JP6787365B2 - How to determine the shape and spot welding position of collision energy absorbing parts for automobiles - Google Patents

Description

The present invention relates to a method for determining the shape and spot welding position of an automobile collision energy absorbing component that buckles in the axial direction and absorbs collision energy when a collision is made from the front or the rear of a vehicle.

In order to ensure the safety of occupants in a vehicle such as a passenger car, there are front side members and rear side members as collision energy absorbing parts for automobiles that absorb collision energy.

In recent years, a high level of collision safety of automobiles has been required, and most of the collision energy absorbing parts for automobiles are manufactured using high-strength steel plates having a tensile strength of 440 to 780 MPa. Furthermore, with the spread of hybrid vehicles, it is expected that electric vehicles and fuel cell vehicles will spread rapidly in the future. Along with this, when installing large-capacity batteries and hydrogen tanks in vehicles, batteries and In order to protect the hydrogen tank, it is required for automobile collision energy absorbing parts such as front side members and rear side members to sufficiently absorb collision energy in a narrow space.

In addition, improving the fuel efficiency of automobiles is required not only to improve the value of automobiles but also to reduce carbon dioxide emissions as a measure against global warming, and further weight reduction of vehicles that directly leads to improvement of fuel efficiency is required. Weight reduction is also required for collision energy absorbing parts for automobiles.
In this way, it is important for the collision energy absorbing parts for automobiles to absorb the collision energy sufficiently and efficiently, and for that purpose, the collision energy absorbing parts for automobiles are stabilized by the collision load input in the axial direction. It is required to buckle in a bellows shape.

So far, a technique has been proposed in which buckling is stably generated when a collision load is input to a collision energy absorbing component for an automobile.

In Patent Document 1, a tubular second polygonal member is provided on the front side portion of the vehicle body reinforcing member extending in the front-rear direction of the vehicle body, and the collapse wavelength when the second polygonal member is crushed from the front end is λ. By setting the length of the second polygonal cross section that collapses to nλ / 2 (n = 1, 2, 3, ...), The second polygonal cross section is stably buckled, and the vehicle body A technique for preventing breakage of a reinforcing member and efficiently absorbing collision energy is disclosed. Here, it is said that the collapse wavelength λ in the technique can be determined not by trial and error but by analysis of the buckling waveform.
Further, in Patent Document 2, in a bumper stay formed with a closed cross section having a pair of facing flat surfaces, concave beads extending in a direction perpendicular to the vehicle front-rear axis are formed on the pair of flat surfaces by shifting each other. However, there is disclosed a technique for efficiently absorbing a collision load by crushing the concave bead in the axial direction starting from the concave bead at the time of a collision.

Japanese Unexamined Patent Publication No. 9-86438 JP-A-2009-45948

In the collision energy absorbing component for automobiles that buckles in the axial direction, if the buckling occurs after the start of buckling without being crushed in a bellows shape, the buckling position varies and stable energy absorption capacity cannot be obtained. In this regard, according to the techniques disclosed in Patent Document 1 and Patent Document 2 described above, it is possible to stabilize the buckling position and crush the shaft. However, in the technique according to Patent Document 1, it is necessary to perform buckling analysis in order to determine the shape for stable buckling deformation, and in the technique according to Patent Document 2, the bumper stay In the manufacturing process of the above, it is necessary to separately form a concave bead that is the starting point of buckling, and all the techniques require cost and time.

Further, as the above-mentioned reinforcing member and bumper stay for automobiles, a steel plate formed by spot-welding a cross-section hat-shaped member and a flat plate-shaped member, or spot-welding two cross-section hat-shaped members. When a tubular member made of wood is used, a crack is generated from spot welding in the vicinity of the buckling portion generated in the tubular member in the process of buckling by inputting a collision load to the tubular member, and this is the starting point. There was a case where a break occurred. Further, in the tubular member in which such fracture occurs, there is a problem that a high reaction force cannot be maintained in the process after the start of buckling, and the collision energy cannot be sufficiently absorbed.

The present invention has been made to solve the above-mentioned problems, and buckles stably in a bellows shape in the process after the start of buckling, and further, high collision without causing cracks around spot welding. It is an object of the present invention to provide a method for determining the shape and spot welding position of a collision energy absorbing component for an automobile having an energy absorbing ability.

