JP5616877B2 - Bending method of aluminum alloy hollow extruded section, aluminum alloy hollow extruded section and automobile battery frame manufacturing method using this method, automobile battery frame and seat frame structure manufacturing method, and seat frame structure - Google Patents

Description

  The present invention relates to a method for bending an aluminum alloy hollow extruded shape and an aluminum alloy hollow extruded shape using the method, and more particularly to an aluminum alloy hollow extruded shape effective when bending with a small bending radius. The present invention relates to a bending method and an aluminum alloy hollow extruded shape. Furthermore, the present invention relates to an automobile battery frame manufacturing method, an automotive battery frame, a seat frame structure manufacturing method, and a seat frame structure using the hollow extruded profile bending method.

  FIG. 9 shows a perspective view of a frame-like frame made of a hollow extruded shape member. In many structural parts, a frame-like closed cross-section frame is arranged on the outer peripheral portion in order to ensure the rigidity or strength of the part. In recent years, there has been a strong demand for reducing the weight of automobile bodies, especially in automobiles, and the application of aluminum alloys to such structural parts has been desired. In particular, aluminum alloy hollow extruded profiles (hereinafter also simply referred to as “hollow extruded profiles”) have higher specific strength than steel plates and aluminum alloy sheets, and are expected to be applied to such frames.

  The hollow extruded profile has a high degree of freedom in cross section, and it can be designed relatively freely, so there is an advantage that weight reduction can be expected by thickness distribution of the cross section and structural optimization, but it is uniform in the longitudinal direction, There is also a problem of linear shape. For this reason, when forming a frame-like frame, the hollow extruded profile is bent {see FIG. 9 (a)}, or a plurality of straight extruded profiles are joined by welding or the like {FIG. 9 (b)} needs to be manufactured. In many cases, such structural parts (frame-shaped frames) have severe shape constraints inside and outside the frame-shaped frame from the viewpoint of avoiding interference with other parts. For this reason, when a hollow extruded profile is bent, bending with a relatively small bending radius is often required, and avoiding breakage and buckling during bending is a problem.

  Usually, when a frame-shaped frame is manufactured by welding a plurality of direct materials, it is possible to manufacture these direct materials by joining them at a substantially right angle. However, there is a problem that variations in shape accuracy are likely to occur due to thermal deformation during welding, and depending on the material, the strength is reduced due to thermal effects during welding. Further, the welding cost is higher than the bending cost, and the cost increase becomes a problem. In addition, mechanical joining by means of fastening means such as bolts is conceivable. However, compared with all-around welding or plastic working, there is a problem that the strength of the joint is lowered due to point joining. Considering the above points comprehensively, it is desired that the frame-like frame is constituted by a bent product having a small bending radius.

  A draw bender or a press bender is often used for the bending process of the hollow extruded section described above. In these processes, in order to suppress buckling wrinkles and cross-sectional deformation of the bending inner wall, a tool generally called a cored bar is inserted into the hollow extruded profile, and bending is performed while maintaining the cross section to some extent. However, there is a problem that the bending outer wall tends to be broken particularly in bending with a small bending radius. In addition, when such a mandrel is not used, cross-sectional deformation becomes remarkable, and there arises a problem that the surface accuracy or appearance properties necessary for joining with other parts cannot be obtained.

  The aluminum alloy hollow extruded section has a smaller elongation than a conventionally used steel pipe and is likely to break. In particular, as the strength of the material increases, the elongation tends to decrease. As a part requiring high strength, processing defects are more likely to occur, and the shape of a product that can be molded is limited. In order to suppress breakage and cross-sectional deformation during bending of such a hollow extruded profile, the following proposals have been made.

  For example, in order to suppress both breakage and wrinkles during bending of metal pipes, a technique for suppressing breakage and wrinkles by improving the elongation of the material by warm forming using high-frequency heating or the like has been disclosed. (See Patent Document 1). However, in such processing in the warm region, there are problems in that the processing speed is reduced to avoid breakage, the cost is increased due to heating, the material changes due to temperature rise, and the shape accuracy deteriorates due to thermal deformation depending on the material.

