls disposed so as to form a plurality of sub-closed cross-sections adjacent in the vertical direction within the main closed cross-section. The aspect ratio of the sub-closed cross section can be adjusted to 1 or less while reducing the weight.
Thereby, elastic buckling can be suppressed by shortening the elastic buckling period of the compression side wall part accompanying width shortening, and the allowable limit load of a vehicle frame can be increased.
In addition, when the separation width of adjacent horizontal partition walls is b and the thickness of the compression side wall is t, a plurality of horizontal partition walls are formed so as to satisfy the relationship of 0.06 ≦ t / b ≦ 0.12. Since it is formed, the occurrence of buckling in the elastic region of the frame material can be avoided.

According to a second aspect of the present invention, in the first aspect of the present invention, one or a plurality of vertical partition walls are formed in the main closed section so as to be orthogonal to the longitudinal direction and integrally formed with the compression side wall. It is characterized by that.
According to this configuration, the upper end wall portion and the lower end wall portion are pulled by one or a plurality of vertical partition walls, and therefore, the out-of-plane direction of the upper end wall portion and the lower end wall portion due to the elastic buckling wave propagated from the compression side wall portion. Can be suppressed.

The invention of claim 3 is characterized in that, in the invention of claim 2, the compression side portion and the tension side portion are each made of a cast product.
According to this configuration, a structure including a plurality of horizontal partition walls and one or more vertical partition walls disposed in a main closed cross section that is difficult to be extruded is formed integrally with the compression side wall by a simple method. can do.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, a bead that is orthogonal to the longitudinal direction and is recessed into the main closed cross section is formed in the compression side wall, and the vertical partition wall is formed in the bead. It is characterized by being joined.
According to this configuration, since the out-of-plane deformation of the upper end wall portion and the lower end wall portion can be suppressed, the vehicle frame can be bent and deformed starting from the bead position while suppressing a decrease in the allowable limit load of the vehicle frame. . Moreover, after the buckling of the compression side wall portion, the collapsed vertical partition wall portion is interposed between the compression side wall portion and the tensile side wall portion to suppress cross-sectional collapse at a position corresponding to the bead, thereby increasing EA efficiency. Can do.

  According to the vehicle frame structure of the present invention, high EA mass efficiency can be ensured while suppressing elastic buckling.

It is the side view which looked at the front side frame concerning Example 1 from the engine room inside. It is a top view of a right front side frame. It is the III-III sectional view taken on the line of FIG. It is a perspective view of an outer member. It is a perspective view of an inner member. It is principal part perspective sectional drawing of a front-end | tip part. It is a principal part cross-sectional perspective view of a 1st outer part. It is a principal part cross-sectional perspective view of a 3rd outer part. It is a schematic diagram which shows the state of the vehicle before the input of a front impact load. It is a schematic diagram which shows the state of the vehicle after the input of a front impact load. It is a table | surface which shows a 1st analysis result. It is a table | surface which shows a 2nd analysis result. It is a part of table | surface which shows a 3rd analysis result. It is the remainder of the table | surface which shows a 3rd analysis result. It is explanatory drawing of the analysis method which concerns on the deformation | transformation behavior of a closed cross-section frame. It is a deformation | transformation behavior of a closed cross-sectional frame, Comprising: (a) shows the state figure before giving a load, (b) has shown the state figure after giving a load. It is a graph which shows the FS characteristic of the conventional closed section frame. It is a figure explaining elastic buckling of a closed section frame.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The following description exemplifies a case where the present invention is applied to a front side frame of a vehicle, and does not limit the present invention, its application, or its use.
In the figure, the direction of arrow F is the front, the direction of arrow L is the left, and the direction of arrow U is the top.

Embodiment 1 of the present invention will be described below with reference to FIGS.
First, the front body structure in which the front side frame is installed will be briefly described.
As shown in FIG. 1, a vehicle V includes a dash panel 1 that partitions an engine room E and a vehicle compartment by extending in a vertical direction and a vehicle width direction, and a front side frame that extends in the vehicle body front-rear direction at a front position of the dash panel 1. 2, a suspension tower 3 standing in a tower shape at a side position of the front side frame 2, and an apron 4 for connecting the suspension tower 3 and the above-described dash panel 1 by extending in the vertical direction and the vehicle body longitudinal direction. And an apron rain member 5 extending in the longitudinal direction of the vehicle body at the upper end of the apron portion 4. In addition, since it is a right-and-left object structure, it mainly demonstrates the vehicle body right side structure, and abbreviate | omits description about the vehicle body left side structure.

