JP4363107B2 - Tapered tube for hydraulic bulge processing and hydraulic bulge processing products - Google Patents

Description

The present invention, hydraulic bulging taper pipe and hydraulic bulging has been product, i.e. the tapered pipe in the axial direction cross-sectional shape changes, hydraulic bulging taper of varying material strength in the axial direction it relates tubes and easily realizable hydraulic bulging product collapse mode of the automobile high resulting occupant protection with this hydraulic bulging taper tube.

The hydraulic bulge processing has the following features compared to the normal molding method.
a) Since a slightly complicated shape having a different cross-sectional shape in the longitudinal direction can be obtained, it is possible to integrally form components that have been conventionally assembled by welding.

b) Since work hardening is easy to obtain over the entire product, a high-strength product can be obtained even if a soft element tube is used.
c) Since there are few springbacks and the dimensional accuracy of the product is good (the shape freezing property is good), the reworking step can be omitted.

The excellent features as described above have been evaluated, and in recent years, they have been adopted particularly in the manufacturing process of automobile parts.
A general pipe hydraulic bulging process will now be described.
A straight tube (hereinafter referred to as “element tube”) having a uniform circular cross section in the longitudinal direction as a raw material is referred to as (1) bending processing and (2) crushing processing (hereinafter referred to as “preform processing”). .), (3) A product is manufactured by performing a series of processing such as hydraulic bulge processing.

The hydraulic bulging is the final step shown in FIG. 1 4, upper mold 1, into the base pipe S1, which is set in the lower die 2, the working fluid is injected through the injection hole 3, the pressure of the working fluid (Hereinafter referred to as “internal pressure”), in addition to the axial push tools 4 and 5 also serving as a sealing tool, the raw pipe S1 is pushed in from the ends of both pipes in the axial direction (hereinafter referred to as “axial push”). .), To produce products S2 having various cross-sectional shapes. The shaft pushing tools 4 and 5 that also serve as a sealing tool are connected to a hydraulic cylinder (not shown), and the axial position or the shaft pushing force is controlled during bulging.

However, the hydraulic bulge processing described above has the following problems.
That is, even if it is possible to obtain a slightly complicated shape having a different cross-sectional shape in the longitudinal direction, there is a limit to this. Perimeter increase rate = {(peripheral length of the product of the part concerned) / (circumferential length of the raw tube-1)} x 100 (%), product shape required performance, material quality and thickness of the raw tube However, except for the tube end region where the axial pushing is effective, the perimeter increase rate is limited to about 25% at most. Under such constraint conditions, in order to increase the degree of freedom of product shape design and to obtain a product having a more complicated cross-sectional shape, it is necessary to devise a raw pipe shape.

One effective countermeasure against this problem is to use a substantially conical tube (hereinafter referred to as a “taper tube”) instead of a straight tube, making it difficult to form a straight tube. The peripheral length increase rate can be kept low even with respect to other parts, for example, parts whose peripheral length varies greatly along the axial direction.
JP 2001-321842 A

Specifically, Patent Document 1 discloses an example in which a taper tube bulge product is applied to a center pillar reinforcement. In general, the center pillar 6 is a skeleton of an automobile body side is a component shown in FIG. 1 5 (a), has a assembling welded structure of the press-molded product, FIG 5 called reinforcement 7 (b) The reinforcing material as shown in is assembled.

The center pillar 6, as shown in FIG. 1 5 (a), the upper section is small part lower section is large, since the outer peripheral length toward the bottom end gradually changes from the top, the use of the tapered tube as a bulge material Better molding becomes possible. And the following big merit will be acquired by applying the bulge product using a taper pipe to the reinforcement of a center pillar.

1) The conventional welded part can be omitted, and the reinforcement has a closed cross-sectional structure, which improves the rigidity of the entire part.
2) The material is work hardened by bulging deformation during bulge processing, and high strength is obtained.
3) The bulge product has a small spring back, which improves product accuracy and reduces defects in the assembly process.

  In this example, the reinforce is described, but naturally a taper tube may be used for the center pillar itself. In this case, there is a possibility that the reinforcement can be omitted by using a high-strength material.