  Therefore, as a technique for solving the various problems newly generated, a technique of bending a hollow extruded shape with high accuracy with a small bending radius by cold working is most desired. For this reason, several proposals have been proposed to prevent bending breakage at a small bending radius by bending while bending the inner wall of the hollow extruded shape member into the cross section inside (Patent Documents 2 to 6). reference). The features of the techniques disclosed in these Patent Documents 2 to 6 are that the inner wall of the bend is recessed inward of the cross section, and the height of the cross section is locally reduced or the bend neutral axis is moved outward in the bend direction. This is to reduce the amount of strain generated on the wall.

  In particular, the technique of Patent Document 6 proposes a method of preventing breakage by positively moving the bent inner wall to the inner side of the cross section by bending the side wall of the hollow extruded shape member in advance after bending. (See Patent Document 6).

  Furthermore, a technique is also disclosed for achieving both the cross-section processing and ensuring the shape accuracy by adding hydroform molding that applies internal pressure from the inside of the hollow extruded profile after bending the hollow extruded profile (Patent Document). 7).

Japanese Patent No. 2679340 JP-A-08-66727 Japanese Patent No. 3179384 Japanese Patent Application Laid-Open No. 2002-267338 JP 2003-139180 A Japanese Patent No. 4320856 Japanese Patent No. 4259075

  However, the techniques disclosed in Patent Documents 2 to 7 have the following problems.

  In the techniques disclosed in Patent Documents 2 to 6, the bent inner side wall is greatly recessed inside the cross section, but at this time, since it is not restrained by the mold, a concave shape is formed, and the shape accuracy of this part is improved. There is a problem that it is difficult to guarantee. In addition, when the side wall is convexly deformed to the outside of the cross section due to the deformation of the inner wall of the bend as in Patent Document 3, interference with other parts and joining are often problematic.

  In the technique disclosed in Patent Document 6 described above, convex deformation to the outside of the cross section can be suppressed by providing the side wall with a concave portion on the inside of the cross section, but the bent inner wall is greatly recessed on the inside of the cross section by buckling. The problem that it is difficult to ensure the accuracy of the inner wall of the bending due to deformation is the same as in Patent Documents 2 to 5. And when a bending inner side wall is dented greatly in this way, a deformation | transformation of a bending outer side wall will also concentrate on the narrow area | region of a longitudinal direction. Along with this, as shown in FIG. 5 of Patent Document 3, the bent outer wall also tends to be locally recessed in the cross section, and there is a problem that it is difficult to ensure the shape accuracy of the bent inner and outer walls.

  The technique disclosed in Patent Document 7 described above requires that the end be clamped in order to apply hydraulic pressure from the inside of the shape member, resulting in poor material yield or increased processing time due to application of hydraulic forming. Cost increases due to such problems.

An object of the present invention is a method of bending an aluminum alloy hollow extruded shape which can be bent with a relatively small bending radius by cold working and can easily ensure the surface accuracy of the inner wall and the outer wall of the bend, and the bending. An object of the present invention is to provide an aluminum alloy hollow extruded shape bent by a processing method. It is another object of the present invention to provide an automotive battery frame manufacturing method, an automotive battery frame and a seat frame structure manufacturing method, and a seat frame structure using the hollow extruded shape bending method.

In order to achieve this object, the invention according to claim 1 of the present invention provides:
A bending method of an aluminum alloy hollow extruded section,
In the case of bending the hollow extruded profile, at least the region of the side wall that is substantially parallel to the bending inner radius (r) direction of the hollow extruded profile is formed on the inner side of the cross section of the hollow extruded profile. A first step of forming a recess and a predetermined recess extending in the longitudinal direction of the hollow extruded profile;
After the first step, there is on a straight line connecting the position of the center (θ / 2) Bending angle (theta) when subjected to the bending work with the center P ₁ of the inner radius (r), and the bending processing the rotation center P ₂ point set at a predetermined position distant from the center P ₁ as seen from the region to be applied, the movable die provided near the bending outer wall of the cylindrical workpiece a second step of the performing bending of the cylindrical workpiece while rotating relative to the rotation center P _2,
This is a method of bending an aluminum alloy hollow extruded section characterized by comprising:

The invention according to claim 2 is the invention according to claim 1,
The length D in the longitudinal direction of the hollow extruded profile of the predetermined groove is defined by the following formula (1) from the bending start point on the side wall when the hollow extruded profile is bent using a bending die. It is characterized by satisfying the length.
H: Height of side wall B: Width of bent inner wall supported by side wall or middle rib

The invention according to claim 3 is the invention according to claim 1 or 2 , wherein the hollow extruded profile has a substantially rectangular cross-sectional shape, and a corner of the cross-section is chamfered with a radius of 3 mm or more. It is characterized by that.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the hollow extruded profile has a material temperature of 200 before at least the second step of bending. It is characterized by being a 6000 series or 7000 series aluminum alloy that has been subjected to a heat treatment at a temperature of 0 ° C. or more and 20 seconds or less (excluding zero).

The invention according to claim 5 is an aluminum alloy hollow extruded shape that is bent by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4 .

The invention described in claim 6 is an aluminum alloy hollow that is bent into an L-shape, a U-shape or a B-shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. An automotive battery frame manufacturing method characterized by using an extruded profile as a part of an automotive battery frame.

The invention described in claim 7 is an aluminum alloy hollow that is bent into an L shape, a U shape, or a B shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. An automotive battery frame characterized in that an extruded profile is partially used.

The invention described in claim 8 is an aluminum alloy hollow which is bent into an L shape, a U shape or a B shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. A method for manufacturing a frame structure for a seat, wherein the extruded profile is used as a part of the frame structure for the seat.

The invention described in claim 9 is an aluminum alloy hollow that is bent into an L-shape, a U-shape or a B-shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. A seat frame structure characterized by using an extruded profile partly.

As described above, the present invention
A bending method of an aluminum alloy hollow extruded section,
In the case of bending the hollow extruded profile, at least the region of the side wall that is substantially parallel to the bending inner radius (r) direction of the hollow extruded profile is formed on the inner side of the cross section of the hollow extruded profile. A first step of forming a recess and a predetermined recess extending in the longitudinal direction of the hollow extruded profile;
After the first step, there is on a straight line connecting the position of the center (θ / 2) Bending angle (theta) when subjected to the bending work with the center P ₁ of the inner radius (r), and the bending processing the rotation center P ₂ point set at a predetermined position distant from the center P ₁ as seen from the region to be applied, the movable die provided near the bending outer wall of the cylindrical workpiece since the has a second step for bending the cylindrical workpiece while rotating relative to the rotation center P _2,
It can be bent with a relatively small bending radius by cold working, and it can be bent with this bending method, as well as a bending method of an aluminum alloy hollow extruded profile that is easy to ensure the surface accuracy of the inner wall and the outer wall. A hollow extruded shape made of an aluminum alloy can be provided. Furthermore, an automobile battery frame manufacturing method, an automotive battery frame and a seat frame structure manufacturing method, and a seat frame structure using the hollow extruded profile bending method can be provided.

It is a schematic cross section for demonstrating the bending method of the aluminum alloy hollow extrusion shape material of one Embodiment of this invention. It is a schematic explanatory drawing for demonstrating the state of the side wall at the time of performing the bending method. It is the vertical crushing test figure of the aluminum alloy hollow extrusion shape material, and the evaluation index figure which evaluates the wrinkle at the time of buckling by the test. It is a characteristic view which shows the relationship between the amount of compressive strains ((epsilon)) by the same longitudinal crush test, and {the average wavelength (lambda) ave of a wrinkle of a bending inner side wall / the width B of a bending inner side wall}. It is a schematic cross section for demonstrating the bending method of the aluminum alloy hollow extrusion shape material of other embodiment of this invention. It is a schematic explanatory drawing for demonstrating the other cross-sectional shape of aluminum alloy hollow extrusion shape materials. It is a perspective view for demonstrating the generation | occurrence | production state of the wrinkle of the bending inner side wall in the Example at the time of giving the bending method of this invention. (A)-(c) is a perspective view for demonstrating the presence or absence of a fracture | rupture of the bending outer wall in the Example, (d) is explanatory drawing for demonstrating the evaluation result of the distortion state of a bending outer wall. It is a perspective view which shows the structure of the frame-shaped frame of a prior art example.