A crash can 6 is installed at the front end of the front side frame 2 to compress and deform (axially compress) when receiving a front impact load to absorb part of the collision energy.
A substantially cylindrical engine mount 7 is installed in the front-rear direction center of the front side frame 2, and a power unit (not shown) is elastically supported by the engine mount 7. A mount attachment rain 8 is provided in the front side frame 2 below the engine mount 7 in order to increase the attachment rigidity of the engine mount 7. A sub-frame mounting bracket 9 for attaching a suspension sub-frame (not shown) is joined and fixed to the rear lower surface of the front side frame 2.

Next, the front side frame 2 will be described in detail.
As shown in FIGS. 2 and 3, the front side frame 2 is formed of an aluminum alloy material (5000 series) and has a main rectangular cross-section C that is long in the vertical direction and has a substantially rectangular shape with a so-called aspect ratio larger than an aspect ratio. It is composed. The front side frame 2 has a front end portion 2a, a front midway portion 2b continuous to the rear side of the front end portion 2a, and a rear side continuous to the rear side of the front side midway portion 2b according to the function of each region in the front-rear direction. A side intermediate portion 2c and a base end portion 2d connected to the rear side of the rear intermediate portion 2c are provided.

  The front end portion 2a is formed so that the front end side portion is deformed by axial compression and the rear end side portion is bent outwardly by the first bead 11f extending vertically when the front collision occurs. It is formed to support. Further, the rear middle portion 2c is formed so that the middle portion is bent and deformed by the second bead 23f extending vertically when the front collision occurs, and the rear end portion supports the subframe mounting bracket 9, and the proximal end portion 2d is formed such that, during a front collision, the middle part is bent outwardly by a third bead 14f extending vertically and the rear end side part is fixed to the dash panel 1.

As shown in FIGS. 2 to 5, the front side frame 2 is divided into two parts by an outer member 10 formed by casting and an inner member 20 formed by casting.
As shown in FIG. 4, the outer member 10 includes a first outer portion 11 (compression side portion) constituting the right half portion of the tip portion 2 a and a second outer portion 12 constituting the right half portion of the front halfway portion 2 b. And the third outer portion 13 (tensile side portion) constituting the right half of the rear halfway portion 2c and the fourth outer portion 14 (compression side portion) constituting the right half of the base end portion 2d. Is formed.

The first outer portion 11 will be described.
As shown in FIGS. 2 to 4, 6, and 7, the first outer portion 11 includes a compression side wall portion 11 a along a plane substantially orthogonal to the left-right direction, and 2 extending leftward from the compression side wall portion 11 a. One vertical partition wall portion 11b, an upper end wall portion 11c extending leftward from the upper end portion of the compression side wall portion 11a, a lower end wall portion 11d extending leftward from the lower end portion of the compression side wall portion 11a, and the like are integrally provided. .

The compression side wall part 11a is formed in predetermined thickness t, for example, 2.5 mm.
The compression side wall part 11a is integrally provided with three horizontal partition wall parts 11e and a first bead part 11f. The three horizontal partition walls 11e form four sub closed cross sections c that are adjacent to each other in the main closed cross section C and extend in the front-rear direction. These four sub-closed cross sections c are formed in a cross-sectional horizontally long rectangular shape, and the aspect ratio is set to be less than 1.

The three horizontal partition walls 11e are each formed to a predetermined thickness, for example, 2.0 mm.
The three horizontal partition walls 11e extend from the compression side wall 11a to the left substantially horizontally and divide the upper end wall 11c and the lower end wall 11d into a substantially uniform separation width b.
The separation width b (vertical pitch) of the horizontal partition wall 11e adjacent to the thickness t of the compression side wall 11a is set so as to satisfy the following expression (1).
0.05 ≦ t / b ≦ 0.12 (1)

The first bead part 11f is formed so as to be substantially orthogonal to the front-rear direction over the vertical direction of the compression side wall part 11a. The first bead portion 11f is recessed on the main closed section C side.
Since the EA efficiency increases as the bead width a (the front-rear width of the bead) decreases, the bead width a is set to 1.6 mm in this embodiment in consideration of productivity.
As a result, when a predetermined compressive load is applied to the compressed side wall portion 11a from the front, the compressed side wall portion 11a is bent to the right side (the vehicle width direction outer side) with the first bead portion 11f as a starting point.

