JPH10316024A - Vehicle body structural member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automotive structural member for vehicle body which can reduce total weight by having proof stress required at the time of high-speed driving and a proof stress difference required at the time of low-speed driving. SOLUTION: This is a structural member mounted on a body of an automobile where collision load is sometimes applied to its one end 12. This structural member 10 consists of a first member 14 which is disposed to a prescribed range from one end and is formed into a prescribed cross-section shape by bending a sheet material, and a second member 16 connected to the first member also formed into the prescribed cross-section shape by bending the sheet material. The sheet material of the first member is set so that the ratio of a yield point to strain rate may be larger than that of the second member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structural member for a vehicle body of an automobile, and more particularly to a structural member suitable for a front side member or a rear side member of an automobile installed in a place where a collision load may be received.

[0002]

2. Description of the Related Art In some cases, a structural member installed at a place where it may receive a collision load is capable of deforming and absorbing collision energy. The structural member has an impacted portion to which an impact load is applied, and a maintenance portion connected to the impacted portion. The structural member has, for example, the maintenance portion mainly having a strength capable of protecting the cabin when a collision load is applied at a high speed traveling of 50 km / h or more.For example, the collision load is applied at a low speed traveling of 15 km / h or less. Then, in order to minimize the damage range of the vehicle body, it is preferable that the maintenance part and the collision part have a difference in proof stress that can be sequentially collapsed from the collision part.
Therefore, the structural member may be formed with a predetermined thickness such that the thickness of the plate forming the maintenance portion is greater than the thickness of the plate forming the impacted portion. One example is a structural member for an automobile (Japanese Utility Model Laid-Open No. 61-67281) in which a continuous steel plate obtained by butt welding the above steel plates is bent into a predetermined shape.

[0003]

Steel sheets are generally used as structural members of automobiles. FIG. 4 shows the relationship between the strain rate and the yield point qualitatively. Normal,
Since the maintenance portion and the impacted portion are formed by steel plates having different thicknesses but having the same content components, the steel plate A for the maintenance portion and the steel plate B for the impacted portion have the same tendency. Now, it is assumed that the vehicle speed is substantially proportional to the strain rate of the steel sheet, the proof stress of the steel sheet is substantially proportional to the yield point, and the proof stress required for the maintenance part A is F.
It is assumed that a required proof stress difference between the object and the colliding portion B is f.

[0004] The thickness of each of the maintenance portion and the impacted portion is determined as follows. Since is a state of collapsed strength F at the impacted portions required for the maintenance part high speeds when V _h, thickness having a strength of yield strength F or the proof stress smaller than the high-speed traveling at V _h approximates to Is used for the portion B to be hit. Then, determine the thickness of the maintenance portion A so as to ensure the strength difference f that is required between the maintenance portion and the impacted portion to the low speed during running V _l. As a result, the actual yield strength with the structural member at a high speed during running V _h is a considerable distance value from (F + f), and the necessary strength F. This is unfavorable both in terms of weight and material economy.

The present invention provides a structural member for a vehicle body of an automobile which has a proof stress required at a high speed running and a proof stress difference required at a low speed running and can reduce the overall weight or can be manufactured at low cost. I will provide a.

[0006]

SUMMARY OF THE INVENTION The present invention is a structural member installed on the body of an automobile, in which a collision load may be applied to one end. The structural member is disposed within a predetermined range from the one end, a first member formed by bending a plate material to have a predetermined cross-sectional shape, and formed by bending a plate material to have a predetermined cross-sectional shape, And a second member connected to the first member. The plate of the first member is determined so that the ratio of the yield point to the strain rate is larger than that of the plate of the second member.

[0007]

[Operation and Effect] The plate material of each of the first member and the second member is determined. In this case, two plate members of the same type but different in component content are selected, or two plate members of different types are selected. When the strength of the first member and the thickness of the first member having a strength smaller than or similar to the strength required at the time of high-speed running and the strength are determined, the strength of the first member at the time of low-speed running is determined. In order to ensure the required strength difference between the first member and the second member, in other words, the plate member of the second member so as to have a strength obtained by adding the strength difference to the strength at the time of low-speed running, Determine its thickness.

Since the ratio of the yield point to the strain rate of the plate member of the first member is larger than that of the plate member of the second member, the yield strength of the plate member of the first member at low speed traveling is the same as that of the yield point to the strain speed. It is lower than the proof stress at low speed running in some cases. Therefore, the second obtained by adding a difference in proof stress to this low proof stress.
Since the proof stress of the plate member of the member is also reduced, the thickness of the plate member of the second member can be reduced to reduce the overall weight. Further, the plate material of the second member can be changed to a lightweight and inexpensive one.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A structural member installed on a vehicle body is a front side member or a rear side member in which a collision load may be applied to one end. The structural member includes a first member disposed within a predetermined range from the one end, and a second member connected to the first member. The first member and the second member can be sequentially crushed from the one end, for example, when a collision load is applied at a low speed of 15 km / h or less to reduce the damage range of the vehicle body as much as possible. The second member has a strength that can protect the cabin when a collision load is applied during high-speed running of, for example, 50 km / h or more. The first member and the second member have substantially the same cross-sectional shape. The first member and the second member overlap one connecting portion to be connected to the other connecting portion, and are connected by welding such as mash seam welding or laser welding, or by tightening or riveting a bolt and a nut. Can be connected by tightening.