  Hereinafter, a method for bending an aluminum alloy hollow extruded section according to the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a schematic cross-sectional view for explaining a method of bending an aluminum alloy hollow extruded profile according to an embodiment of the present invention. FIG. 1 (a) is a front view showing a state where the hollow extruded profile is set in a bending mold. Sectional drawing, (b) is a side sectional view showing a first step of providing a concave groove in the side wall of the hollow extruded profile before bending, and (c) is a second diagram for bending the hollow extruded profile. It is front sectional drawing which shows this process.

  In FIG. 1, reference numeral 1 denotes a hollow extruded shape made of an aluminum alloy whose cross section is, for example, a square shape, 1 a is a bent outer wall, 1 b is a bent inner wall, 1 c is a left side wall, 1 d is a right side wall, and 2 is a predetermined groove 3. A pressing die for forming, 4 is a bending die, 5 is a back holding die, and 6 is a moving die.

Figure 1 (a) shows a state curved surface equipped with a bending molds 4 cylindrical workpiece 1 provided the radius of curvature r from the center P _1.

  FIG. 1 (b) shows a hollow extruded profile 1 set as shown in FIG. 1 (a) (width of bent outer wall 1a and bent inner wall 1b: B, height of left side wall 1c and right side wall 1d: H ) Of the left side wall 1c and the right side wall 1d substantially parallel to the bending radius (r) direction, respectively, by using the pressing mold 2 respectively, the length D from the bending start point where the concave groove 3 is in contact with the straight line X {FIG. 1 (a) The step {first step} provided by press working so as to be referred to is shown. The concave groove 3 is provided at the center in the height direction of the left side wall 1c and the right side wall 1d so as to correspond to the entire length of the region to be bent as shown in FIG. The concave groove 3 is not necessarily provided at the center in the height direction of the left side wall 1c and the right side wall 1d as in the present embodiment, but in order to obtain a deformed shape that is more symmetrical, the left side wall 1c and the right side wall 1d Is preferably provided at the center in the height direction. The first step is provided in order to easily cause dent deformation of the hollow extruded profile 1 to the inside of the square-shaped cross section in each of the left side wall 1c and the right side wall 1d, and the shape is formed as necessary. The depth and the like are selected for convenience.

FIG. 1 (c) shows a hollow extruded profile 1 in a state where a hollow extruded profile 1 in which a concave groove 3 is provided in each of a left side wall 1c and a right side wall 1d is sandwiched between a bending mold 4 and a back surface holding mold. a hollow extruded shape member 1 for example bending angle theta = 90 ° while rotating the movable die 6 provided near the outer side wall 1a in the bending direction indicated by the arrows around the rotational center P ₂ bending A step of performing bending processing (second step) is shown. The rotation center P ₂ is on a straight line connecting the center P ₁ and the center (θ / 2 = 45 °) of the bending angle (θ = 90 °) of the hollow extruded shape 1 and is a hollow extruded shape. 1 of bending is the center which is set at a position farther from the center P ₁ as viewed from the region side to be subjected.

  Since the first process and the second process as described above are included, it is possible to perform bending with a relatively small bending radius by cold working, and it is easy to ensure the surface accuracy of the bending outer wall {bending outer wall 1a Can be avoided. } A method for bending an aluminum alloy hollow extruded shape and an aluminum alloy hollow extruded shape bent by this bending method can be provided. Furthermore, an automobile battery frame manufacturing method, an automotive battery frame and a seat frame structure manufacturing method, and a seat frame structure using the hollow extruded profile bending method can be provided.