As shown in FIGS. 4, 6, and 7, the two vertical partition walls 11 b are disposed in the main closed section C so as to be along the plane orthogonal to the front-rear direction, and are integrally formed with the compression side wall 11 a. Has been.
The front vertical partition wall portion 11b extends to the left from the compression side wall portion 11a, and the rear vertical partition wall portion 11b extends to the left from the first bead portion 11f to which the right end portion is joined.
The separation width L (front / rear pitch) of the two vertical partition walls 11b is set to 30 to 50 mm from the viewpoint of EA efficiency. When the first bead portion 11f is bent and deformed by the two vertical partition wall portions 11b, out-of-plane deformation that occurs in the upper end wall portion 11c and the lower end wall portion 11d can be suppressed.
In addition, the separation width L of the vertical partition wall 11b can be set by the following equation (2).
0.7 (a / 2 + b) ≦ L ≦ 1.7 (a / 2 + b) (2)

  The upper end wall portion 11c and the lower end wall portion 11d include an upper flange portion 11g and a lower flange portion 11h, respectively. The upper flange portion 11g extends upward from the left end portion of the upper end wall portion 11c, and the lower flange portion 11h extends downward from the left end portion of the lower end wall portion 11d.

  As shown in FIGS. 2 and 4, the second outer portion 12 is formed in a substantially hat-shaped cross section, and is located on the right side wall portion 12 a along a plane substantially orthogonal to the left-right direction, and left from the upper end portion of the right side wall portion 12 a. And a lower end wall portion 12c extending leftward from a lower end portion of the right side wall portion 12a. The upper end wall portion 12b and the lower end wall portion 12c have an upper flange portion 12d and a lower flange portion 12e, respectively. The upper flange portion 12d extends upward from the left end portion of the upper end wall portion 12b, and the lower flange portion 12e is the lower end wall portion. It is formed to extend downward from the left end of 12c.

Next, the third outer portion 13 will be described.
The third outer portion 13 is constituted by a tensile side wall portion 13a along a surface substantially orthogonal to the left-right direction. This tension side wall part 13a is formed in predetermined thickness, for example, 3.0 mm.
As shown in FIGS. 2 and 4, the tensile side wall portion 13a includes four engaging portions 13b extending in the front-rear direction, an upper flange portion 13c extending upward from the upper end portion of the tensile side wall portion 13a, and the tensile side wall portion 13a. The lower flange part 13d extended downward from the lower end part of this is integrally provided.

As shown in FIG. 8, each of the four engaging portions 13b has a pair of upper and lower engaging ribs 13e and an engaging groove 13f formed between the engaging ribs 13e.
These engagement ribs 13e protrude from the tension side wall part 13a into the main closed section C (left side) by a predetermined width, for example, 10 mm. The protrusion width H of the engagement rib 13e is set in the range of 5 to 15 mm from the viewpoint of EA efficiency.

As shown in FIGS. 2 and 4, the fourth outer portion 14 includes a compression side wall portion 14a, three vertical partition wall portions 14b, an upper end wall portion 14c having an upper flange portion 14g, and a lower flange portion 14h. The lower end wall portion 14d and the like are integrally provided. The compression side wall part 14a is integrally provided with two horizontal partition wall parts 14e and a third bead part 14f recessed into the main closed section C side.
The separation width b of the lateral partition wall portion 14e adjacent to the thickness t of the compression side wall portion 14a is set so as to satisfy the formula (1), and the separation width L of the three vertical partition wall portions 14b is 30 to 50 mm. Is set. As a result, when a predetermined compressive load is applied to the compressed side wall portion 14a from the front, the compressed side wall portion 14a is bent to the right from the third bead portion 14f as a starting point.
The fourth outer portion 14 is configured in substantially the same manner as the first outer portion 11 except for the number of vertical partition wall portions 14b and horizontal partition wall portions 14e.

Next, the inner member 20 will be described.
As shown in FIGS. 2 and 5, the inner member 20 includes a first inner portion 21 (tensile side portion) that constitutes the left half portion of the tip portion 2a and a second half portion that constitutes the left half portion of the front halfway portion 2b. Inner portion 22, third inner portion 23 (compression side portion) constituting the left half of rear halfway portion 2 c, and fourth inner portion 24 (tensile side portion) constituting the left half of proximal end portion 2 d And are integrally formed.

The first inner portion 21 will be described.
The 1st inner part 21 is comprised by the tension | pulling side wall part 21a along the surface substantially orthogonal to the left-right direction. This tension side wall part 21a is formed in predetermined thickness, for example, 3.0 mm. The tensile side wall portion 21a includes three engaging portions 21b extending in the front-rear direction, an upper flange portion 21c extending upward from the upper end portion of the tensile side wall portion 21a, and a lower flange portion extending downward from the lower end portion of the tensile side wall portion 21a. 21d is integrally provided.

