JP2003225714A - Method for forming metallic tube and member for absorbing collision energy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a metallic tube in which one kind of a pressing tool deals with tubes of various sizes in the outside diameter and by which the metallic tube is formed into the target special cross-sectional shape by once pressing and also a member for absorbing collision energy obtained by using a special shaped tube manufactured by the forming method. <P>SOLUTION: (1) In this method for forming the metallic tube, a pair of comb press fixtures 4, 4a with which, preferably, a cavity 7 having a cross section of rotationally symmetrical shape is formed by fitting the teeth 5, 5a of a comb into the clearances 6a, 6 of a comb of a partner is used, the metallic tube 3 is put in the cavity 7 and the metallic tube 3 is compressed and formed by reducing the cavity with a uniaxial press 8. It is preferable that the width of the teeth of the comb is 1-30% of the outside diameter of the metallic tube before compress-forming. (2) This member for absorbing the collision energy is obtained by using the special shaped tube formed by the method (1) in which a steel tube the ratio of the thickness to the outside diameter of which is 0.2-5% is put in the cavity and the special shaped tube is formed by compression- forming with the compression ratio of the outside diameter of 20-70%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a metal tube and a collision energy absorbing member, and more particularly, to a method of forming a metal tube capable of advantageously manufacturing a profiled tube and a profiled tube manufactured by the method. The present invention relates to a collision energy absorbing member.

[0002]

2. Description of the Related Art A front side member, a rear side member, and the like, which constitute a vehicle, play an important role as a collision energy absorbing member that is appropriately crushed during a vehicle collision to absorb energy at the time of collision and suppress deformation of a cabin. ing. FIG. 7 shows an example of the front side member 20 directly connected to the bumper 21 of the automobile. For example, due to a collision from the front, the collision load 22 is transmitted from the bumper 21 in the axial direction of the front side member 20. Due to this load load, the front side member 20 is crushed in a bellows shape and absorbs collision energy when crushed.

In order to improve the safety in the event of a vehicle collision, a collision energy absorbing member such as a front side member is required to have a high energy absorbing ability. In order to meet such a demand, for example, in Japanese Unexamined Patent Publication No. 4-310477, a basic member extruded into a closed cross-section structure by a light metal and a basic member fitted into the basic member and having substantially the same length are compressed at least at the tip. A side member of a vehicle has been proposed in which a double structure is formed with a reinforcing member provided with a deformation promoting portion, preferably a notch. According to the side member disclosed in Japanese Patent Laid-Open No. 4-310477, bending rigidity, torsional rigidity, and crushing deformation can satisfy characteristics equal to or higher than those of the steel side member. However, the side member described in Japanese Patent Application Laid-Open No. 4-310477 has a problem that the basic member is an extruded material made of light metal and is expensive, and the structure of the reinforcing member is complicated, so that the manufacturing cost is high. It was

Further, in Japanese Patent Laid-Open No. 11-208519, a member which absorbs a shock at the time of collision by plastic deformation in the axial direction is formed of a hollow material, and the hollow material is provided on a surface passing through the central axis of the hollow material. There has been proposed an automobile body frame structure formed of a light metal material, which is characterized in that a rib contacting the inner surface of the vehicle is provided. The vehicle body frame structure described in Japanese Patent Laid-Open No. 11-208519 uses a light metal material and is preferably manufactured by extrusion molding, and is said to have excellent impact energy absorption characteristics at the time of collision. However, there is a problem that an extrusion molding material of a light metal material such as aluminum is expensive. In addition, when a light metal material is used for the collision energy absorbing member, there is also a problem in that it is restricted in joining with a member made of an adjacent steel plate.

Further, in Japanese Patent Laid-Open No. 2000-254997, a sheet molding compound molded product obtained by mixing an epoxy acrylate resin and a polyisocyanate compound in appropriate amounts is combined with a steel material, preferably with a hat-shaped cross section. The impact energy absorbing member has been proposed. The impact energy absorbing member described in Japanese Patent Laid-Open No. 2000-254997 is lightweight, and has the maximum load during compression deformation,
The average load can be easily adjusted by combining steel materials and sheet molding compound molded products. However, this member has a problem that the manufacturing cost is high because it requires steps such as forming a sheet molding compound molded product and joining a steel material and the sheet molding compound molded product.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned problems of the prior art and are lightweight, excellent in productivity, high in deformation energy at the time of compression deformation, and inexpensive, collision energy for automobiles. For the purpose of providing an absorbing member, for example, as shown in FIG. 6, an inner tube 1 made of a metal tube having an irregular shape with an uneven cross section is formed from a metal tube having a circular or polygonal cross section. Outer tube 2
In addition, Japanese Patent Application No. 2001-334024 proposes a collision energy absorbing member having a double pipe structure which is inserted such that the inner surface of the outer pipe 2 and the maximum diameter portion 11 of the inner pipe 1 are in contact with each other. According to this, it is possible to manufacture an automobile member having an excellent collision energy absorbing ability at a lower cost and with a higher productivity than the conventional techniques described in the above publications.