FIG. 2A is a schematic explanatory view for explaining the state of the left side wall 1c of the hollow extruded profile 1 when the bending method of the present invention shown in FIG. 1 is applied, and FIG. It is an expansion schematic explanatory drawing of the left side wall 1c. As described above, by rotating movement around the rotational center P ₂ a movable die 6, the respective heights H of the left wall 1c and the right wall 1d of predetermined grooves 3 are each provided is reduced Such deformation is promoted (see FIG. 2). Further, since the bending inner wall 1b is deformed so as to be pressed against the bending mold 4 at the time of the bending process, the bending inner wall 1b is not easily deformed by unevenness such as wrinkles, and the surface accuracy of the bending inner wall is ensured. It's easy to do. In addition, the bending method according to the present invention can suppress the concentration of strain, that is, the strain amount is smaller by making the deformation region of the bending outer wall wider than the techniques described in Patent Documents 2 to 6 described above. It is difficult to break. And the amount of distortion is small, and it is characterized in that it is easy to ensure the accuracy of the outer wall of the bending by acting with a constraint by a tool.

  In the first step, at least a region of the left side wall 1c and the right side wall 1d that is substantially parallel to the bending radius direction of the hollow extruded profile 1 is recessed on the inner side of the cross section of the hollow extruded profile 1, and Since the predetermined concave groove 3 extending in the longitudinal direction of the hollow extruded shape member 1 is provided, it is difficult to cause deformation other than the region to be bent without using a cored bar, and the surface accuracy of the bent outer wall 1a. Etc., that is, it is easy to ensure the shape accuracy {that is, “break” of the bent outer wall 1a can be avoided}. As a result, there is an advantage that problems such as poor insertion of the cored bar during bending are less likely to occur. Moreover, it is suitable for the bending of a long object in which the insertion distance of the core bar into the hollow extruded member 1 is long because the hollow extruded member 1 can be bent with good shape accuracy without using the core bar. In addition, there is an advantage that the present invention can be easily applied to the hollow extruded shape member 1 that needs to be bent a plurality of times.

Further, in the second step (bending), the hollow extruded profile 1 (width B of the bent outer wall 1a and the bent inner wall 1b) and (height H of the left side wall 1c and the right side wall 1d) and the cross section Depending on the condition of the wall thickness t (described later), a convex wrinkle that protrudes outward in the cross-section direction occurs around the bending end point of the bending inner side wall 1b. In order to reduce this wrinkle, the length D of the predetermined groove 3 is the bending start point when the hollow extruded profile 1 is bent using the bending mold 4 (the hollow extruded profile 1 shown in FIG. 1). It is desirable that the length is defined so as to satisfy the length defined by the following formula (1).

  The reason why it is desirable to provide the length D of the predetermined groove 3 so as to satisfy the length defined by the above formula (1) will be described below with reference to FIGS.

  The convex wrinkles of the bent inner wall 1b are caused by compressive stress. As shown in FIG. 1 above, since the bending start point side of the hollow extruded shape member 1 is in contact with the bending mold 4 in advance, the wrinkle toward the outer side of the cross section hardly occurs. However, on the bending end point side of the hollow extruded shape 1, there is no tool that suppresses the convex deformation facing the outer side of the cross section of the bending inner side wall 1b in the middle of processing, and thus wrinkles may occur. . However, the inventor performs at least bending of the left side wall 1c and the right side wall 1d substantially parallel to the bending inner radius (r) direction of the hollow extruded shape 1 when the hollow extruded shape 1 is bent. In addition, a concave groove 3 having a length D defined by the above equation (1) extending in the longitudinal direction of the hollow extruded shape member 1 and extending in the longitudinal direction of the hollow extruded shape member 1 is provided. The new knowledge that wrinkles are greatly eased.