As shown in FIG. 3, the three engaging portions 21b are configured to be engageable with the left end portions of the three horizontal partition wall portions 11e, respectively. The engaging portions 21b have a pair of upper and lower engaging ribs 21e and an engaging groove 21f formed between the pair of engaging ribs 21e. The first inner portion 21 is configured in substantially the same manner as the third outer portion 13 except for the number of engaging portions 21b.
By joining the upper flange portion 21c and the upper flange portion 11g and joining the lower flange portion 21d and the lower flange portion 11h, a tip portion 2a having a main closed cross section C constituted by four sub closed cross sections c is formed. The Thereby, the left end part of the horizontal partition wall part 11e and the engaging part 21b are engaged, and the right surface part of the tensile side wall part 21a and the left end part of the vertical partition wall part 11b are opposed to each other with a slight gap therebetween. doing.

The 2nd inner part 22 is comprised by the left side wall part 22a.
The left side wall portion 22a includes an upper flange portion 22b extending upward from the upper end portion and a lower flange portion 22c extending downward from the lower end portion.
As shown in FIGS. 2, 4 and 5, the mount mounting rain 8 is disposed by joining the upper flange portion 22b and the upper flange portion 12d and joining the lower flange portion 22c and the lower flange portion 12e. A front halfway portion 2b having a main closed section C is formed.

Next, the third inner portion 23 will be described.
As shown in FIGS. 2 and 5, the third inner portion 23 includes a compression side wall portion 23a, three vertical partition wall portions 23b, an upper end wall portion 23c having an upper flange portion 23g, and a lower flange portion 23h. A lower end wall 23d and the like are integrally provided. The compression side wall part 23a is integrally provided with four horizontal partition wall parts 14e and a second bead part 23f recessed into the main closed section C side.
The separation width b of the horizontal partition wall portion 23e adjacent to the thickness t of the compression side wall portion 23a is set so as to satisfy the formula (1), and the separation width L of the three vertical partition wall portions 23b is set to 30 to 50 mm. Is set. As a result, when a predetermined compressive load is applied to the compressed side wall portion 23a from the front, the compressed side wall portion 23a is bent to the left (inward in the vehicle width direction) starting from the second bead portion 23f. The third inner portion 23 is configured in substantially the same manner as the first outer portion 11 (fourth outer portion 14) except for the number of vertical partition wall portions 23b and horizontal partition wall portions 23e.

  By joining the upper flange portion 23g and the upper flange portion 13c and joining the lower flange portion 23h and the lower flange portion 13d, a rear intermediate portion 2c having a main closed section C composed of five sub closed sections c is obtained. It is formed. As a result, the right end portion of the horizontal partition wall portion 23e and the engaging portion 13b are engaged, and the left surface portion of the tensile side wall portion 13a and the right end portion of the vertical partition wall portion 23b are in contact with each other with a slight gap therebetween. doing.

  The 4th inner part 24 is comprised by the tension | pulling side wall part 24a along the surface substantially orthogonal to the left-right direction. This tension side wall part 24a is formed in predetermined thickness, for example, 3.0 mm. The tensile side wall portion 24a includes two engaging portions 24b extending in the front-rear direction, an upper flange portion 24c extending upward from the upper end portion of the tensile side wall portion 24a, and a lower flange portion extending downward from the lower end portion of the tensile side wall portion 24a. 24d is integrally provided.

The two engaging portions 24b are configured to be engageable with the left end portions of the two horizontal partition wall portions 14e, respectively. These engagement portions 24b have a pair of engagement ribs 24e and an engagement groove 24f formed between the pair of engagement ribs 24e. The fourth inner portion 24 is configured in substantially the same manner as the third outer portion 13 (first inner portion 21) except for the number of engaging portions 24b.
By joining the upper flange portion 24c and the upper flange portion 14g and joining the lower flange portion 24d and the lower flange portion 14h, a base end portion 2d having a main closed cross section C formed by three sub closed cross sections c is formed. Is done. Thereby, the left end part of the horizontal partition wall part 14e and the engaging part 24b are engaged, and the right surface part of the tensile side wall part 24a and the left end part of the vertical partition wall part 14b are opposed to each other with a slight gap therebetween. doing.

Next, the deformation behavior when the vehicle V receives a front impact load will be described based on the schematic diagrams of FIGS. 9 and 10.
In the schematic diagram of FIG. 9, F is a front frame body composed of a front side frame and a crash box, D is a dash panel, M is a connection reinforcing member, I is an inner side composed of a dash lower cross and a member member provided in the tunnel portion. A load transmission body, U is an upper connecting member, Q (hatching area) is a mount mounting rain, R (hatching area) is a subframe mounting bracket, and T is a front tire.

In addition, on the front frame body F, a plurality of points extending substantially linearly in the front-rear direction are set for convenience so that the positional relationship after deformation can be easily understood.
The first point P 1 is the front end position of the crash can 6, the second point P 2 is the front end position of the front side frame 2, the third point P 3 is the position where the first bead portion 11 f is formed, and the fourth point P 4 is after the mount attachment rain 8. The end position, the fifth point P5 indicates the formation position of the second bead portion 23f, and the sixth point P6 indicates the formation position of the third bead portion 14f.