In order to solve the above problems, the inventor causes a colliding body to collide with a tubular member having a cross-section hat-shaped member and a flat plate-shaped member, or a tubular member formed by spot welding two cross-section hat-shaped members against each other. A collision test was conducted to examine the effect of the shape and material properties of the tubular member on the buckling deformation of the tubular member. As a result, when the colliding bodies collide at a high speed of 10 m / s or more, the surface portion (top plate portion having a hat-shaped cross section) parallel to the abutting surface of the two steel plate members constituting the tubular member It was found that wavy deflection occurs and the wavy deflection becomes the starting point of buckling of the parallel surface portion, and further, the wavelength of the wavy deflection is substantially equal to the width of the surface portion parallel to the abutting surface. This phenomenon was characteristically generated when the collision was performed at a high speed, and was not observed when the collision test (crush test) was performed at a very low speed.

Further, in the process of buckling of the parallel surface portion due to the wavy deflection generated in the parallel surface portion, the parallel surface portion is convex to the vertical wall portion having a cross section hat shape which is a side surface at the axial position where the parallel surface portion is deformed in a concave shape. It has been found that the shape of the deformation occurs, and that cracks may occur around the spot weld near the position where the vertical wall portion is deformed in a convex shape, resulting in breakage.
The present invention has been made based on the above findings, and has the following configurations.

(1) In the method for determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the present invention, the flange is composed of a hat-shaped member having a top plate portion, a vertical wall portion and a flange portion, and a flat plate-shaped member. A tubular member that is spot-welded at a portion, and is arranged at the front or rear of the vehicle body. The shape and spot of an automobile collision energy absorbing component that buckles and absorbs collision energy when a collision load is input. In determining the welding position, the ratio between the axial length setting step for setting the axial length of the tubular member and the width of the top plate portion of the cross-sectional hat-shaped member is an integer. The first is a position at a distance of 3/4 or less of the width of the top plate determined from the tip of the tubular member in the step of determining the width of the top plate so as to be. A spot welding position determination step of determining a second and subsequent spot welding positions along the axial direction from the first spot welding position, with the determined top plate portion as the spot welding position and the spot welding interval. It is characterized by being equipped with.

(2) The method for determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the present invention is that two members having a top plate portion, a vertical wall portion and a flange portion and having a cross-sectional hat shape are spot welded at the flange portion. The shape and spot welding position of the collision energy absorbing parts for automobiles, which are tubular members that are arranged at the front or rear of the vehicle body and buckle when a collision load is input to absorb the collision energy. In determining, the ratio between the axial length setting step for setting the axial length of the tubular member and the width of the top plate portion of one of the two members is an integer. The top plate width determination step of determining the width of the top plate portion of the one member and determining the width of the top plate portion of the other member to be larger than that, and the tip of the tubular member. The position at a distance of 3/4 or less of the width of one of the top plates determined from the above is defined as the first spot welding position, and the width of the determined top plate is defined as the spot welding interval. It is characterized by including a spot welding position determining step of determining a second and subsequent spot welding positions from the spot welding position along the axial direction.

(3) In the above-mentioned (1) or (2), the spot welding position determining step is in the middle of the determined spot welding position, and the flange portion of the flange portion is located more than the spot welding position. It is characterized in that the position outside in the width direction is determined as an additional spot welding position.

In the present invention, a member having a cross-sectional hat shape and a flat plate-shaped member having a top plate portion, a vertical wall portion, and a flange portion, or two cross-sectional hat-shaped members are spot-welded at the flange portion. In a tubular member that is arranged at the front or rear of the vehicle body and buckles when a collision load is input to determine the shape and spot welding position of an automobile collision energy absorbing component that absorbs collision energy. The top plate is such that the ratio between the axial length setting step for setting the axial length of the tubular member and the width of the top plate portion of the cross-sectional hat-shaped member is an integer. The first spot welding position is a position at a distance of 3/4 or less of the width of the top plate determined from the tip of the tubular member and the step of determining the width of the top plate for determining the width of the portion. By providing a spot welding position determining step of determining the second and subsequent spot welding positions along the axial direction from the first spot welding position with the width of the top plate portion as the spot welding interval, the shape is tubular. A collision for automobiles so that the tubular member can be buckled in a bellows shape when a collision load is input in the axial direction of the member, and it is possible to prevent breakage of spot welding and efficiently absorb collision energy. The shape of the energy absorbing part and the spot welding position can be determined.