  And about the length D of this ditch | groove 3, it discovered that a convex wrinkle could be suppressed by setting according to the knowledge acquired from the crushing test result of the rectangular cross-section shape material. Specifically, the test material {aluminum alloy 6063-T1 tempered material, cross-sectional shape (dimension B × B, thickness t, C surface added to corner) × length H} shown in FIG. 3A is used. Then, as a result of conducting a longitudinal crush test as shown in FIG. 3B {crushing speed 2 mm / sec, no lubrication}, knowledge as shown in FIG. 4 was obtained. That is, the average wavelength λave of wrinkles {see FIG. 3C) is about 0. 0 of the width B of the bent inner wall 1b supported by the left side wall 1c, the right side wall 1d, the side wall, or the middle rib (see FIG. It is about 8 to 1.6 times (see FIG. 4). That is, by setting the concave groove 3 so as to cover the bending portion and the longitudinal direction of the tube so as to cover the region corresponding to the wrinkle wavelength, the compressive stress applied to the bending inner wall 1b can be greatly reduced. , Convex wrinkles can be suppressed. This length is the length D defined by the above formula (1). Even if the length D of the concave groove 3 is set longer than the length defined by the above formula (1), it can be bent without any problem, but naturally, the region where deformation occurs is enlarged. Therefore, since it is more advantageous to ensure the shape accuracy after the bending process, it is preferable that the length D of the concave groove 3 is provided in the range represented by the above formula (1). It can be said.

  The length D of the predetermined groove 3 is defined by the following formula (1) from the bending start point on the left side wall 1c and the right side wall 1d when the hollow extruded profile 1 is bent using the bending die 4. It is preferable to provide so as to satisfy the length. This is because there is no problem even if it is provided on the end side of the bending start point, but the deformation region is naturally enlarged. On the other hand, if it moves to the bending part side from the bending start point, the deformation of the left side wall 1c and the right side wall 1d during the bending process is less likely to occur, resulting in the deformation of the cross section of the hollow extruded shape member 1 Is likely to occur.

Moreover, in order to avoid reliably the fracture | rupture of the bending outer side wall 1a of the hollow extruded section 1, the bending outer side strain amount (Formula (2) shown below in the center ((theta) / 2) position of the hollow extruded section 1 ( It is desirable that the relationship between [epsilon]) and the elongation at break ([delta]) in uniaxial tensile deformation of the hollow extruded profile 1 satisfy the following formula (3).
R: initial distance between the bending in the side wall of the center of rotation P ₂ and the hollow extruded shape member of the movable mold

That is, the above formula (2) is obtained by calculating the bending outer strain amount (ε) at the bending angle center (θ / 2) from the geometric shape shown in FIG. initial distance by determining the position of the R, bending the outer strain amount of the rotation center P ₂ and bending the side wall 1b of the cylindrical workpiece 1 of the movable mold 6 (epsilon) elongation at break in a tensile uniaxial material ([delta]) It is possible to make the following, and the breakage can be surely avoided.

  In addition, the cross-sectional shape of the hollow extruded profile 1 to be bent is preferably substantially rectangular in consideration of securing the joint surface with other parts, but it prevents bending fracture at the left side wall 1c and the right side wall 1d. From this point of view, it is desirable that R having a radius of 3 mm or more is provided at the corner of the cross section. As shown in FIG. 2, when the bending method is performed, the left side wall 1c and the right side wall 1d are deformed so as to be recessed inside the cross section, and at this time, the respective surfaces of the left side wall 1c and the right side wall 1d are locally formed. Bending strain occurs. Therefore, if R provided at the corner of the cross section is reduced, this bending strain also increases, and bending fracture may occur.

(Other embodiments)
FIG. 5 is a schematic cross-sectional view for explaining a method of bending an aluminum alloy hollow extruded shape according to another embodiment of the present invention. 5 is the same as FIG. 1 except that the bending angle θ is smaller than that of the embodiment shown in FIG. The rotation center P ₂ of the movable mold 6 is set on a straight line connecting the position of the center (θ / 2) of the bending radius center P ₁ and the bending angle of bending molds (theta). Thereby, the amount of reduction in the cross-sectional height H of the hollow extruded profile 1 at the bending end position can be reduced to zero.