  On the other hand, in recent years, automobiles are required to improve safety in a collision. For this purpose, various collision tests and evaluations are performed, and the results are reflected in the design of automobile parts. As a matter of course, not only the strength of the parts is improved, but also from an aspect different from that, an optimum crushing method (hereinafter referred to as “crush mode”) when an impact load is applied to each part is required. There are many cases. In other words, in addition to minimizing the impact energy received by a passenger (hereinafter referred to as “occupant”) when a collision accident actually occurs, a component that realizes a crushing mode of a vehicle with high occupant protection Design is required.

  The center pillar will be described in more detail as an example. Among passenger injuries in automobile collision accidents, side collision is one of the major collision forms following frontal collision. Since the center pillar is a component that is directly connected to ensuring the safety of passengers in the event of a side collision of an automobile, naturally high strength is required. In addition, in the event of a side collision, it bends and enters the car, so a crushing mode that protects the head and neck that are most susceptible to life-related damage is required.

  There are various ways to design the center pillar.For example, the upper part of the center pillar is strengthened to make it difficult to bend, the starting point of the bend is created at the leg, and the overall strength is improved to reduce the amount of deformation that enters the vehicle. There is also the idea of regulating.

However, when designing the crush mode with high passenger protective automobile as described above, the use of hydraulic bulging products using conventional tapered pipe, there is a problem that a small degree of freedom in design. In other words, in order to control the crushing mode, it is possible to change the crushing mode by changing the shape of the product and designing a shape that tends to be the starting point of bending, or by making work hardening uneven in hydraulic bulging. It is conceivable, however, the basic design of the parts, such as space constraints and securing of rigidity, was carried out, and the above-mentioned design was very restrictive.

  Up to now, the center pillar has been described as an example, but for the design of parts for ensuring safety in various types of collisions, if the change in strength distribution can be given in the axial direction, the degree of freedom in design will be expanded. Needless to say, it will provide excellent safety.

The problem to be solved is that the strength characteristic distribution required for the product after the hydraulic bulge processing cannot be obtained freely.

The present invention makes it possible to obtain the strength characteristic distribution required for a product after hydraulic bulge processing more freely than before, and to obtain a hydraulic bulge processed product having an appropriate strength distribution. Strength required for products after hydraulic bulge processing when producing a pipe for hydraulic bulge processing that has a cross-sectional area that changes in the axial direction as a material for bulge processing using a blank material that has been joined in advance. Based on the characteristic distribution, the deformation resistance of each of the at least two types of plates is selected, and the set position of the blank material joined in advance to the at least two types of plates at the time of hydraulic bulge processing is selected . the cross-sectional average deformation resistance obtained from at least two percentage plate occupied by each in the axial direction perpendicular to the cross section of the product, the most major of which is adapted continuously changed in the axial direction Laid To.

According to the present invention, since the strength change in the axial direction of the hydraulic bulge processed product can be continuously performed, there is an advantage that the degree of freedom in designing a part that realizes a crushing mode of an automobile with high occupant protection is greatly expanded. There is.
Further, there is an advantage that a bulge product having an appropriate strength distribution can be manufactured, and a hydraulic bulge processed product that can easily realize a crushing mode of an automobile with high occupant protection can be provided.

Hydraulic bulging taper pipe of the present invention is a hydraulic bulging taper pipe cross-sectional area in the axial direction of the hydraulic bulging for material changes were prebonded at least two plate-blanks When producing pipes using a material, the respective deformation resistances of the at least two types of plates are selected based on the strength characteristic distribution required for the product after the hydraulic bulge processing, and the at least two types are selected during the hydraulic bulge processing. The cross-sectional average deformation resistance obtained from the ratio of each of the at least two types of plates in the cross-section perpendicular to the axial direction of the product after hydraulic bulge processing is selected . It changes continuously in the axial direction.

In the present invention, the joining lines of at least two types of plates are not abutted at the same position during welding at the time of pipe making, and the distance between the abutting intersections of the joining lines is the same as that of the tapered pipe for hydraulic bulging. If it is 1/2 or more of the radius in the intermediate position of an intersection, it is suitable for the collapse | fold when it crushes not to concentrate on a junction part. Further, when the distance between the intersection points is equal to or larger than the radius at the intermediate position of the intersection point, the crushing mode is further stabilized. In addition, since the said butt | matching is not in the same position, naturally the reliability of welding will be more excellent.