It is a figure which shows the flow of the process in the method of determining the shape and the spot welding position of the collision energy absorption component for automobiles which concerns on embodiment of this invention. It is a figure which shows an example of the tubular member which determined the shape and the spot welding position by the method of determining the shape and the spot welding position of the collision energy absorption component for automobiles which concerns on this embodiment. It is a figure which shows another example of the tubular member which determined the shape and the spot welding position by the method of determining the shape and the spot welding position of the collision energy absorption component for automobiles which concerns on this embodiment. It is a figure which shows the tubular member which made the 1st spot welding position d = D (= W1). It is a figure explaining the deformation in the axial position which the top plate part was deformed in an uneven shape by buckling, and the stress acting on a spot welding position (comparison). It is a figure explaining the deformation in the axial position which the top plate part was deformed in an uneven shape by buckling, and the stress acting on a spot welding position (the present invention). It is a figure explaining the generation position of the wavy deflection which occurs in the top plate part by the buckling of the tubular member which concerns on this embodiment. It is a figure explaining another aspect of the tubular member which concerns on this embodiment (the 1). It is a figure explaining another aspect of the tubular member which concerns on this embodiment (the 2). It is a graph which shows the measurement result of the load-stroke curve in the Example of this invention.

Prior to explaining the shape of the collision energy absorbing component for automobiles and the method for determining the spot welding position according to the present invention, the collision energy absorbing component for automobiles targeted by the present invention will be described. In the following description, those having the same function are designated by the same reference numerals, and duplicate description will be omitted.

The collision energy absorbing component for automobiles, which is the object of the present invention, is arranged at the front or rear of the vehicle body such as a front side member and a rear side member, and when a collision load is input, it buckles and crushes the shaft to generate collision energy. It absorbs and has a tubular member 1 exemplified in FIG. 2 and a tubular member 11 exemplified in FIG. 3 as its shape.

As shown in FIG. 2, the tubular member 1 has a cross-section hat-shaped member 3 having a top plate portion 3a, a vertical wall portion 3b, and a flange portion 3c, and a flat plate-shaped member 5 having a surface portion 5a and a side end portion 5b. Is spot-welded by butt-welding the flange portion 3c and the side end portion 5b, and the top plate portion 3a and the surface portion as a pair of parallel surface portions substantially parallel to the spot-welded flange portion 3c and the side end portion 5b. Has 5a and. As described above, in the tubular member 1, the width W1 of the top plate portion 3a is set to be equal to or less than the width W2 of the surface portion 5a. A member having a hat-shaped cross section is usually manufactured by press molding, and the width of the top plate portion is equal to or less than the width of the opening for the convenience of easily taking out the member from the press die after press molding. It becomes.

On the other hand, the tubular member 11 shown in FIG. 3 has a cross-sectional hat-shaped member 3 having a top plate portion 3a, a vertical wall portion 3b, and a flange portion 3c, and a top plate portion 13a, a vertical wall portion 13b, and a flange portion 13c. The member 13 having a hat-shaped cross section is spot-welded by abutting the flange portion 3c and the flange portion 13c, and is a top plate as a pair of parallel surface portions substantially parallel to the spot-welded flange portion 3c and the flange portion 13c. It has a portion 3a and a top plate portion 13a. Here, in the following description, it is assumed that the width W1 of the top plate portion 3a is narrower or equal to the width W2 of the top plate portion 13a as shown in FIG.

The dimensions (axial length L, etc.) of the tubular member 1 and the tubular member 11 are appropriately set according to the vehicle to be mounted. Further, as the material of the tubular member 1 and the tubular member 11, a metal plate such as a steel plate is used, and the member 3 and the member 13 having a hat-shaped cross section may be manufactured by, for example, press molding.