  In addition, in this embodiment, although the cross-sectional shape of the hollow extrusion shape material 1 demonstrated the example of a square shape (rectangle without a middle rib), it is not necessarily limited to this. For example, as shown in FIG. 6, the present invention can be applied even to a cross-sectional shape provided with a middle rib 1 e such as a day shape or a rice field. 6 (a), it is difficult to provide the concave groove 3 in the first step in the middle rib 1e. Therefore, the concave groove 3 is provided in the side wall located on the outer periphery of the cross section. Thus, the middle rib 1e is deformed. Moreover, when the middle rib 1e is connected to the intermediate position of the side wall as shown in FIG. 6B or FIG. 6C, it can be dealt with by providing the concave groove 3 around this.

  Moreover, it is desirable that the aluminum alloy hollow extruded shape used in the bending process of the present invention is made of a 6000 series or 7000 series alloy in view of the strength of the material. More preferably, in order to prevent bending fracture at the outer wall of the bend, at least the material arrival temperature is 200 ° C. or more and 20 sec or less (excluding zero) before the bending process (second step). It is most desirable to perform bending in a cold state within 3 hours after the heat treatment for a period of time. It is known that when such pre-bending (second process) heat treatment is performed, the local elongation of the material increases, and it can be bent by using it at sites where significant bending deformation occurs, such as side walls. It can be said that breakage at the deformed portion can be prevented.

  In addition, the bending method of the present invention is particularly effective in preventing breakage and ensuring shape accuracy in processing with a small bending radius and a large bending angle θ. Also, the aluminum alloy hollow extruded shape bent as described above is suitable for a frame structure for a transportation machine such as an automobile from the viewpoint of weight reduction. In particular, it is suitable for use in L-shaped, U-shaped or B-shaped frames formed by bending a plurality of bending angles θ = 90 °, and used for a part of a frame structure of an automobile battery frame or a seat. Is desirable.

  In order to confirm the effect of the bending method of the present invention, the dynamic explicit software LS-DYNA was used and verified by simulation. As a hollow extruded shape 1, a T1 tempered material of a 7000 series extruded shape having a length L, □ 40 mm (B-shaped, B = 40 mm × H = 40 mm, cross-sectional angle R = 5 mm, wall thickness t = 2 mm) Using. It is assumed that a concave groove 3 having a depth of 5 mm is provided by pressing in the center of the side walls 1c and 1d in the height H direction over the entire length of the bent portion.

In addition, in the center in the height H direction of each of the left side wall 1c and the right side wall 1d,
(A) When the concave groove 3 having a length D = 120 mm is provided (that is, D = (r + H / 2) θ + 1.0B, invention example),
(B) When the concave groove 3 having a length D = 80 mm is provided (that is, D = (r + H / 2) θ, invention example)
(C) Three conditions were prepared when the concave groove 3 was not provided (comparative example).
Other conditions are common: cold working, bending inner radius r = 30 mm, initial distance R = 60 mm between the rotation center P ₂ of the moving mold 6 and the bending inner wall 1 b of the hollow extruded shape 1, bending angle θ = 90 (deg), and bending is performed without using a cored bar.