Using said hydraulic bulging taper tube of the present invention, in the hydraulic bulging product obtained by hydraulic bulging, it is possible to manufacture a hydraulic bulging product having an appropriate intensity distribution, An automobile crushing mode with high occupant protection can be easily realized.

Hereinafter, the present invention will be described in detail. Consider a tapered tube 11 for hydraulic bulge processing having a bottom surface radius R0, a top surface radius R1, and a height H as shown in FIG. Here, an axially symmetric tapered tube 11 whose longitudinal axis is perpendicular to the bottom surface is considered.

  A blank (development view) 11a of the taper tube 11 is obtained by removing a sector having a radius L0 from a sector having a radius L of an apex angle θ as shown in FIG. Here, when the L and θ, the length L ′ along the longitudinal direction of the outer peripheral surface of the tapered tube 11 and the length L0 obtained by subtracting L ′ from the L are obtained from the geometric relationship, It becomes like 4.

L = R0 × [1+ {H / (R0−R1)} ² ] ^1/2 .
L0 = R1 × [1+ {H / (R0−R1)} ² ] ^1/2 ... Formula 2
L ′ = {(R0−R1) ² + H ² } ^1/2 Equation 3
θ = 2π / [1+ {H / (R0−R1)} ² ] ^1/2 .

  For simplicity, consider a case where two types of materials having different strengths and thicknesses, that is, the A material 12 and the B material 13 are joined, and the joining line 14 is a straight line. As shown in FIG. 3, the center line 11b of the blank 11a of the taper tube 11 is inclined (greater than 0 ° and less than 90 °) with respect to the perpendicular of the joining line 14, and is punched or cut. The distances from the top surface 11aa on the apex O side of the sector blank 11a, which becomes the top surface when the tapered tube 11 is formed, to the joining line 14 are denoted by H1 and H2, respectively. An arbitrary distance along the generatrix of the tapered tube 11 from the upper surface 11aa is assumed to be X. Now, a circle with a radius (L0 + X) is virtually written from the vertex O, and the angle of the intersection with the joint line 14 is β.

  The average deformation resistance KFM (X) at the distance X along the generatrix of the tapered tube 11 from the upper surface 11aa is as follows when the deformation resistance KFM (A) of the A material 12 and the deformation resistance KFM (B) of the B material 13 are used. It is expressed by Equation 5. In addition, β in Equation 5 is given by Equation 6 below using X. Therefore, by determining H1 and H2, the average deformation resistance KFM (X) at the distance X along the generatrix of the tapered tube 11 is determined. Will be required.

KFM (X) = {1- (β / θ)} · KEM (A) + (β / θ) · KEM (B)
... Formula 5
X = {A (L0 + H1) / (A-tan β)} · (1 + tan ² β) ^1/2 Formula 6
Here, A = (L0 + H2) · sin θ / {(L0 + H2) cos θ− (L0 + H1)}

Here, the effect of the present invention will be described using a taper tube with R1 = 25 mm, R0 = 50 mm, and H = 1000 mm as an example.
For three cases in which H1, H2, KFM (A), and KFM (B) are changed to the values shown in Table 1 below, the average deformation resistance at a distance X along the generatrix of the tapered tube is obtained from Equations 5 to 6. KFM (X) was determined.

  The results are shown in FIG. As is apparent from FIG. 4, the deformation resistance KFM (X) can be changed in the axial direction of the taper tube 11 by changing H1, H2, KFM (A), and KFM (B). In particular, the starting point of the drop in deformation resistance and its gradient could be set relatively freely. That is, the deformation resistance can be changed relatively smoothly and the discontinuity of the deformation resistance can be eliminated, so that the impact characteristics can be easily controlled.

Moreover, it is not restricted to the above-mentioned example, You may change each plate | board thickness of A material and B material. By combining the change in deformation resistance and the change in plate thickness, the control range of the crushing mode is widened. Further, since the deformation resistance distribution of the tapered tube is not axisymmetric, the collapse direction of the product can be controlled by adjusting the set position of the material during the hydraulic bulge processing.