By the way, in the above-mentioned Japanese Patent Application 2001-334024,
The well-known roll forming method was used to manufacture the deformed pipe (: a pipe having a deformed cross-sectional shape) used as the inner pipe of the double pipe structure. This is a method of reshaping circular pipes in stages with multiple stages of rolls in a stepwise manner, and it is possible to perform continuous molding connected to the outlet side of the electric resistance welded pipe manufacturing process. is there.

However, in the roll forming method, although productivity is good, a large number of roll stands are required for reshaping, and a dedicated roll group is required for each outer diameter of the pipe. However, there is a drawback that the equipment becomes large-scale. In addition, this method
It has the drawback of not being suitable for small-volume production. Therefore, the present invention provides a method for forming a metal pipe that does not have these drawbacks.
A metal pipe forming method capable of handling various pipe outer diameter sizes with various types of pressing tools and forming a target deformed cross-sectional shape with one pressing is performed by collision using the deformed pipe manufactured by the forming method. It is intended to be provided together with an energy absorbing member.

[0009]

Means for Solving the Problems The present invention (1), which has achieved the above-mentioned object, uses a pair of comb-type press jigs in which comb teeth are fitted into a mating gap of a mating member to form a cavity. A metal tube is inserted into the metal tube, and the cavity is reduced in diameter by a uniaxial press to compression-mold the metal tube. The present invention
In (1), it is preferable that the cavity has a rotationally symmetrical cross-section, and that the width of the comb teeth is 1 to 30% of the outer diameter of the metal tube before compression molding.

Further, in the present invention (2), the metal pipe to be inserted into the cavity is a steel pipe having a wall thickness to outer diameter ratio of 0.2 to 5%, and the outer diameter compression rate in compression molding is 20 to 70%. A collision energy absorbing member using a deformed pipe formed by the present invention (1).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a three-dimensional schematic view illustrating an embodiment of the present invention (1). In the present invention (1), FIG.
As shown in FIG. 5, a pair of comb-type press jigs 4 and 4 a whose comb teeth 5 and 5 a are fitted in the mating gaps 6 a and 6 to form the cavity 7 are used to insert the metal tube 3 into the cavity 7. , The cavity 7 as shown in FIG. 1 (b).
Is reduced by a uniaxial press 8 to compression-mold the metal tube 3. 1 (c) and 1 (d) show a state in which the upper comb-type press jig 4 in FIGS. 1 (a) and 1 (b) is removed.

According to the present invention (1), the pipe is buckled by receiving the compressive force, and the cross-sectional shape becomes uneven so that the pipe is deformed. As the compression progresses, the cross section of the tube inner space shrinks, and accordingly, the cross-sectional shape of the tube changes so as to bend toward the tube center side. Therefore, the cross-sectional shape varies depending on the degree of compression of the tube and is not uniform.
Therefore, in FIGS. 1 (b) and 1 (d) in which the degree of compression is not specified, the cross-sectional shape of the metal tube 3 is indicated by "?".

As is apparent from this configuration, the present invention (1)
According to this, the original pipe (the pipe before being compressed) that can enter the cavity 7 can be deformed by one type of pressing tool including the pair of press jigs 4 and 4a regardless of the outer diameter size. Further, by changing the degree of tube compression by reducing the diameter of the cavity 7 with one pressing by the uniaxial press 8, it is possible to manufacture deformed tubes having various cross-sectional shapes corresponding to the degree of compression.

On the other hand, it is preferable that the deformed tube as the collision energy absorbing member has a smaller strength anisotropy in the circumferential direction of the tube from the viewpoint of versatility, and for that reason, it is preferable that the sectional shape has rotational symmetry. In order to manufacture a deformed pipe whose cross-sectional shape has rotational symmetry according to the present invention (1),
It is preferable that the cavity has a rotationally symmetrical cross section. Also,
Of course, it is preferable that the rotationally symmetrical shape of the cross section is preserved even when the cavity is reduced. As a result, during the tube compression process, the cross-sectional contour of the tube has a rotationally symmetrical shape following the inner surface of the cavity. FIG. 1 shows, as an example, the case where the cavity has a square cross section that is a four-fold rotational symmetry. The original tube is a tube with a regular polygonal section (regular polygonal tube) or a tube with a circular section, in which the cross-sectional deformation at the initial stage of tube compression is isotropic due to the cross-sectional similarity reduction of a rotationally symmetrical cavity. (Cylindrical tube) is preferable, but the most inexpensive and easily available circular tube is preferable.