[0010] The plate member of the first member is determined such that the ratio of the yield point to the strain rate is larger than that of the plate member of the second member. For example, SPC is used as the plate material of the first member.
270 can be used as the plate member of the second member. This is a combination of plate materials of the same type but containing different components, but different types of plate materials can also be combined.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A structural member 10 installed on a vehicle body is
A collision load may be applied to one end 12,
It comprises a first member 14 and a second member 16. In the embodiment shown, the structural member 10 is a front side member,
It is arranged in the front-rear direction of the vehicle body and extends from the engine room of the automobile to the rear compartment.

The first member 14 is formed by bending a plate material to have a predetermined cross-sectional shape, and is arranged from one end 12 to a predetermined range. Here, the predetermined cross-sectional shape is a shape required for a structural member. In the illustrated embodiment, the first member 14 has a rectangular cross-sectional shape cut along a virtual vertical plane perpendicular to the center axis of the vehicle body. It is formed so that it becomes. The predetermined range is, for example, a range that can be sequentially crushed from one end 12 when a collision load is applied at a low speed of 15 km / h. As in the illustrated embodiment,
When the structural member 10 is a front side member, since the deformation of the front side member is restricted by the engine and the transmission 18, the first member 14 only needs to extend to the front end of the engine and the transmission 18.

The second member 16 is formed by bending a plate material into a predetermined sectional shape, that is, a sectional shape substantially the same as the sectional shape of the first member 14, and is connected to the first member 14. In the embodiment shown, the rear end 15 of the first member 14
Into the front end of the second member 16 and overlap,
They are connected by welding.

The plate of the first member 14 is determined so that the ratio of the yield point to the strain rate is larger than that of the plate of the second member 16. In the illustrated embodiment, the first member 14 is a plate of SPC270 and has a thickness of 1.4 mm. The second member 16 is a plate of SPC440 and has a thickness of
1.6 mm. As shown in FIG. 3, the slope of the characteristic C of the SPC 270 is steeper than that of the characteristic D of the SPC 440. Since the ratio is a gradient, that is, a proportional constant in the graph of FIG. 3, SPC 270 and SPC 440 satisfy the above condition.

Now, the proof stress F required in the high speed running range H is set to, for example, about 50 kgf / cm ² , and the proof stress F required in the low speed running range L is set to, for example, 20 kgf / cm 2.
^It shall be set to about ² . Then, SPC270
Has a proof stress less than the proof stress F in the high-speed range but approximates the proof stress F, and thus has the quality as the first member. Therefore, the SPC 270 can be adopted as the first member 14. The boundary value of the SPC 270 in the low-speed running range is 23 kgf / cm ² . On the other hand, the boundary value of the SPC 440 in the low-speed running range is 44 kgf / cm ² , which satisfies the proof stress difference. Since the boundary value of the SPC 440 in the high-speed running range is 58 kgf / cm ² , the proof stress F
Is exceeded. Therefore, the SPC 440 can be adopted as the second member 16.

When a collision load is applied to the end portion 12 of the structural member 10 during low-speed traveling, as shown in FIG.
Are sequentially crushed from the end 12 to absorb the collision energy.
When a collision load is applied during high-speed running, the first member 14 is crushed, and at the same time, the second member 16 is deformed and absorbs collision energy. At this time, the engine and transmission 1
8 is displaced rearward without being deformed. As a result, a space that is not collapsed remains in the range of S, and the cabin can be protected.

A shown in FIG. 4 is a plate of SPC440 having a thickness of 1.8 mm, and B is a plate of SPC440 having a thickness of 1.4 mm. Therefore, according to the embodiment shown in FIG. 3, D, that is, a plate material of SPC440 having a thickness of 1.6 mm
As a result of adopting the member 16, weight reduction was achieved.

[Brief description of the drawings]

FIG. 1 is a side view of an embodiment of a vehicle body structural member according to the present invention, showing a state before deformation.

FIG. 2 is a side view showing a state after deformation of the vehicle body structural member shown in FIG. 1;

FIG. 3 is a graph showing a relationship between a strain rate and a yield point of two plates used for a structural member for an automobile body according to the present invention.

FIG. 4 is a graph qualitatively showing a relationship between a strain rate and a yield point of a plate material used for a vehicle body structural member according to the present invention and a conventional vehicle body structural member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Structural member 12 End part 14 1st member 16 2nd member

Claims (1)

[Claims] 1. A structural member installed on a vehicle body of a vehicle, in which a collision load may be applied to one end portion, wherein a plate material is disposed within a predetermined range from the one end portion by bending a plate material. A first member formed in a predetermined sectional shape;
The plate material is bent to form a predetermined cross-sectional shape, and the first
A structural member for a vehicle body of an automobile, comprising a second member connected to a member, wherein the plate member of the first member is determined such that a ratio of a yield point to a strain rate is larger than that of the plate member of the second member.