Next, a method for determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the embodiment of the present invention will be described.
As shown in FIG. 1, a method for determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the present embodiment includes an axial length setting step S1, a top plate width determining step S3, and spot welding. The position determination step S5 is provided. Hereinafter, unless otherwise specified, each of the above steps will be described with respect to the case of determining the shape and spot welding position of the tubular member 1 shown in FIG.

<Axial length setting process>
The axial length setting step S1 is a step of setting the axial length L of the tubular member 1.
The axial length L of the tubular member 1 may be appropriately set according to the vehicle to be mounted as a collision energy absorbing component for automobiles.

<Top plate width determination process>
In the top plate width determining step S3, the ratio (= L / W1) of the axial length L set in the axial length setting step S1 to the width W1 of the top plate portion 3a of the member 3 having the cross-sectional hat shape is an integer. This is a step of determining the width W1 of the top plate portion 3a so that (n = 1, 2, ...).

In the tubular member 1 in which the member 3 having a hat-shaped cross section and the flat member 5 are spot-welded, the width W1 of the top plate portion 3a is equal to or narrower than the width W2 of the surface portion 5a. Therefore, in the top plate portion width determining step S3, the width W1 of the top plate portion 3a is determined using the axial length L.

Further, as shown in FIG. 3, in the tubular member 11 in which the member 3 having a hat-shaped cross section and the member 13 are spot-welded, the top plate portion width determining step S3 is the axial length L of the tubular member 11. The ratio L / W1 of one member 3 to the width W1 of the top plate portion 3a of one of the ratios (L / W1, L / W2) of the width W1 and the width W2 of the top plate portion 3a and the top plate portion 13a, respectively. The width W1 is determined so as to be an integer, and the width W2 is determined so that the width W2 of the surface portion 5a of the other member 5 is larger than that (W2 ≧ W1).

<Spot welding position determination process>
In the spot welding position determination step S5, the position at a distance d of 3/4 or less of the width W1 of the determined top plate portion 3a from the axial tip of the tubular member 1 is set as the first spot welding position 7a, and the top plate is set. This is a step of determining the second and subsequent spot welding positions 7b along the axial direction from the first spot welding position 7a with the width W1 of the portion 3a as the spot welding interval D.

As shown in FIG. 2, the first spot welding position 7a may have a distance d from the tip of 3/4 or less of the width W1 (= spot welding interval D) of the top plate portion 3a, but is 1 of the width W1. It is preferably set to / 2. Further, since it is usually difficult to spot weld the starting end (d = 0) of the member, the distance d should be larger than 0.

The action and effect when a collision load is input to the collision energy absorbing component for automobiles whose shape and spot welding position are determined by the method of determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the present embodiment are shown in FIG. 4 and the tubular members 21 and 1 illustrated in FIG. 7 will be compared and described below.

Unlike the tubular member 1 described above, the tubular member 21 shown in FIG. 4 has a position at a distance D (= W1) exceeding 3/4 of the width W1 of the top plate portion 3a as a first spot welding position 23a. The width of the top plate portion 3a of the member 3 having a cross-section hat shape and the second spot welding position 23b on the flange portion 3c are determined, and the member 3 and the member 5 are spot welded at the spot welding positions 23 (23a, 23b). It was done.

At the moment when the colliding body collides with the axial tip of the tubular member 21 at a high speed of about 10 m / s or more, wavy deflection occurs in the top plate portion 3a and the surface portion 5a parallel to the flange portion 3c of the tubular member 21. , Unevenness occurs at the position where the deflection occurs. Then, at the moment when the reaction force from the tubular member 21 reaches the peak, buckling occurs at one or a plurality of ridges of the unevenness.

Here, since the width W1 of the top plate portion 3a of the tubular member 21 is determined so that the ratio L / W1 to the axial length L is an integer, the top plate portion 3a has a width W1. Wavy deflection with the same wavelength occurs. As a result, bellows-shaped buckling is stably generated in the top plate portion 3a when it collides with the tubular member 1.