FIG. 2 is a schematic sectional view showing an example of the process of deforming a metal tube according to the present invention (1). In this example, the metal is steel, the raw pipe is a circular pipe, and the hollow cross-sectional shape is square. In addition,
In the present invention, the degree of compression is expressed by the formula: γ = √ {(cavity cross-sectional area when the tube compression is in progress) / (cavity cross-sectional area when the original pipe is in contact)} (× 10
It is represented by the outer diameter compressibility γ defined by 0%). The outer diameter compression rate γ is equal to the cavity diameter reduction rate based on the cavity diameter at the time of contact with the original pipe.

In FIG. 2, as the γ increases from 0% to 57%, the cross-sectional shape of the pipe is circular (a: γ = 0%) → concave square (b: γ = 19%) → four of the original pipe. Star shape (c: γ = 28.5%) → Four-pointed star with bulging convex parts (d: γ = 38%) → Isolated four-leaf shape (e: γ) where the four concave parts are in contact with each other and the four convex parts are separated = 47.5%) → Concentrated four-lobed shape with four concave portions in contact with each other and four convex portions in contact with each other (f: γ =
57%) and so on. The cross-sectional rigidity of the deformed pipe increases in this order. Furthermore, if γ exceeds 70%, it is difficult to preserve the 4-fold rotational symmetry of the cross-sectional shape of the pipe, and the shape tends to be distorted.

Further, in the present invention (1), the width of the comb teeth of the comb-type press jig (: the dimension in the direction in which the comb teeth are aligned) is set to 1 to the outer diameter of the raw pipe.
30% is preferable. The width of the comb teeth is 1% of the outer diameter of the original pipe
If the width is less than 30% of the outer diameter of the original pipe, the constraint pitch of the pipe becomes too coarse and press molding is performed. This is because the sex deteriorates.

Next, according to the present invention (2), the metal pipe is a steel pipe, the ratio of the wall thickness of the raw pipe to the outer diameter is 0.2 to 5%, and the outer diameter compressibility is 20 to 70.
%, Which is a collision energy absorbing member using a deformed pipe formed by the present invention (1). The structure of the collision energy absorbing member of the present invention (2) is a double pipe structure as shown in FIG.
Either (a) or the single-tube structure (b) may be used. In the double pipe structure, for example, as the inner pipe 1 to be inserted into the prismatic outer pipe 2, and in the single pipe structure, the deformed pipe molded in the present invention (1) is used. Either structure can have sufficient ability to absorb collision energy.

In the present invention (2), in forming and manufacturing the deformed pipe to be used in the present invention (1), the metal pipe is a steel pipe,
The ratio of the wall thickness of the raw pipe to the outer diameter was 0.2 to 5%, and the outer diameter compression ratio in compression molding was 20 to 70%. The reason is as follows.・ The point that the metal pipe is a steel pipe: If it is a steel pipe, the original pipe can be obtained at a lower cost than other metal pipes (copper pipe, aluminum pipe, etc.), and it has excellent rigidity after compression molding. -The ratio of the wall thickness of the raw pipe to the outer diameter is set to 0.2 to 5%: If this ratio is less than 0.2%, it is difficult to secure the cross-sectional rigidity of the deformed pipe, and it is difficult to manufacture the raw pipe and the manufacturing cost increases. On the other hand, with a thick material whose ratio exceeds 5%, it is difficult to perform compression molding with a comb-type press jig, and the weight becomes too large to be applied to a collision energy absorbing member for automobiles.・ Outer diameter compressibility γ set to 20-70%: When γ is less than 20%, the increase in collision energy absorption capacity due to the deformation of the pipe cross section in the single pipe structure is small. On the other hand, if γ exceeds 70%, the uniaxial press load will increase extremely, and a large-scale press machine will be required. It becomes unsuitable as a collision energy absorbing member.

[0020]

EXAMPLE A circular tube made of steel equivalent to JIS STKM13B by the method shown in FIG. 1 using the comb-shaped press jig 4 in which the width of comb teeth 5 and 5a is 30 mm and the cross-sectional shape of cavity 7 is square in FIG. The tube formed by compression molding under each condition shown in Table 1 (condition A
Then, a member having a single pipe structure (conditions A to F) or a double pipe structure (conditions G to J) was manufactured using the original pipe without compression molding. In the double-tube structural member, the deformed pipe formed by compression molding was used as the inner pipe, and the square pipe of the same steel type as the inner pipe (wall thickness = 1.2 mm) was used as the outer pipe. The outer diameter of the original pipe of the deformed pipe used as the inner pipe of the double pipe structure member is such that the cross-sectional area of the double pipe structure member, that is, the area occupied by the material in the cross section is the same as that of the single pipe structure member (about 670 mm ² ). They were selected so that the weights of the members were equal.