When the load Z is applied, the front frame body F actively absorbs impact energy by causing compression deformation and bending deformation in the vehicle width direction.
As shown in FIG. 10, when the collision body collides with the front frame body F, axial compression deformation occurs in the area from the first point P1 to the second point P2 of the front frame body F and the rear vicinity area of the second point P2. Arise.
At the third point P3, the first bead portion 11f causes bending deformation (outward bending deformation) to the outside in the vehicle width direction. Between the third point P3 and the fourth point P4, there is a mount attachment rain Q or the like and deformation cannot be caused. Therefore, once between the second point P2 and the third point P3, the vehicle width direction is once inside. Bending deformation (inward bending deformation) is generated, and bending deformation is performed outward in the vehicle width direction at the third point P3.

At the fifth point P5, the second bead portion 23f causes bending deformation (inward bending deformation) inward in the vehicle width direction. In the vicinity of the rear side of the fifth point P5, the subframe is mounted and fixed by the subframe mounting bracket R, and the frame rigidity is increased in order to distribute the load at the rear position thereof. Deformation is promoted. At the sixth point P6, the third bead portion 14f is bent outwardly in the vehicle width direction.
As described above, the third point P3 and the sixth point P6 are sufficiently deformed by bending outward in the vehicle width direction, and the fifth point P5 is sufficiently deformed by bending inward in the vehicle width direction. High EA efficiency is secured.

Next, functions and effects of the vehicle frame structure of the present embodiment will be described.
First, the correlation between the thickness t of the compressed side wall portion 11a (14a, 23a) and the separation width b of the adjacent horizontal partition wall portion 11e (14e, 23e) and the EA efficiency is verified.
The front side frame 2 having a main closed cross section C constituted by a plurality of sub closed cross sections c can be regarded as an assembly of a single rectangular cross section (sub closed cross section c) frame. That is, the EA efficiency of the front side frame 2 can be evaluated by verifying the EA efficiency of the rectangular section frame alone. Therefore, a compression bending model having a single rectangular cross section was prepared, and a first analysis by CAE (Computer Aided Engineering) was performed.

The preconditions for the first CAE analysis will be described.
A compression bending model with material properties of a 5000 series aluminum alloy material assumed to be high ductility and not to break is prepared, and the seat is based on the correlation (FS characteristics) between the load that can be supported by the model and the stroke at which the model is deformed. The bending mode and load characteristics were verified (see FIGS. 14 and 15).
In the compression bending model, the cross-section (vertical) height is fixed to 50 (mm), and the cross-section (left-right) width d regarded as the separation width b is 20, 25, 30, 40, 50, 75 (mm), Long model A11-A64 which changed board thickness t into 1.0, 2.5, 3.0, 3.5 (mm) was used.
The buckling modes to be judged are the elastic buckling mode in which the compression bending model buckles in the elastic region before the yield point of the aluminum alloy material, the plastic buckling mode in which the compression bending model buckles in the plastic region after the yield point, compression The bending model was classified into a fully elastic-plastic mode where all plastic bending moments occur without buckling.

FIG. 11 shows the analysis result by CAE.
The vertical axis of each graph showing the FS characteristics of the models A11 to A64 is the load (kN), and the horizontal axis is the stroke (mm).
As shown in FIG. 11, the models A21, A31, A41, A51, A61 to A63 having t / d of 0.040 or less generate an elastic buckling mode in which the load drops suddenly, so that the performance possessed by the material is effective. It has not been used for. Although the model A64 with t / d of 0.047 is a plastic buckling mode, the load drop due to buckling is large, and there is a problem in EA (Energy Absorption) efficiency. As a result, in the classification of elastic buckling mode, plastic buckling mode, and complete elasto-plastic mode, when t / d is 0.05 or more, the performance of the material can be used effectively, and compression is performed in plastic buckling mode. It can be seen that bending can be performed.
Although the model A11 has an elastic multi-stage buckling mode in which a plurality of points buckle in the elastic region, although t / d is 0.050, the elastic buckling mode, the plastic buckling mode, and the fully elastic-plastic mode Since it does not belong to any of the categories, it is excluded from this classification.

When the model A44 has a t / d of 0.088, it is possible to perform compression bending in a completely elastic-plastic mode without causing buckling. When the model A23 has a t / d of 0.120, the FS It is possible to carry out a fully elastic-plastic mode compression bending with a substantially flat characteristic load.
Thereby, when t / d is 0.088 or more, occurrence of buckling can be avoided while utilizing material performance, and when t / d exceeds 0.120, EA efficiency can be saturated. I understand.
Therefore, when t / d is 0.06 or more and 0.12 or less, generation of elastic buckling can be avoided and high EA mass efficiency (EA efficiency per unit mass) can be ensured.
Further, when t / d is 0.088 or more and 0.12 or less, the complete elastic-plastic mode can be executed, and higher EA mass efficiency can be secured.