Further, in the tubular member 21, spot welding positions 23 (23a, 23b) in the flange portion 3c are set in accordance with the position of the wavy deflection generated in the top plate portion 3a. Therefore, in the process of buckling and crushing the shaft after the collision, at the axial position 27 where the top plate portion 3a is deformed in a concave shape, the vertical wall portion 3b is deformed in a convex shape as shown in FIG. 5, and the flange portion 3c is deformed. Causes a deformation that is torn off. Therefore, tensile stress acts on the spot welding provided at the spot welding position 23 at the axial position 27.

Here, in spot welding of the tubular member 21 to which an ultra-high-strength steel plate having a tensile strength of more than 590 MPa is applied, a large difference in strength occurs between the nugget and the softened portion of the heat-affected zone (HAZ). As a result, when tensile stress is concentrated on this part, cracks occur, leading to breakage. Therefore, in the spot welding provided at the axial position 27 on which the tensile stress acts on the tubular member 21, cracks occur and the tubular member 21 is likely to break.

On the other hand, in the tubular member 1 shown in FIG. 7 in which the shape and the spot welding position are determined by the method according to the present embodiment, the width W1 of the top plate portion 3a is the axial length as in the tubular member 21. Since the ratio L / W1 to the L is determined to be an integer, the top plate portion 3a can be stably buckled in a bellows shape when a collision load is input. In addition to this, the position of the distance d from the tip in the axial direction is set as the first spot welding position 7a, and the interval equal to the wavelength of the wavy deflection generated in the top plate portion 3a is the spot welding interval D along the second and subsequent positions. By determining the spot welding position 7b, as shown in FIG. 6B, spot welding is not provided at the axial position 27 where the top plate portion 3a is deformed in a concave shape.

Therefore, in the tubular member 1 whose shape and spot welding position 7 are determined by the method according to the present embodiment, as shown in FIG. 7, the position in the axial direction is such that the flange portion 3c is peeled off. No spot welds are placed.
Further, at the axial position 25 where the top plate portion 3a is deformed in a convex shape, the vertical wall portion 3b is deformed in a concave shape as shown in FIG. 6A, and the flange portion 3c is deformed by pressing. As a result, a compressive stress acts on the spot weld provided at the spot weld position 7 at the axial position 25, but the spot weld is not broken by the compressive stress.
As a result, when a collision load is input in the axial direction, buckling deformation can be stably performed without causing cracks in spot welding.

Further, although the widths of the top plate portion 3a and the surface portion 5a of the tubular member 1 are different, in the present embodiment, the width W1 of the narrow top plate portion 3a is determined, and the determined width W1 is set to the spot welding interval D. The reason for this is as follows.

As described above, at the moment when the colliding body collides with the axial tip of the tubular member 1 at a high speed of about 10 m / s or more, unevenness is generated on the top plate portion 3a and the surface portion 5a, and the unevenness is generated at the wavy position. Deflection occurs. Then, at the moment when the reaction force from the tubular member 1 reaches its peak, buckling occurs from one or a plurality of uneven ridge lines generated on each of the top plate portion 3a and the surface portion 5a.

At this time, it is considered that the timing at which buckling occurs earlier in the top plate portion 3a, which is narrower than the surface portion 5a, because the wavelength of the wavy deflection generated by the collision of the colliding body is shorter. Therefore, even if both the top plate portion 3a and the surface portion 5a are buckled and deformed, the deformation caused by the buckling caused by the top plate portion 3a on the vertical wall portion 3b has a greater effect on the spot welding on the flange portion 3c. .. Therefore, by determining the spot welding position 7 in the flange portion 3c with reference to the width W1 of the top plate portion 3a, it is possible to prevent the spot welding from breaking due to deformation when the tubular member 1 buckles.

In this way, determining the spot welding position 7 with reference to the narrow top plate portion 3a is formed by spot welding the two cross-section hat-shaped members 3 and 13 as shown in FIG. The same applies to the tubular member 11. That is, in the tubular member 11, since the width W1 of the top plate portion 3a is narrower than the width W2 of the top plate portion 13a, the timing at which buckling starts earlier than that of the wide top plate portion 13a. The influence of buckling deformation of the top plate portion 3a on spot welding is greater. Therefore, even in the tubular member 11, the width W1 is determined for the narrow top plate portion 3a and the spot welding position is determined to prevent the spot welding from breaking due to deformation when the tubular member 11 buckles. can do.