In other words, if the strength characteristic distribution required for the product after hydraulic bulge processing is determined by design, while considering the work hardening and wall thickness distribution corresponding to the pipe expansion distribution in the hydraulic bulge processing,
B) Select the deformation resistance for each of the two types of materials.
B) Change the thickness of each of the two types of materials.
C) Select a blank position (H1, H2).
D) Select the material setting position during hydraulic bulging.
Thus, since the deformation resistance in the axial direction of the product after the hydraulic bulge processing can be appropriately distributed, a design capable of easily realizing a crushing mode of an automobile with high occupant protection is possible.

Further, regarding the hydraulic bulge taper tube 11 of the present invention, the intersection 15 of the welding line 11c of the welding line and the joining line 14 of the two types of materials (A material 12 and B material 13) is regarded as a central point. The upper and lower intersections 15 have a shape close to a T-shape in which three welding lines extend radially from the center point (see FIG. 1). If the distance D between the intersections is equal to or greater than ½ of the radius Rc at the intermediate position c, the crushing mode does not concentrate at the joint and the crushing mode is stabilized.

On the other hand, as shown in FIG. 5B, when the joining line 14 of the two kinds of materials (A material 12 and B material 13) is simply perpendicular to the longitudinal center line 11b of the tapered tube. In addition, the cross-sectional average deformation resistance obtained from the ratio of each of the two types of materials (A material 12 and B material 13) has a portion that changes in the axial direction. If the intersection 15 of the joining line 14 of 11c and two types of materials (A material 12 and B material 13) is regarded as a central point, as shown in FIG. 5A, four welding lines are formed from this central point. From the viewpoint of welding reliability, the example shown in FIG. 1 is excellent because the shape is close to a radially extending + shape (cross shape).

  In the above example, the case where the joining line 14 between the A material 12 and the B material 13 is a straight line has been described, but a curved line as shown in FIG. 6 may be used. In this case, the joint line 14 is more complicated than a straight line, but the distribution of deformation resistance in the axial direction can be more complicated.

  In the process of manufacturing an actual product, different materials may be joined by conventional welding such as TIG welding, electron beam welding, and laser welding, and the welding method itself does not define the present invention. The blank may be produced by a conventional method such as a punching method, a laser cutting method, a combination of shear cutting and punching, or laser cutting, and the manufacturing method of the blank itself does not define the present invention.

  In addition, the taper tube may be manufactured by performing UO pressing and performing welding, or performing C pressing a plurality of times and performing welding in the next step. That is, a predetermined object can be achieved by a method in which the blank is bent and welded. Here, the type of welding in manufacturing the tapered tube is not particularly limited.

  So far, the axially symmetric taper tube whose longitudinal axis is perpendicular to the bottom surface has been described. However, the present invention is not limited to the blank 11a of the taper tube 11 as shown in FIG. Alternatively, as shown in FIG. 7, a tapered tube 11 having a shape in which a part of the busbar is perpendicular to the bottom surface may be used. In this case, as shown in FIG. 8, the blank 11a (development view) has a slightly complicated upper and lower end surface shape. As a matter of course, a tapered tube having an intermediate shape between FIGS. 1 and 7 may be used.

Further, the blank itself may be trapezoidal. In this case, since the blank is surrounded by a straight line, the blank itself can be manufactured only by shear cutting, and the blank can be easily manufactured. However, after the taper tube is manufactured or after the hydraulic bulge forming is performed, the end portion needs to be trimmed.