Next, in order to verify the correlation between the horizontal partition wall and the EA efficiency, a compression bending model having a rectangular cross section was prepared, and a second analysis by CAE was performed.
The preconditions for the second CAE analysis will be described.
Similar to the first CAE analysis, long compression bending models X1 to X6 having material characteristics of a 5000 series aluminum alloy material were prepared, and load characteristics were verified based on the FS characteristics of each model.

  The compression bending model has X1 (t / d = 0.06) in which one horizontal partition wall is bonded to both the tension and compression wall portions, and two horizontal partition walls are bonded to both the tension and compression wall portions. X2 (t / d = 0.09) X3 (t / d = 0.12) in which three horizontal partition walls are joined to both tensile and compressive wall parts, and four horizontal partition walls are both tensile and compressive X4 (t / d = 0.15) joined to the wall part, and an engagement part (engagement rib protrusion width H: 10 mm) formed on the tension side wall part by three lateral partition walls extending from the compression side wall part X5 engaged with X3, and X6 engaged with an engagement portion (engagement rib protrusion width H: 10 mm) in which three lateral partition wall portions extending from the tensile side wall portion were formed with compression side wall portions were used.

FIG. 12 shows the analysis result by CAE.
From the analysis results of the models X1 to X4, although the EA of the model X4 having the four horizontal partition walls is the highest, the model X3 having the three horizontal partition walls has the highest EA mass efficiency, considering the mass. I understand that. Further, from the analysis results of models X5 and X6, the EA mass efficiency of model X5 in which the engagement portion is formed on the tensile side wall is about 1.3 times the EA mass efficiency of model X6 in which the engagement portion is formed on the compression side wall. It turns out that it is. The vertical axis of the FS characteristic is the load (kN), and the horizontal axis is the stroke (mm).
In the model X5, as the bending deformation progresses, the horizontal partition wall portion is pressed against the tensile side wall portion, so that the horizontal partition wall portion contributes to the improvement of the strength of the entire model. On the other hand, in the model X6, since the horizontal partition wall part is separated from the compression side wall part due to bending deformation, when the bending deformation proceeds, the engagement between the horizontal partition wall part and the engaging part is released, and the horizontal partition wall is released. The reason that the portion does not contribute to the improvement of the strength of the model is the reason for the decrease in EA efficiency. Furthermore, the tensile strength of the tension side wall portion itself can be improved by forming the engagement rib on the tension side wall portion.

Next, in order to verify the correlation between the bead and the EA efficiency, the correlation between the vertical partition wall and the EA efficiency, and the correlation between the protrusion width H of the engagement rib and the EA efficiency, a compression bending model having a rectangular cross section is used. Prepared and performed a third analysis by CAE.
The preconditions for the third CAE analysis will be described.
Similar to the first CAE analysis, long compression bending models Y1 to Y11 having material characteristics of 5000 series aluminum alloy materials were prepared, and the load characteristics were verified based on the FS characteristics of each model.

  In all the compression bending models Y1 to Y11, three sub-sections that extend in the direction from the compression side wall (thickness 2.5 mm) to the tension side wall (thickness 3.0 mm) and that are adjacent to each other in the vertical direction are three. Horizontal partition wall (thickness: 2.0 mm), three engagement parts that can be engaged with these three horizontal partition walls, respectively, and a vertically extending width recessed into the main closed cross section of the compression side wall A bead for bending deformation of 16 mm is provided. In the models Y1 and Y2, engagement ribs having a protruding width of 10 mm that can be engaged with the horizontal partition wall are formed. The model Y1 has a vertical partition wall portion omitted, and the model Y2 has a single vertical partition wall portion joined to a bead on the compression side wall portion. In the following description, the vertical partition wall portion is formed along a plane orthogonal to the longitudinal direction of the model, and is integrally formed with the compression side wall portion, the upper end wall portion, and the lower end wall portion.