However, in the above description, the width W1 of only the top plate portion 3a is determined so that the ratio to the axial length L is an integer, but the present invention has a width as compared with the top plate portion 3a. It is desirable to determine that the ratio L / W2 to the axial length L is also an integer for the surface portion 5a or the top plate portion 13a having a large size. As a result, it is expected that the bellows-like buckling deformation is likely to occur stably in the surface portion 5a and the top plate portion 13a, and the collision energy absorption capacity is improved.

Further, in the above description, the first spot welding position 7a and the second and subsequent spot welding positions 7b are determined along the axial direction in the flange portion 3c, but the shaft of the target tubular member 1 When the directional length L is short, there is a concern that the number of spot welding positions determined by the above method may be too small and the strength of the tubular member 1 and the tubular member 11 may be insufficient. ..

Therefore, as another aspect of the present embodiment, as shown in FIG. 8, the spot welding position determination step S5 is a member 33 having a cross-section hat shape having a top plate portion 33a, a vertical wall portion 33b, and a wide flange portion 33c. In the tubular member 31 formed by spot welding the flat plate-shaped member 35, the position outside the width direction of the flange portion 33c from the first and second and subsequent spot welding positions 7 is determined as an additional spot welding position 9. It may be something to do.

In the tubular member 31, by determining the additional spot welding position 9 outside the first and second spot welding positions 7 in the width direction, a part of the load at the time of collision is determined by the first and second spot welding positions. The spot welding is in charge of the above, and the tensile stress acting on the spot welding provided at the additional spot welding position due to buckling is reduced, and the spot welding can be prevented from breaking.

Further, in the wide flange portion 33c as shown in FIG. 8, an additional spot welding position 9 can be determined outside the spot welding position 7 in the width direction, and a cylinder provided with such a flange portion 33c. The shape member 31 may increase in weight. Therefore, as shown in FIG. 9, in the tubular member 41 in which the member 43 having a hat-shaped cross section and the flat member 45 are spot-welded, the flange portion 43c of the member 43 is projected outward in the width direction. Is provided, and the position of the protruding surface portion 43d is determined as the additional spot welding position 9. By determining the shape of the flange portion 43c in this way, it is possible to increase the number of spot welding points to secure strength while minimizing the weight increase, and to prevent breakage in spot welding during buckling. Can be done.

In the case of actually manufacturing a tubular member whose shape and spot welding position are determined by the method according to the present invention, the distance d from the axial tip of the first spot welding position and the spot welding interval. If it is within ± 10% with respect to D, even if the spot welding position deviates from the spot welding position determined by the distance d and the spot welding interval D, it is permissible and the effect of improving the collision energy absorption capacity is impaired. It's not a thing.

Further, in the case of a tubular member whose shape and spot welding position have been determined by the method according to the present invention, a flange portion for spot welding the two members together may be further bonded with an adhesive. As a result, it is possible to improve the collision energy absorption capacity and to provide an automobile collision energy absorption component having high rigidity.

An experiment was conducted to confirm the effect of the method for determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the present invention, and the results will be described below.

In this embodiment, the tubular member (shape A) of the hat-shaped member 3 and the flat plate-shaped member 5 shown in FIGS. 2, 4, and 7, and the tubular member 41 (shape B) shown in FIG. Was used as a test body, and a collision test was performed by colliding the colliding body with the axial tip of the test body to evaluate the collision energy absorption characteristics of each test body. Here, the test piece used for the collision test was made of steel plate (plate thickness 1.6 mm), and as shown in Table 1, steel plates having different material strengths were used.

In the collision test, a plate with a thickness of 10 mm is arc-welded to both ends (front end and rear end) in the axial direction of the test piece, one plate (rear end side) is fixed to the load load cell, and the other plate (tip side). On the other hand, a 250 kg colliding body was collided in the axial direction at an initial speed of 10 m / s. At this time, the initial kinetic energy of the colliding body is 12.5 kJ. Then, a load-stroke curve was created by measuring the load measured by the load load cell and the displacement stroke S of the colliding body. Further, from the created load-stroke curve, the peak value Fmax of the reaction force of the test piece, the collision energy absorption amount AE absorbed from the stroke to 100 mm, and the maximum stroke Smax required for the collision body to stop were obtained. ..