  For example, when the axisymmetric taper tube 11 whose longitudinal axis is perpendicular to the bottom surface as shown in FIG. 7 is formed from a trapezoidal blank, the sectoral shape of FIG. Considering the blank 11a, the misaligned portion may be trimmed after molding. As for the trapezoidal blank, a virtual fan-shaped blank is considered, and the average deformation resistance KFM (X) at the distance X along the generatrix of the tapered tube 11 from the upper surface is calculated in the same manner as described above using the above Equations 5 to 6. The distribution of deformation resistance can be given by

In the description so far, two types of materials having different mechanical characteristics and plate thicknesses have been described. However, when three or more types of materials are joined, the degree of freedom of design is further expanded. 9-13 has shown the Example which joined three types of raw materials 21-23. In any case, since the deformation resistance in the axial direction of the product after the hydraulic bulge processing can be appropriately distributed, a design capable of easily realizing a crushing mode of an automobile with high occupant protection is possible. In addition, 24 in FIGS. 9-13 shows the joining line | wire of raw materials 21-23.

In this embodiment, the case of a simple taper tube has been mainly described. However, a simple taper tube is used as a material, and a part or the entire length of the tube is subjected to conventional processing such as drawing, swaging, and pipe expansion. As described above, it can be applied to a hydroformed product.

It is explanatory drawing which shows an example of the taper pipe | tube for hydraulic bulge processing of this invention, and is the axis-symmetric taper pipe | tube with the longitudinal axis center perpendicular | vertical to a bottom face using two types of materials from which a mechanical characteristic and board thickness differ. It is explanatory drawing. It is explanatory drawing of the blank used for manufacturing the taper pipe | tube of FIG. It is explanatory drawing at the time of obtaining the blank of FIG. 2 using two types of raw materials from which mechanical characteristics and board thickness differ. It is explanatory drawing showing distribution of the deformation resistance of the taper pipe for hydraulic bulge processing of the present invention. (A) is explanatory drawing of the taper pipe | tube for hydraulic bulge processing of this invention equivalent to only Claim 1, (b) is the hydraulic pressure of (a) using two types of raw materials from which mechanical characteristics and board thickness differ. It is explanatory drawing at the time of obtaining the blank for taper pipes for bulge processing. It is a figure similar to FIG. 3 in case the joining line of two types of raw materials is a curve. It is explanatory drawing of the taper pipe | tube for hydraulic bulge processing of this invention similar to FIG. 1 when a part of bus line is perpendicular | vertical to a bottom face. It is explanatory drawing of the blank used for manufacturing the taper pipe | tube of FIG. It is explanatory drawing at the time of obtaining the blank for the taper pipe | tube for hydraulic bulge processing of this invention using three types of raw materials from which mechanical characteristics and board thickness differ. It is explanatory drawing which shows the other example of FIG. It is explanatory drawing which shows the other example of FIG. It is explanatory drawing at the time of making the upper joining line of FIG. 10 into a curve. It is explanatory drawing at the time of making the upper joining line of FIG. 11 into a curve. It is explanatory drawing of the hydraulic bulge processing process of the conventional straight pipe, (a) is the figure which showed before a process and (b) after completion | finish of a process. (A) is explanatory drawing of a center pillar, (b) is explanatory drawing of the reinforcement assembled | attached to a center pillar.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Tapered tube 11a Blank 11b Center line 11c Join line 12 A material 13 B material 14 Join line 15 Intersection 21 Material 22 Material 23 Material 24 Join line 31 Tube

Claims (3)

A taper tube for hydraulic bulge processing whose cross-sectional area changes in the axial direction, and is required for products after hydraulic bulge processing when pipes are made using a blank material in which at least two kinds of plates are joined in advance. Based on the distribution of strength characteristics, select the deformation resistance of each of the at least two types of plates, select the set position of the blank material joined in advance to the at least two types of plates during hydraulic bulge processing, and after hydraulic bulge processing The hydraulic pressure is characterized in that the cross-sectional average deformation resistance obtained from the ratio of each of the at least two kinds of plates in the cross section perpendicular to the axial direction of the product of the product continuously changes in the axial direction. Tapered tube for bulge processing. The taper pipe for hydraulic bulge processing according to claim 1, wherein the joining lines of the at least two types of plates are not abutted at the same position during welding at the time of pipe making, and the distance between the intersections of the joining lines. hydraulic bulging taper tube, characterized in that but is the radius of 1/2 or more at an intermediate position of the intersection point of the hydraulic bulging taper tube. Using hydraulic bulging taper tube according to claim 1 or 2, hydraulic bulging product obtained by hydraulic bulging.

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