Models Y3 to Y7 have an engagement rib with a protruding width of 10 mm that can be engaged with the horizontal partition wall, and the intermediate vertical partition wall joined to the bead on the compression side wall and the intermediate vertical partition wall between Three vertical partition walls, including a pair of left and right vertical partition walls sandwiched, are provided.
Model Y3 has an interval between adjacent vertical partition walls of 20 mm, model Y4 has an interval between adjacent vertical partition walls of 30 mm, and model Y5 has an interval of 40 mm between adjacent vertical partition walls. In the model Y6, the interval between the adjacent vertical partition walls is set to 50 mm, and in the model Y7, the interval between the adjacent vertical partition walls is set to 60 mm.
In the models Y8 to Y11, the interval between adjacent vertical partition walls is set to 30 mm.
Model Y8 is an engagement rib with a protrusion width H of 3 mm, Model Y9 is an engagement rib with a protrusion width H of 5 mm, Model Y10 is an engagement rib with a protrusion width H of 15 mm, and Model Y11 is an engagement rib with a protrusion width H of 20 mm. Each rib is formed.

FIG. 13A and FIG. 13B show the analysis results by CAE. The vertical axis of the FS characteristic is the load (kN), and the horizontal axis is the stroke (mm).
From the analysis results of the models Y1 and Y2, it can be seen that the EA mass efficiency of the model Y2 in which the vertical partition wall portion is formed is higher than the EA mass efficiency of the model Y1 in which the vertical partition wall portion is omitted.
This is because, when the bending deformation occurs starting from the bead, the vertical partition wall portion is connected to each of the upper end wall portion and the lower end wall portion, thereby suppressing the out-of-plane deformation.
Further, in the FS characteristic of model Y2, a rising portion where the load once dropped again rises was observed. This is because, when bending deformation occurs starting from the bead, the collapsed vertical partition wall part is interposed between the compression side wall part and the tension side wall part to suppress the cross-sectional collapse at the position corresponding to the bead. It is.

From the analysis results of the models Y3 to Y7, the EA mass efficiency of the models Y4 to Y6, in which the interval between the vertical partition walls is 30 to 50 mm, is higher than 2400 (kJ / kg). It can be seen that it is higher than the EA mass efficiency. In particular, the EA mass efficiency of the model Y4 having a distance of 30 mm between the vertical partition walls is the highest.
This is because the contribution rate of suppressing out-of-plane deformation by the vertical partition wall portion is reduced even if the position is too close or too far from the position corresponding to the bead that is the starting point of deformation.

From the analysis results of the models Y4, Y8 to Y11, the models Y4, Y9 and Y10 in which the protrusion width H of the engagement rib is 5 to 15 mm have an average load higher than 19.8 kN and an EA mass efficiency of 2500 (kJ / kg). ) Is higher than
Although the EA mass efficiency becomes higher as the protrusion width H of the engagement rib is smaller, there is a possibility that the engagement between the horizontal partition wall portion and the engagement portion is released and the horizontal partition wall portion does not contribute to the improvement in the strength of the model. If the protrusion width H exceeds 10 mm, mold design is difficult due to the hot water and the like, and productivity may be reduced.

According to the vehicle frame structure, in the aluminum alloy front side frame 2, a plurality of horizontal partition wall portions 11e arranged so as to form a plurality of sub-closed cross sections c adjacent in the vertical direction within the main closed section C. Since (23e, 14e) are provided, the aspect ratio of the sub-closed section c can be adjusted to 1 or less while reducing the weight.
Thereby, elastic buckling can be suppressed by shortening the elastic buckling period of the compression side wall part 11a (23a, 14a) accompanying the shortening of the vertical width, and the allowable limit load of the front side frame 2 can be increased. . Moreover, 0.05 ≦ t / b ≦ 0.12 where b is the separation width of the adjacent horizontal partition wall portions 11e (23e, 14e), and t is the plate thickness of the compression side wall portions 11a (23a, 14a). Since the plurality of horizontal partition walls 11e (23e, 14e) are formed so as to satisfy the relationship, occurrence of buckling in the elastic region of the frame material can be avoided.

A plurality of vertical partition walls 11b (23b, 14b) are formed in the main closed section C so as to be orthogonal to the longitudinal direction and are integrally formed with the compression side wall 11a (23a, 14a).
Thereby, since the upper end wall part 11c (23c, 14c) and the lower end wall part 11d (23d, 14d) are pulled by the plurality of vertical partition wall parts 11b (23b, 14b), the propagation from the compression side wall part 11a (23a, 14a) The deformation in the out-of-plane direction of the upper end wall part 11c (23c, 14c) and the lower end wall part 11d (23d, 14d) due to the elastic buckling wave can be suppressed.

  The first outer portion 11 (the third inner portion 23, the fourth outer portion 14) and the first inner portion 21 (the third outer portion 13, the fourth inner portion 24) are each made of a cast product. As described above, the structure including the plurality of horizontal partition wall portions 11e (23e, 14e) and the plurality of vertical partition wall portions 11b (23b, 14b) disposed in the main closed section C, which is difficult to be extruded, is simplified. It can be formed integrally with the compression side wall 11a (23a, 14a) by the method.