When a collision body is made to collide with the test body, the movement of the collision body is stopped when the collision energy absorption amount AE of the test body reaches the initial kinetic energy (= 12.5 kJ) of the collision body (kinetic energy is zero). The end point of the load-stroke curve corresponds to the maximum stroke Smax.
Table 2 shows the shape and spot welding position of the tubular member used as the test piece in the collision test.

In Table 1, in Invention Examples 1 to 3, the width of the top plate and the spot welding position are within the scope of the present invention according to the shape of the collision energy absorbing component for automobiles and the spot welding position determining method according to the present invention. It was decided to.

In Invention Example 1 and Invention Example 2, the tubular member 1 shown in FIG. 2 is used as a test body, and the width W1 of the top plate portion 3a is determined to be an integer at a ratio L / W1 = 6 to the axial length L. However, the spot welding position 7 is set to the spot welding interval D = W1. Further, in Invention Example 1 and Invention Example 2, the distance d from the tip of the first spot welding position 7a is set to 1/2 and 3/4 of the spot welding interval D, respectively.

In Invention Example 3, the tubular member 41 shown in FIG. 9 is used as a test body, and a protruding surface portion 43d is provided at a portion intermediate between the first and second spot welding positions 7 (7a, 7b) and added to the protruding surface portion 43d. The spot welding position 9 of the above is provided, and the member 43 and the member 45 are spot welded. The width W1 of the top plate portion 43a in Invention Example 3 and the first and second spot welding positions 7 (spot welding interval D, distance d) were set to the same conditions as in Invention Example 1.

On the other hand, in Comparative Examples 1 to 3 shown in Table 1, the width W1 of the top plate portion 3a and the spot welding position 7 are outside the scope of the present invention. That is, in Comparative Example 1, the ratio L / W1 = 4.7 of the axial length L and the width W1 is not an integer, and in Comparative Example 2, the spot welding interval D is set to 3 / of the width W1 of the top plate portion 3a. In Comparative Example 3 where 2 is set, the distance d from the tip of the first spot welding position 7a is set to d = D larger than 3/4D.

As a typical load-stroke curve obtained by performing a collision test, FIG. 10 shows the results of Comparative Example 3 and Invention Example 1. Note that FIG. 10 uses a steel plate having the material symbol 980 shown in Table 1.

As shown in FIG. 10, in both Comparative Example 3 and Invention Example 1, the reaction force rapidly increased immediately after the colliding body collided with the plate at the tip of the test body and showed a peak value (Fmax), and then the buckling. The bending has started and the reaction force has plummeted.

Here, in Comparative Example 3, a crack occurs in the spot welding of the flange portion 3c at the axial position where the vertical wall portion 3b is deformed in a convex shape due to the buckling of the top plate portion 3a, and the steel plate is formed as the buckling progresses. Progressed to breakage. Due to this fracture, the reaction force after the start of buckling was lower than that of Invention Example 1, and the amount of collision energy absorbed expected from the material strength of the steel sheet could not be obtained.

On the other hand, in Invention Example 1, since there is no spot welding in the vicinity of the axial position where the vertical wall portion 3b is deformed convexly due to buckling, cracks do not occur, and the steel plate does not break and accompanies compression. Buckling was stable and repeated. As a result, as compared with Comparative Example 1 in which fracture occurred, the result was obtained that the amount of collision energy absorbed was increased with a shorter stroke.

Table 3 summarizes the test results of the collision energy absorption characteristics of Invention Examples 1 to 3 and Comparative Examples 1 to 3.

From Table 3, in both the invention example and the comparative example, the reaction force increased as the steel sheet strength increased, and the collision energy absorption amount AE improved accordingly, and the maximum stroke Smax became smaller.
However, in Comparative Examples 1 to 3, the result was that fracture occurred in the process of buckling progressing. On the other hand, in Invention Examples 1 to 3 and Comparative Examples 1 to 3, the collision energy absorption amount AE is large and the maximum stroke Smax is also small without breaking in the process of buckling progressing. As a result, the collision energy absorption characteristics are improved.

