EP0770435B1 - Method for making an axle support - Google Patents

Description

The invention relates to a method for manufacturing an axle beam for motor vehicles by bending and Hydroforming a straight metallic hollow profile.

Construction workpieces such as axle beams of motor vehicles are consistently carried out today in lightweight construction. Such construction workpieces are usually around hollow molded parts made of a straight metallic mostly cylindrical tube are manufactured. The hydroforming process offers for the forming processing of the pipe various possibilities. Here, a cylindrical tube is used as the initial profile under the pressure of a liquid with simultaneous axial Feed movement widened and shaped like a divided hollow tool pressed. Hydroforming is described in "WT Workshop Technology" 79 (1989), pages 210 to 214. Because of its manufacturing technology Advantages is the hydroforming process, especially in the mass production of Construction workpieces, for example for the automotive industry, widespread.

So far, the production of curved axle beams proceeded in such a way that pipes are first pre-bent. Here, the pipes are brought into a shape, which corresponds to the later contour of the axle beam. The bent hollow profile is then hydroformed brought into the final form. This approach, as for example in DE-PS 40 17 072 (state of the art) has generally proven itself.

After the hydroforming process, the axle support is off Contour finished. Now add-on parts welded to the axle beam. In such Attachments can be reinforcements, for example in the form of gusset plates, that of stabilization serve the axle carrier. Such attachments are usually used however for fastening the axle carrier or Definition of other components on the axle support required.

The subsequent attachment of the attachments is cost and labor intensive. In addition to the quantity and on time Providing the attachments is the effort for the high welding specification. Is accordingly rationalization of the manufacturing process is desirable.

JP-A-64053719 also applies a method for Production of a construction workpiece by bending and hydroforming a straight metallic hollow profile the state of the art. Here, first of all, by hydraulic internal pressure bulges in the bending area created. The hollow profile is then used bent by inner mandrels. The use of inner Support arbors is only comparatively simple Component geometries possible.

The invention is based on the prior art Task based on the production of curved axle beams to make it more appropriate and economical and the number of subsequently on the construction workpiece to reduce attachments to be welded on.

The solution to this problem consists in the Claim 1 listed features.

The basic idea of the invention is First, enough material in on the straight starting profile to relocate the zones of forming, creating forming areas be preformed. The creation of the contour of the Subframe is then done by bending and hydroforming Final shaping.

In particular, fastening or reinforcement areas of the axle support can also be hydroformed before the bending process be shaped out of the initial profile.

The method according to the invention thus makes it possible in any case much of the otherwise after the final shaping parts to be welded on to be replaced.

In the manufacture of the axle beam, first of all a straight metallic hollow profile in the form of a tube went out. This is in a multi-part press tool inserted. The press tool is designed so that the targeted preforming on the required areas allows without causing an adverse wall thinning comes in these zones. After closing the The pipe press tool is hydraulic Internal pressure and one engaging at the ends of the tube Axial force loaded.

The axial force is usually rigid on both sides Transfer tools to the pipe. Usually acts these are hydraulically moved pistons with corresponding shaped heads that hold the tube at both ends to lock. An increasing pressure is then built up in the pipe. As soon as this is so high that there is a deformation of the pipe in the area of the pre-deformed areas comes, the ends of the tube are in the axial direction pressed. This process is controlled depending on the internal pressure. Then there is a shift of profile material to the areas to be deformed. This is done area-specific preforming of bulges in the zones of the later bend or the later fastening or reinforcement areas.

The bulging takes place under the influence of a counter pressure, that works specifically in the area to be deformed. This is a precise control of the expansion process possible. The size of the preformed areas is proportional for shortening the length of the hollow profile. To dilute the material or even bursting in the area of To avoid forming bulge, the forehead of the Bulging during the forming process due to the counter pressure supported.

The back pressure can basically be different Generated way. In a convenient way Include counter cylinders in the manufacturing process which are coordinated with the press tool.

An advantage of the method is that with the first Production step first the zones of the forming are prefabricated on a straight pipe. Especially the zones the maximum deformation in which the subsequent The preformed hollow profile is bent, can be targeted to the subsequent plastic forming are prepared.

The bending process takes place under high internal pressure, so that the hydroformed contours remain. Wrinkling or the tube is prevented from being pressed in. By preforming the zones of maximum deformation also becomes the elastic that is otherwise typical for bending Springback avoided. The subsequent one Final shaping is also done by hydraulic internal pressure performed. Here the axle carrier receives its final one Shape. Pushing the ends of the curved construction workpiece not necessary. This is a significant procedural advantage.

The axle beam is used during or after the final shaping calibrated. Basically, it is possible that the final shaping only includes calibration. With the repressing the surface roughness is leveled and the Dimensional accuracy of the construction workpieces increased. In addition, the strength is increased during calibration.

In a further step, the axle beam is attached Mounting openings are provided. The assembly openings can be used for the attachment of additional components as well as for the implementation of other components, such as a brake line be. The assembly openings are made at effective internal pressure. In this way it is avoided that the construction workpiece at the cutting Production of the assembly openings, for example by cutting or punching, deformed.

Before the hydraulic final shaping, the construction workpiece, depending on the design, also be flattened in areas. Here, the preformed Bulges and / or sections of the construction workpiece flattened. This process takes place in the hydroforming tool.

Control devices and hydraulic devices the production system can be used for preforming, used in the bending process as well as in the final shaping will.

The number of attachments to be welded reduced. Necessary fastening or reinforcement areas on the body of the construction workpiece can be made in one piece from the initial profile shape out. The extra effort for that The provision and definition of attachments is minimized or can even depend on the construction workpiece be completely saved.

Advantageous further developments of the method according to the invention can be seen in claims 2 and 3. After that can the construction workpiece both before the bending process as well as after the bending process of a heat treatment undergo by annealing. Here, the through the internal stresses created during the deformation process are reduced. Distortion of the structure due to the deformation can be traced back. The material of the Construction workpiece receives accordingly for the further processing desired properties.

The invention allows the production of a simple and more economical designed axle carrier for motor vehicles. Such a curved axle beam is made from a tube in one piece with integrated fastening or Reinforcement areas made. To do this, first of all Hydroforming carried out with feeding on the straight tube. Here, the zones of maximum deformation preformed. Then the bending of the hydroformed pipe under internal pressure. The preformed Areas are then created according to the respective requirements pressed flat. So fastening or Reinforcement areas are formed. Through hydroforming or calibration, the axle support gets its final shape. If necessary, the axle beam is then attached Provide holes, the punching as described below Internal pressure takes place.

In the case of the axle beam, the number of those to be welded on Add-on parts reduced. As a result, is his Manufacturing more economical. By saving on add-on parts to be welded on subsequently also a weight saving. This in turn affects positive on fuel consumption and pollutant emissions one equipped with the axle carrier according to the invention Motor vehicle from.

Figur 1

in einer schematisierten Ablaufdarstellung den Fertigungsprozeß für einen Achsträger;

Figur 2

in der Ansicht, teilweise im vertikalen Längsschnitt ein Pressenwerkzeug bei der Vorformung;

Figur 3

in der Seitenansicht die Darstellung der Figur 2 entlang der Linie III-III;

Figur 4

einen Teilschritt des Biegevorgangs;

Figur 5

eine weitere Darstellung des Biegevorgangs;

Figur 6

die Darstellung eines Achsträgers bei der Endformung in der Draufsicht;

Figur 7

einen Schnitt durch die Darstellung der Figur 6 entlang der Linie VII-VII.

The invention is described below with reference to the accompanying drawings. In all drawings, corresponding components have the same reference numerals. Show it:

Figure 1

in a schematic flow diagram the manufacturing process for an axle beam;

Figure 2

in the view, partially in vertical longitudinal section, a press tool during preforming;

Figure 3

in the side view the representation of Figure 2 along the line III-III;

Figure 4

a sub-step of the bending process;

Figure 5

another illustration of the bending process;

Figure 6

the representation of an axle beam in the final shaping in plan view;

Figure 7

a section through the representation of Figure 6 along the line VII-VII.

FIG. 1 shows the manufacture of an axle support 1 for a passenger car, based on an initial profile in the form of a straight, round in cross section Tube 2.

The axle support 1 (Figure 1E and Figure 1F) essentially comprises two tubular longitudinal sections 3, which over a middle section 4 are connected to each other. Of the Center section 4 transmits in particular torsion and Bending forces from the longitudinal sections 3 in the central section 4 be directed. In the transitions 5 from the longitudinal sections 3 to the central section 4 are on Axle beam 1 formed areas 6. these can for example also for attaching attachments.

For the manufacture of the axle support 1, the tube 2 is provided in a fixed initial length L _A , which is matched to the dimensions of the axle support 1 or to the forming processes carried out during manufacture (FIG. 1A).

First, bulges 7 are preformed on the tube 2 (Figure 1B). The preforming is done by hydraulic Internal pressure, with an axial pushing at the same time the ends 8 is made. In this way, profile material shifted to the areas 6 'to be preformed. In the example shown, these are zones 7 ', in which also the maximum deformation during the later bending process he follows.

The resultant is not mandatory, but advantageous preformed tube 2 'then a heat treatment subjected to medium annealing. This can result in the Preforming internal stress of the tube 2 'is reduced will.

The axis contour 2 '' is then created by bending (Figure 1C). The tube stands during the bending process 2 'under high internal pressure, so that the hydroformed contour preserved. The bending process can also affect connect a heat treatment.

The hydroforming tool is then used in an intermediate step a flattening made (Figure 1D). Here, the Areas 6 'flattened. In the subsequent Hydraulic final shaping (Figure 1E) receives the axle beam 1 its final contour with the required dimensional accuracy (Calibration). With effective internal pressure further punched the mounting holes 9. So will prevents the contour of the axle beam 1 from being pressed in becomes.

In a final manufacturing step (Figure 1F) a trimming of the corner regions 10 of the axle beam 1 is carried out.

The preforming, as shown schematically in FIG. 1B, is carried out in a press tool 11 (compare Figures 2 and 3). The press tool 11 has two tool halves 12, 13 on. On the two end sides 14, 15 an axial punch 16, 17 is arranged in each case. Furthermore has the press tool 11 in the zones where the bulges are preformed, adapted to this Removal openings 18. Here are counter cylinders 19 arranged, the piston 20 of the contour of the bulges are trained accordingly.

After inserting the tube 2 into the press tool 11 the tool halves 12, 13 are moved together hydraulically. The tube 2 is at both ends 8 by likewise hydraulically moved pistons 21 with correspondingly shaped Heads 22 closed. The tube 2 is then with a Pressurized media. The supply of the print medium takes place via a dashed line in FIG Internal high-pressure line 23, which runs through the pistons 21 is.

In the next phase, an axial on the tube 2 Force exerted by the two acting against each other Axial punch 16, 17 is formed. By the axial forces the heads 22 are pressed into the pipe ends 8 and form-fittingly seal the interior 24. At the same time, the liquid pressure increases within the tube 2. Due to the internal pressure with simultaneous axial Tube 2 gets into a plastic load Condition and begins to bulge. Depends on the internal pressure the pistons 20 of the counter-cylinders are now controlled 19 retracted. This leads to a targeted Material transfer into the expansion openings 18 below simultaneous axial feeding of the pipe ends 8, whereby the desired preformed tube 2 'is formed.

The preformed tube 2 'is then bent. Of the Bending process is shown in Figures 4 and 5. For this purpose, the preformed tube 2 'is used by a bending tool 25 added. The ends 8 are through the adapter 26 closed. Then the tube 2 'with internal pressure acted upon. Grip on the longitudinal sections 3 pivotable tool parts 27 and bend this over the shape contour 28. During the bending process, the Center section 4 fixed by the counter contour 29.

The pre-shaped axis contour 2 '' is after the bending process a hydroforming tool 30 in which the Final shaping is carried out (Figure 6). In the hydroforming tool the areas 6 'are first flattened, whereby the forming areas 6 get their configuration. The axis contour 2 '' is also in the areas 6 ' slightly flattened on the top (see also Figure 7). Subsequently is the axis contour 2 '' by the adapter 31 positively closed. Then hydraulically Final shaping, in which the axle support 1 with the required Dimensional accuracy is calibrated. After that become the assembly openings 9 when the internal pressure acts punched.

List of reference symbols

1

- axle beam

2nd

- Pipe
2 '- preformed tube
2 '' axis contour

3rd

- longitudinal section

4th

- middle section

5

- Crossing

6

- forming area
6 'area of 6

7

- bulge
7 'zone of the max. Reshaping

8th

- end of 2nd

9

- assembly opening

10th

- corner area

11

- press tool

12th

- Tool half

13

- Tool half

14

- end of v. 11

15

- end of v. 11

16

- Axial punch

17th

- Axial punch

18th

- Removal opening

19th

- counter cylinder

20th

- piston from 19th

21

- piston from 16 u. 17th

22

- head of 21

23

- Internal high pressure line

24th

- interior v. 2nd

25th

- bending tool

26

- adapter

27

- tool parts

28

- shape contour

29

- counter contour

30th

- hydroforming tool

31

- adapter

L _A

 - initial length

Claims (3)

1. A method of making an axle bearer (1) for motor vehicles by bending and hydroforming of a straight metal hollow profile (2), characterised by the following steps:

   a) the hollow profile (2) is subjected to a hydraulic internal pressure and to an axial force acting at the ends (8) of the hollow profile (2), with zone-wise controlled preforming of bulges (7) out of the material of the hollow profile (2) and shifting of profile material to the zones (6', 7') required to be deformed, the bulging being effected under the influence of counter-pressure acting in the zone required to be deformed,

   b) bending of the preformed hollow profile (2') under hydraulic internal pressure,

   c) end forming by hydraulic internal pressure, the axle bearer (1) being calibrated during or after the end forming,

   d) production of assembly openings (9) with the internal pressure operative.
2. A method according to claim 1, characterised in that the preformed hollow profile is annealed before bending.
3. A method according to claim 1 or 2, characterised in that the hollow profile is annealed after bending.

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