  A first bead portion 11f (second and third bead portions 23f, 14f) that is perpendicular to the longitudinal direction and recessed into the main closed section C side is formed in the compression side wall portion 11a (23a, 14a), and the vertical partition wall portion 11b (23b, 14b) is joined to the first bead portion 11f (second and third bead portions 23f, 14f), respectively. With this configuration, since the out-of-plane deformation of the upper end wall portion 11c (23c, 14c) and the lower end wall portion 11d (23d, 14d) can be suppressed, the front side frame 2 can be suppressed while suppressing a decrease in the allowable limit load of the front side frame 2. Can be bent and deformed starting from the position of the first bead portion 11f (second and third bead portions 23f, 14f). In addition, after the compression side wall portion 11a (23a, 14a) is buckled, the collapsed vertical partition wall portion 11b (23b, 14b) is formed between the compression side wall portion 11a (23a, 14a) and the tension side wall portion 21a (13a, 24a). Since the cross-sectional collapse of the position corresponding to the first bead portion 11f (second and third bead portions 23f, 14f) is suppressed, the EA efficiency can be increased.

Next, a modified example in which the embodiment is partially changed will be described.
1) In the above embodiment, an example of a front side frame has been described. However, a rear side frame, a suspension cross member, a bumper beam, a center pillar, an impact bar, or the like may be used for at least a vehicle frame on which a compressive load and a tensile load act. Any of them can be applied.

2] In the above-described embodiment, an example in which a non-heat treatment type 5000 series is used as the aluminum alloy material has been described. However, it is only necessary to have at least ductility and light weight, and the non-heat treatment type 1000 series, 3000 series, and 4000 series. The heat treatment type 2000 series, 6000 series, and 7000 series can be selectively employed according to the design requirements.
3] In the above embodiment, an example of two to four horizontal partition walls has been described from the viewpoint of EA efficiency. However, five or more horizontal partition walls may be employed from the viewpoint of design.

4) In the above embodiment, the examples of the two and three vertical partition walls have been described. However, it is only necessary to suppress at least the out-of-plane deformation of the upper end wall and the lower end wall corresponding to the bending deformation position, and the vicinity of the bending deformation position. One vertical partition wall may be provided. Further, four or more vertical partition walls may be provided in the vicinity of the bending deformation position. Moreover, it is also possible to provide a vertical partition wall near the folding deformation position without joining the vertical partition wall and the bead.

5] In the above embodiment, an example of a vehicle frame in which two outer bent portions and one inner bent portion are formed has been described, but the outer bent portion or the inner bent portion is at least one place. In addition, the number of the outer fold deformation portion and the inner fold deformation portion can be arbitrarily set.
6] In the above-described embodiment, an example in which a continuous U-shaped bead is used as the starting point of the bending deformation has been described, but a V-shaped bead or a bead divided into a plurality of parts may be used.
It may be at least a starting point of bending deformation, and the weak portion may be formed by surface treatment or the like.

7] In addition, those skilled in the art can implement the present invention with various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. is there.

V Vehicle 2 Front side frame 11 First outer portion 11a Compression side wall portion 11b Vertical partition wall portion 11e Horizontal partition wall portion 11f First bead portion 21 First inner portion 21b Engagement portion 21e Engagement rib 21f Engagement groove t (compression Side wall part) Thickness b (Horizontal partition wall part) Separation width H (engagement rib) Projection width

Claims (4)

A compression side portion including a longitudinal compression side wall portion on which a compressive load acts and a tension side portion including a longitudinal tension side wall portion on which a tensile load acts, and upper and lower ends of the compression side portion and the tension side portion In the aluminum alloy vehicle frame structure in which the cross-section perpendicular to the longitudinal direction and the main closed cross-section are substantially rectangular,
A plurality of horizontal partition walls extending from the compression side wall to the tension side wall and arranged to form a plurality of sub-closed cross sections adjacent to each other in the main closed cross section;
When the separation width of the adjacent horizontal partition wall parts is b, and the thickness of the compression side wall part is t,
0.06 ≦ t / b ≦ 0.12
The vehicle frame structure, wherein the plurality of horizontal partition walls are formed so as to satisfy the above relationship.   2. The vehicle according to claim 1, wherein one or a plurality of vertical partition walls are formed in the main closed section so as to be orthogonal to the longitudinal direction and integrally formed with the compression side wall. Frame structure.   The vehicle frame structure according to claim 2, wherein the compression side portion and the tension side portion are each made of a cast product. A bead that is perpendicular to the longitudinal direction and recessed into the main closed cross section is formed in the compression side wall,
The vehicle frame structure according to claim 2 or 3, wherein the vertical partition wall portion is joined to the bead.