In particular, Invention Example 3 using the tubular member 41 as a test body sets an additional spot welding position 9 at an intermediate position of the spot welding position 7 in the tubular member 1 according to Invention Example 1 and Invention Example 2. However, the tubular member 41 has a protruding surface portion 43d in which the flange portion 43c protrudes outward at an axial position in which the vertical wall portion 43b is deformed convexly due to buckling, and spot welding of the protruding surface portion 43d is performed on the vertical wall portion. Since it is separated from the hem of 43b, it was confirmed that no cracks were generated around the spot weld and no breakage occurred.

From the above, by determining the shape and spot welding position of the collision energy absorbing component for automobiles according to the present invention, it is possible to prevent cracks from occurring in the spot welding around the buckled portion when a collision occurs at high speed. It has been shown that it is possible to provide collision energy absorbing parts for automobiles that are stable and have high energy absorbing capacity.

1 Cylindrical member 3 Cross-section hat-shaped member 3a Top plate part 3b Vertical wall part 3c Flange part 5 Flat plate-shaped member 5a Surface part 5b Side end part 7 Spot welding position 7a First spot welding position 7b Second spot welding position 9 Additional spot welding position 11 Cylindrical member 13 Cross-section hat-shaped member 13a Top plate portion 13b Vertical wall portion 13c Flange portion 21 Cylindrical member 23 Spot welding position 23a First spot welding position 23b Second spot welding position 25 Axial position that deforms convexly 27 Axial position that deforms concave 31 Cylindrical member 33 Cross-section hat-shaped member 33a Top plate 33b Vertical wall 33c Flange 41 Cylindrical member 43 Cross-section hat-shaped member 43a Top plate Part 43b Vertical wall part 43c Flange part 43d Protruding surface part 45 Flat plate-shaped member 45a Surface part 45b Side end

Claims (3)

A tubular member in which a hat-shaped member having a top plate portion, a vertical wall portion, and a flange portion and a flat plate-shaped member are spot-welded at the flange portion, and are arranged at the front or rear portion of the vehicle body. In the method of determining the shape and spot welding position of the collision energy absorbing parts for automobiles that buckle and absorb the collision energy when the collision load is input.
Axial length setting step for setting the axial length of the tubular member, and
A top plate width determination step of determining the width of the top plate so that the ratio of the axial length to the width of the top plate of the member having the cross-sectional hat shape is an integer.
The position at a distance of 3/4 or less of the width of the top plate portion determined from the tip of the tubular member is defined as the first spot welding position, and the width of the determined top plate portion is defined as the spot welding interval. The shape and spot welding position of the collision energy absorbing component for automobiles, which comprises a spot welding position determining step of determining the second and subsequent spot welding positions along the axial direction from the spot welding position of 1. How to decide. A tubular member in which two hat-shaped members having a top plate portion, a vertical wall portion, and a flange portion are spot-welded at the flange portion, and are arranged at the front or rear portion of the vehicle body to apply a collision load. In the method of determining the shape of the collision energy absorbing part for automobiles that buckles and absorbs the collision energy when input and the position of spot welding,
Axial length setting step for setting the axial length of the tubular member, and
The width of the top plate portion of one member is determined so that the ratio of the axial length to the width of the top plate portion of one of the two members is an integer, and the top plate portion of the other member is determined. The top plate width determination process that determines the width of the top plate to be larger than that,
The position at a distance of 3/4 or less of the width of one of the top plates determined above from the tip of the tubular member is set as the first spot welding position, and the width of one of the determined top plates is the spot welding interval. As a result, the shape of the collision energy absorbing component for automobiles is characterized by comprising a spot welding position determining step of determining a second and subsequent spot welding positions from the first spot welding position along the axial direction. How to determine the spot welding position. The spot welding position determining step is characterized in that a position intermediate between the determined spot welding positions and outside the width direction of the flange portion from the spot welding position is determined as an additional spot welding position. The method for determining the shape and spot welding position of an automobile collision energy absorbing component according to any one of claims 1 or 2.