[0021]

[Table 1]

The following tests were conducted on these members. (Test 1: End face collision test) One end in the longitudinal direction of the member is supported and a weight of 100 kg is made to collide with the other end face at a speed of 50 km / h and 100 m
The absorbed energy at the time of m deformation was obtained by integrating the displacement-load curve obtained at the time of collision deformation. The results are summarized in FIG. In addition, in FIG. 4, the absorbed energy is shown as an index (: ratio to the single circular tube member). Figure 4
Therefore, in the case of a member using a deformed pipe compression-molded with an outer diameter compression rate of 20% or more (: Example of the present invention (2)), the absorbed energy increased remarkably as the outer diameter compression rate increased and reached a high level. I know you will reach.

(Test 2: Side collision test) The members are supported at two locations in the longitudinal direction (interval of 500 mm), and a weight of 100 kg is collided at the center of the two locations at a speed of 50 km / h at right angles to the longitudinal direction of the members. , The absorbed energy in the entire deformation area is obtained by integrating the displacement-load curve obtained during collision deformation, and the bending maximum load, which is the maximum load during deformation, is calculated from the displacement-load curve. I asked. The results are summarized in FIG. In addition, in FIG. 5, the maximum bending load × absorbed energy is shown as an index (: ratio with a single circular pipe member). Figure 5
Therefore, in the case of a member using a deformed pipe compression-molded with an outer diameter compression ratio of 20% or more (: Example of the present invention (2)), the maximum bending load x
It can be seen that the absorbed energy increases remarkably as the outer diameter compressibility increases and reaches a high level.

As described above, the collision energy absorbing member of the present invention (2) can exhibit an excellent collision energy absorption ability in both end face collision and side collision.

[0025]

According to the present invention, one type of pressing tool can be used to form a target irregular cross-sectional shape from a raw pipe of various pipe outer diameter sizes by one pressing, and therefore it can be used as a collision energy absorbing member. It is possible to easily and inexpensively manufacture a suitable deformed pipe, and to provide a collision absorption energy absorbing member having a single pipe structure or a double pipe structure that can exhibit excellent collision energy absorption resistance by using this deformed pipe. It has a remarkable effect.

[Brief description of drawings]

FIG. 1 is a stereo schematic diagram illustrating an embodiment of the present invention (1).

FIG. 2 is a schematic cross-sectional view showing an example of a metal pipe deforming process according to the present invention (1).

FIG. 3 is a three-dimensional schematic diagram (a: double-tube structure, b: single-tube structure) showing a structural example of the present invention (2).

FIG. 4 is a graph showing a relationship between absorbed energy and an outer diameter compressibility in an end face collision test.

FIG. 5 is a graph showing the relationship between maximum bending load × absorbed energy and outer diameter compressibility in side impact test results.

FIG. 6 is a three-dimensional view showing an example of a collision energy absorbing member proposed in Japanese Patent Application No. 2001-334024.

FIG. 7 is an explanatory diagram showing how a collision load is applied to a front side member.

[Explanation of symbols]

1 Inner tube (deformed tube) 2 outer tube 3 metal tubes 4,4a Comb type press jig 5,5a comb teeth 6,6a comb gap 7 cavities 8 Single axis press 11 Maximum diameter of inner pipe 12 Recessed mutual contact part 20 front side members 21 bumper 22 Collision load

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takaro Iguchi             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. F term (reference) 3J066 AA02 AA23 BA03 BB01 BC01                       BD07 BF02 BG08

Claims (4)

[Claims] 1. A pair of comb-type press jigs in which comb teeth are fitted into a mating comb gap to form a cavity, a metal tube is inserted into the cavity, and the cavity is reduced in diameter by a uniaxial press. A method of forming a metal tube, comprising the step of compression-molding a metal tube. 2. The method for forming a metal tube according to claim 1, wherein the cavity is a cavity having a rotationally symmetrical cross section. 3. The method for forming a metal pipe according to claim 1, wherein the width of the comb teeth is 1 to 30% of the outer diameter of the metal pipe before compression molding. 4. The metal pipe to be put in the cavity is a steel pipe having a wall thickness-to-outside diameter ratio of 0.2 to 5%, and the outer diameter compression rate in compression molding is set to 20 to 70%. A collision energy absorbing member using a deformed tube formed by the forming method described in 1.