  FIG. 7 shows the state of occurrence of wrinkles on the bent inner wall 1b after bending under the above three conditions, and FIG. 8 shows the evaluation result of the strain state of the bent outer wall 1a. As shown in FIGS. 8A, 8 </ b> B, and 8 </ b> D, in the above-described invention examples (a) and (b) provided with the recessed grooves 3, the generation of the strain amount of the bent outer wall 1 a is suppressed. That is, by applying the present invention, it was confirmed that bending with a small bending radius can be performed while avoiding breakage of the bending outer wall 1a. Further, as shown in FIG. 7 (a), in the invention example in which the length D of the groove 3 is made longer than the length of the bent portion of the hollow extruded profile 1, the uneven wrinkles at the bending end portion of the bending inner side wall 1b. The depth is 0.3 mm, and the wrinkles are remarkably suppressed, and it can be seen that the predetermined surface accuracy of the bent inner side wall 1b is ensured. On the other hand, the uneven wrinkle depth at the bending end portion of the bending inner wall 1b in FIG. 7B was 1.3 mm. As described above, by adopting the bending method according to the present invention, it is possible to suppress the fracture of the bending outer wall 1a for the first time even when bending is performed with a relatively small bending radius by cold working (bending outer wall). It was found that the predetermined surface accuracy of 1a can be ensured). Furthermore, by setting the length D of the concave groove 3 to a value as shown in the above-described formula (1) {for example, as in the above-described invention example (a)}, the bending inner wall 1b and the bending outer wall 1a It was found that the surface accuracy can be further improved (that is, both the occurrence of wrinkles on the bent inner side wall 1b and the fracture of the bent outer wall 1a can be suppressed).

DESCRIPTION OF SYMBOLS 1 Aluminum alloy hollow extrusion 1a Bending outer wall 1b Bending inner wall 1c Left side wall 1d Right side wall 1e Middle rib 2 Pushing die 3 Concave groove 4 Bending die 5 Back surface holding die 6 Moving die

Claims (9)

A bending method of an aluminum alloy hollow extruded section,
In the case of bending the hollow extruded profile, at least the region of the side wall that is substantially parallel to the bending inner radius (r) direction of the hollow extruded profile is formed on the inner side of the cross section of the hollow extruded profile. A first step of forming a recess and a predetermined recess extending in the longitudinal direction of the hollow extruded profile;
After the first step, there is on a straight line connecting the position of the center (θ / 2) Bending angle (theta) when subjected to the bending work with the center P ₁ of the inner radius (r), and the bending processing the rotation center P ₂ point set at a predetermined position distant from the center P ₁ as seen from the region to be applied, the movable die provided near the bending outer wall of the cylindrical workpiece a second step of the performing bending of the cylindrical workpiece while rotating relative to the rotation center P _2,
A method for bending a hollow extruded profile made of an aluminum alloy, comprising: The length D in the longitudinal direction of the hollow extruded profile of the predetermined groove is defined by the following formula (1) from the bending start point on the side wall when the hollow extruded profile is bent using a bending die. 2. The method for bending an aluminum alloy hollow extruded section according to claim 1, wherein said length is satisfied.

H: Side wall height
B: Width of bent inner wall supported by side wall or middle rib 3. The aluminum alloy hollow extruded shape according to claim 1, wherein a cross-sectional shape of the hollow extruded shape is substantially rectangular, and a corner of the cross section is chamfered with a radius of 3 mm or more. Bending method. The hollow extruded profile is a 6000 series that has been subjected to a short-time heat treatment at a material arrival temperature of 200 ° C. or higher and a processing time of 20 sec or less (excluding zero) before bending at least in the second step. 4. The method of bending an aluminum alloy hollow extruded section according to any one of claims 1 to 3 , wherein the method is a 7000 series aluminum alloy. An aluminum alloy hollow extruded shape that is bent by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4 . An aluminum alloy hollow extruded shape that has been bent into an L shape, a U shape, or a B shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4 is used for an automotive battery frame. An automobile battery frame manufacturing method characterized by being used as a part. A part of the aluminum alloy hollow extruded shape bent into an L shape, a U shape or a B shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. A battery frame for automobiles. 5. A frame structure for a seat comprising an aluminum alloy hollow extruded shape bent into an L shape, a U shape, or a B shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. A method for manufacturing a frame structure for a seat, characterized by being used as a part of the seat. A part of the aluminum alloy hollow extruded shape bent into an L shape, a U shape or a B shape by the method of bending an aluminum alloy hollow extruded shape according to any one of claims 1 to 4. A frame structure of a seat characterized by comprising: