JP2010221742A - Bumper stay and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bumper stay preventing the generation of breaking in collision with a vehicle body, preventing a resultant reduction in a load and being excellent in an energy absorption property when a 6,000 or 7,000 series aluminum alloy extrusion material subjected to aging treatment is applied to the bumper stay. <P>SOLUTION: The bumper stay is constituted of a front flange 8 positioned on a bumper beam side; a rear flange 9 positioned on a side member; and two or more ribs 11, 12 extending in a longitudinal direction and connecting the front flange to the rear flange. Plate thickness of an inner rib 11 is made thinner than an outer rib 12, and at a central part in a width direction, friction/stirring treatment is applied in an extrusion direction. After friction/stirring, artificial aging treatment (T5, T7) is applied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bumper stay that is made of an aluminum alloy hollow extruded shape and is lightweight and excellent in collision safety. Specifically, the reforming treatment is locally applied to maintain a material strength and at the time of a vehicle collision. The present invention relates to a bumper stay excellent in energy absorption, in which load reduction due to generated cracks is prevented.

  In automobiles and vehicles, bumpers are disposed on the front and rear of the vehicle body for the purpose of absorbing the impact at the time of collision. This bumper has a bumper beam (bumper reinforcing material) manufactured from a rod-shaped metal hollow material, and the bumper beam is provided through a bumper stay in a vehicle body such as a side member provided at a front end portion or a rear end portion of the vehicle body. It is fixedly attached to the frame. For these bumper stays, an aluminum alloy hollow material is used for weight reduction. Aluminum extrudates are frequently used as an effective means for weight reduction because they can obtain a complicated cross-sectional shape having an arbitrary thickness distribution that is difficult with iron in addition to being lightweight. In particular, high strength 6000 series alloys and 7000 series alloys are often applied.

Conventionally, the performance required for the bumper has been a challenge for improving the strength because it was car body protection at the time of a light collision, but in recent years, the ability to absorb energy by the bumper being crushed and deformed at the time of the car body collision is required. It has been. Therefore, the role of a bumper system using a bumper beam and a bumper stay is becoming important in absorbing energy at the time of collision.
In the bumper stay (lateral crush type stay) having a hollow cross section with the vertical direction of the vehicle body as the extrusion direction, the bumper stay is made uneven as in Patent Document 1, for example, for the purpose of improving the energy absorption performance at the time of bumper stay collision. There are some which control the deformation form of the hollow part by tilting the rib as in Patent Document 2 or by bending the rib as in Patent Document 3.
However, when the bumper stay is crushed and deformed in the event of a collision, cracking is likely to occur if a high-strength material such as an aging alloy such as a 6000 series alloy or a 7000 series alloy is applied.

On the other hand, Patent Documents 4 and 5 are known as surface modification techniques for aluminum alloys. In either case, a rotary tool equipped with a probe is used to frictionally stir the surface of the aluminum alloy to improve the mechanical properties of the aluminum alloy. To make it a shock energy absorbing part and to give the metal structure a shock absorbing function, Patent Document 5 describes that the crystal grain size is controlled to locally increase the strength and hardness. Are listed.
Patent Documents 6 and 7 describe that an aluminum structure is manufactured by utilizing the fact that the joint of friction stir welding can be bent.

JP 2002-12103 A JP 2003-31399 A JP 2006-335241 A Japanese Patent No. 3207376 Japanese Patent No. 4006515 JP 2006-30562 A JP 2007-75839 A

  The present invention has been made in view of the above problems when a high-strength material such as a 6000 series alloy or a 7000 series alloy subjected to aging treatment is applied to a bumper stay. An object of the present invention is to provide a bumper stay excellent in energy absorption by preventing the occurrence of cracking at the time of a vehicle body collision and preventing a decrease in load due to the reduction in weight.

The present invention relates to a bumper stay made of a hollow aluminum alloy material, and is characterized in that a friction stirring process is performed on a portion that is easily buckled at the time of a vehicle body collision.
In the present invention, the friction stir processing is based on the well-known principle of friction stir welding (FSW) using a rotary tool equipped with a probe, and friction stirs the material of the bumper stay with a predetermined processing width. It is to modify the material. By subjecting the bumper stay to a modification treatment by friction stirring, the modified portion is softened and the bendability is improved. Therefore, if a part that is prone to cracking at the time of a collision is modified, the bending workability of the part is improved and it becomes difficult to crack at the time of a vehicle collision, preventing a sudden load drop accompanying the cracking and improving the energy absorption performance Can be made.

In the bumper stay, as a portion that is likely to buckle at the time of a vehicle body collision (a portion where buckling is assumed at the time of collision), a certain portion is specified from the feature of the cross-sectional shape of the bumper stay.
A front flange located on the bumper beam side and a rear flange located on the side member side, which is disposed between the bumper beam and the side member of the automobile body and is made of an aluminum alloy extruded shape with the vertical direction of the vehicle body as the extrusion direction. In the case of a typical lateral crush type bumper stay that is composed of two or more ribs extending in the front-rear direction and connecting the front flange and the rear flange, the portion that is likely to buckle at the time of a vehicle collision is a rib. It is the center part of the width direction (front-back direction) of a rib. In this case, along the extrusion direction (preferably the total length in the extrusion direction), either or both of the outer ribs on the outermost side in the vehicle body width direction and the inner ribs on the innermost side of the ribs in which the friction stir processing can be performed. Friction stir processing is performed with a predetermined processing width.

Also, in the lateral crush type bumper stay as described above, for example, assuming a barrier collision, the thickness of the inner rib is made thinner than the thickness of the outer rib so that the inner rib is shaped like a dogleg when the bumper stay is collapsed. The cross section may be designed to bend and deform. This is to stabilize the energy absorption by buckling the target site. In this case, the inner rib is a part that is particularly susceptible to buckling deformation, and the central part in the width direction is most likely to buckle. Such a cross-sectional design can limit the buckling part at the time of a vehicle collision, and by applying friction stir processing to the part, local cracks in the bumper stay can be prevented and a sudden load drop It is possible to stabilize the energy absorption performance of the bumper stay.
In the present invention, it is not necessary to apply friction stir processing to all of the parts that are supposed to buckle at the time of a vehicle collision, and at least a part that is likely to buckle preferentially at the time of vehicle collision (for example, the inner rib in the above example). ) Need only be subjected to a friction stirring process.

Since the friction stir processing is performed on a flat surface, the portion (rib) to which the friction stir processing is performed needs to be flat or at least have a flat space with a width where the friction stir processing can be performed. It is desirable that the processing depth of the friction stir processing is 30% or more of the processing portion plate thickness.
Cracks at the time of collision tend to progress linearly along the vertical direction in the bumper stay with the vertical direction of the vehicle body as the extrusion direction, and the friction stir processing needs to move the rotary tool and the bumper stay relative to each other, so friction stir The treatment is desirably performed linearly along the vertical direction (extrusion direction) of the vehicle body of the bumper stay. Since the vicinity of the rib width central portion is easily broken, it is desirable that the friction stir processing is performed so as to pass near the rib width central portion.

The bumper stay is preferably made of a high-strength 6000 series or 7000 series aluminum alloy shape, particularly an extruded shape. Above all, the 7000 series aluminum alloy extruded shape has higher strength than the 6000 series high strength material, and it is easy to crack at the time of collision. However, there is an advantage that the weight can be further reduced. The aluminum alloy is subjected to artificial aging treatment (T5, T7) to increase the strength. As the cross section of the aluminum alloy profile, for example, a substantially rectangular shape having a substantially rectangular outline, such as a substantially mouth shape or a substantially daily shape, can be suitably used.
The 6000 series and 7000 series are heat treatment type aluminum alloy systems defined in JIS, and mean Al-Mg-Si- (Cu) series and Al-Zn-Mg- (Cu) series aluminum alloys, respectively. . T5 and T7 are categorized according to JISH0001.

In the present invention, the artificial aging treatment is preferably performed after the friction stirring treatment.
A bumper system can be manufactured by fixing the bumper stay after the artificial aging treatment to the bumper beam.
Alternatively, in order to reduce the weight of the entire bumper system, the bumper beam is also made of the above-mentioned 6000 series or 7000 series aluminum alloy extruded shape, and both ends in the vehicle width direction are bent to the vehicle body side in a horizontal plane, and the vehicle width is inclined. In many cases, the bumper stay is fixed at both ends in the direction. In this case, the bumper stay before the artificial aging treatment (quality T1 state) subjected to the friction stirring treatment is also used before the artificial aging treatment (quality T1 state). It can be fixed to the bumper beam and artificially aged together.

  According to the present invention, when an aluminum alloy hollow shape member is used for the bumper stay, even when a high-strength 6000 series or 7000 series aluminum alloy hollow shape material is used, cracking at the time of collision is prevented. The load absorption can be prevented and the energy absorption can be improved, and the weight reduction can be achieved while maintaining the performance satisfying the stricter collision safety standards. In particular, those subjected to the artificial aging treatment after the friction stir treatment are highly effective in preventing cracking and improving energy absorption.

It is a perspective view explaining a friction stirring process. It is a figure which shows the effect | action of the change of the hardness by a friction stirring process, and an artificial aging treatment. It is a top view of the bumper system concerning the present invention. It is the top view (c) which shows the top view (a) of the bumper stay which concerns on this invention, a side view (b), and the deformation | transformation at the time of a collision. It is the top view (b) which shows the top view (a) of the other bumper stay which concerns on this invention, and the deformation | transformation at the time of a collision. It is a top view of the other bumper stay which concerns on this invention. It is a perspective view of the bumper stay used for the Example. It is a schematic diagram explaining the evaluation criteria of the load drop (a) and energy absorption amount (b) in an Example.

Hereinafter, the bumper stay according to the present invention will be described with reference to FIGS.
First, FIG. 1 is a diagram illustrating a friction stirring process according to the present invention. In the friction stir processing, the rotary tool 2 having the probe 1 at the tip is rotated at a high speed, the probe 1 is inserted into the aluminum alloy plate 3 (assuming the rib of the bumper stay), and the probe side end face (shoulder) of the rotary tool 1 Then, the plate surface is moved while being pressed, and the probe insertion portion and its vicinity are frictionally stirred at a constant width . If the diameter of the probe 1 is too small, it will break, and if it is large, it will not be stirred just by pushing the tip, so 2-5 mm is desirable. The shoulder diameter may be about 5 to 15 mm.

  The processing depth H of the reforming processing unit 4 (with dots) by friction stirring is determined by the height of the probe 1, and the processing width W is determined by the shoulder diameter of the rotary tool 2. When the thickness of the processing portion is t, (H / t) × 100 ≧ 30 (%) is desirable, and this value is desirably 50 to 100%. The friction stir processing can be performed not only once but also twice or more so that the processing widths overlap (in this case, the processing width increases) or apart.

When the aluminum alloy sheet is subjected to a modification process by friction stirring, the modified part is softened and the bendability is improved. Thereby, the bending workability of the said part improves, it becomes difficult to break at the time of a vehicle body collision, the sudden load fall accompanying a crack can be prevented, and energy absorption performance can be improved.
On the other hand, when the artificial aging treatment is performed after the friction stirring treatment, the softened modified portion is restored to the same strength as the non-treated portion again. However, this does not cause the bendability to deteriorate again, but rather an improvement in bendability is recognized. The reason is not necessarily clear, but it is presumed that the effect of the elimination of the difference in strength between the reforming process part and the non-process part is affected.

  Figure 2 shows the surface of JIS7N01 aluminum alloy extruded material (plate material) subjected to friction stir processing parallel to the extrusion direction using a rotating tool with a probe diameter of 3 mm, a processing depth of 1.7 mm, and a shoulder diameter of 10 mm. It is the graph obtained by measuring the Hv hardness of a process part and a non-process part at intervals of 2 mm perpendicular to an extrusion direction. Among these, Fig.2 (a) shows the measurement result about the board | plate material which performed the friction stirring process with respect to T1, T5, T7 material, FIG.2 (b) performed the friction stirring process with respect to T1 material, and continued. The measurement results of the plate materials subjected to the T5 and T7 treatments (the results of the plate materials not subjected to the T5 and T7 treatments are also displayed) are shown. As shown in FIGS. 2A and 2B, when the friction stir treatment is performed after the artificial aging treatment, the hardness of the modified portion is Hv 20 to 30 points lower than that of the non-treated portion. When artificial aging treatment is performed later, the hardness of the modified portion is recovered to the same extent as the non-treated portion.

  FIG. 3 shows a bumper system 7 including a bumper beam 5 made of an aluminum alloy hollow extruded shape member and bumper stays 6 attached to the back sides of both ends of the bumper beam 5 in the vehicle width direction. The bumper stay 6 includes a front flange 8 positioned on the bumper beam 5 side, a rear flange 9 positioned on the side member side, and two ribs extending in the front-rear direction and connecting the front flange 8 and the rear flange 9 ( It consists of an inner rib 11 and an outer rib 12). The inner rib 11 is longer than the outer rib 12 corresponding to the inclination of both ends of the bumper beam 5, and the plate thickness of the inner rib 11 is thinner than the plate thickness of the outer rib 12. For this reason, when a barrier collision is assumed, for example, the inner rib 11 is most likely to buckle at the center in the width direction.

  4 (a) and 4 (b) are diagrams schematically showing a state (reforming treatment portion 11a) in which a friction stir processing is performed in the widthwise center portion of the inner rib 11 of the bumper stay 6 along the extrusion direction. It is. The bumper stay 6 is reinforced by artificial aging treatment, but the inner rib 11 is excellent in bendability in the reforming treatment portion 11a, and as shown in FIG. Without causing bending deformation at the central portion in the width direction, thereby preventing a sudden drop in load. If necessary, the outer rib 12 can also be subjected to friction stirring.

  FIG. 5A is a diagram schematically illustrating another example of the bumper stay that has been subjected to the reforming process by friction stirring. The sectional shape of the bumper stay 6A itself is the same as that of the bumper stay 6 shown in FIG. 4 (a), but friction stirring treatment ( Modification processing units 11a and 11b) are applied. Also in this case, the inner rib 11 is excellent in bendability in the reforming processing portions 11a and 11b, and as shown in FIG. 5B, the inner rib 11 is bent and deformed in the reforming processing portions 11a and 11b without causing cracks when buckling at the time of collision. This prevents a sudden drop in load.

  FIG. 6 is a diagram schematically illustrating still another example of the bumper stay that has been subjected to the reforming process by friction stirring. The bumper stay 6B has an inner rib 11, an outer rib 12, and an inner rib 13, and the plate thickness becomes thinner in the order of the outer rib 12, the inner rib 13, and the inner rib 11. Therefore, for example, assuming a barrier collision, the inner rib 11 is most likely to buckle at the center in the width direction. The inner rib 11 is subjected to friction agitation processing (modification processing portion 11a) along the extrusion direction at the center in the width direction. In the case of the bumper stay 6B as well, the outer rib 12 can be subjected to a friction stirring process as necessary.

As the bumper beam, an aluminum alloy extruded shape (JIS6N01-T1) having a daily cross section of 70 mm in the longitudinal direction of the vehicle body and 100 mm in the vertical direction of the vehicle body is used, and end bending is performed as shown in FIG. And artificial aging treatment (T5) was performed.
On the other hand, as a bumper stay, an aluminum alloy extruded profile (JIS7N01-T1) having a cross section (see FIG. 3) consisting of front and rear flanges and inner and outer ribs is used, and a bumper consisting of front flanges, rear flanges, inner ribs and outer ribs. Made a stay. The front flange 8 is inclined corresponding to the end of the bumper beam. As shown in FIG. 7, the bumper stay has a width in the vehicle width direction of 70 mm, a vertical height inside the vehicle body of 80 mm, a vertical height outside the vehicle body of 100 mm, and a height of the outer rib of 50 mm. In order to give priority to the buckling of the outer rib in the body collision, the plate thickness (2 mm) of the inner rib 11 is made thinner than the plate thickness (3 mm) of the outer rib.

The following processing was added to each bumper stay. Bumper stays A and B are examples of the present invention, and bumper stay C is a conventional example.
Bumper Stay A:
As shown in FIG. 7, after the friction stir processing (reforming treatment portion 11 a) was performed over the entire width in the extrusion direction near the center in the width direction of the inner rib 11, artificial aging treatment (T5) was performed. The conditions of the friction stir processing were as follows: shoulder diameter of rotating tool: 10 mm, probe diameter: 3 mm, probe height: 1.7 mm, rotation speed: 1650 rpm, feed rate: 300 mm / min, tilt angle: 3 °. In addition, the processing depth H of the friction stir processing was about 80% of the processing part thickness.
Bumper Stay B:
Specimen No. No. 1 was subjected to artificial aging treatment (T5), and The same friction stirring treatment as in No. 1 was performed.
Bumper Stay C:
Specimen No. was not subjected to friction stirring treatment. The same artificial aging treatment (T5) as 1 was performed.

Subsequently, each bumper stay was attached to the back of both ends of the bumper beam. 1-3 bumper systems were manufactured. Test No. 1 is a bumper stay A attached, test No. 2 with a bumper stay B attached, test no. 3 is a bumper stay C attached.
No. 1 to 3 bumper systems were joined to the vehicle body frame, and a barrier collision was made from the front under the same conditions, and the occurrence of cracks in the inner rib 11, the degree of load drop and the amount of energy absorption (EA amount) were investigated. The results are shown in Table 1.

  In Table 1, in the column of cracking, ◯ is given to those in which no cracks occurred in the inner rib 11, △ to those in which minute cracks have occurred, and × to those in which split cracks have occurred, In the column, ○ was given to those where there was no load drop due to cracks, △ was given to those where there was a slight load drop, and × was given to those where there was a sudden load drop due to cracks (evaluation criteria are shown in FIG. 8 ( (See the load-displacement curve in a).) In the column of energy absorption amount (EA amount), No. 3 is marked with x, and Δ is given to those that have improved considerably with reference to this, and ○ is given to those that have further improved (see EA amount-displacement curve in FIG. 8B for the evaluation criteria).

  As shown in Table 1, the conventional test No. In No. 3, a split crack occurred in the inner rib 11, a sudden load drop occurred, and the energy absorption amount was low. In contrast, test no. No. 1 had no cracks in the inner ribs 11 and therefore no load drop due to the cracks, resulting in an increase in energy absorption. In addition, Test No. In No. 2, a minute crack was generated in the inner rib 11, but no load drop due to this was observed, and the energy absorption amount was also No. Test No. 1 that did not reach 1 Increased compared to 3.

DESCRIPTION OF SYMBOLS 1 Probe 2 Rotating tool 3 Aluminum alloy plate 4 Modification processing part 5 Bumper beam 6, 6A, 6B Bumper stay 7 Bumper system 8 Front flange 9 Rear flange 11 Inner rib 11a Modification processing part 12 Outer rib 13 Middle rib

Claims (8)

It is placed between the bumper beam and the side member of the automobile body, and is made of an aluminum alloy extruded shape having a hollow cross section with the vertical direction of the vehicle body as the extrusion direction. A rear flange and two or more ribs extending in the front-rear direction and connecting the front flange and the rear flange, and the outer rib on the outermost side in the vehicle body width direction or the inner rib on the innermost side among the ribs A bumper stay characterized in that either one or both of them is subjected to a friction stirring process along the extrusion direction. The bumper stay according to claim 1, wherein the bumper stay is made of an extruded material of 6000 series or 7000 series aluminum alloy subjected to artificial aging treatment. The bumper stay according to claim 2, wherein the artificial aging treatment is performed after the friction stir treatment. The bumper stay according to any one of claims 1 to 3, wherein friction stir processing is performed over the entire length in the extrusion direction. The bumper stay according to any one of claims 1 to 4, wherein the inner rib is thinner than the outer rib, and the inner rib is subjected to friction stirring. The bumper stay according to any one of claims 1 to 5, wherein a processing depth of the friction stir processing is 30% or more of a processing portion plate thickness. The method for producing a bumper stay according to any one of claims 1 to 6, wherein an extruded shape of a 6000 series or 7000 series aluminum alloy is extruded, subjected to a friction stir treatment, and then subjected to an artificial aging treatment. . After extruding a 6000 or 7000 series aluminum alloy extruded shape and subjecting it to friction stir processing, it is fixed to a bumper beam made of a 6000 or 7000 series aluminum alloy extruded shape and subjected to artificial aging treatment together with the bumper beam. A method for manufacturing a bumper stay according to any one of claims 1 to 6, wherein

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