EP1000677B1 - Method for forming a workpiece by application of a high internal pressure - Google Patents

Abstract

The deformation process produces the part from a tube with at least one sector of different wall thickness to the rest of it. An assembled tube (10) is used. An outer tube sector (12) is pushed onto an inner tube (11) of uniform wall thickness in order to create the sector of different wall thickness. The parts are bonded to each other by the molding process.

Description

The present invention relates to a method for producing a component by means of Hydroforming from a tube with at least one section different wall thickness. The present invention also relates to such a tube.

For the hydroforming process (IHU) tubes are usually used as Semi-finished products used. In automotive engineering, dimensioned according to load requirements Components often have a graduated wall thickness. To meet this requirement, the IHU process these tubes are manufactured in graded wall thickness.

DE 196 04 357 A1 describes a method for producing pipes with sections different wall thickness known from an initially flat sheet, in which first a targeted rolling deformation of the sheet in the rolling direction changing sheet thicknesses in certain areas. This results in one targeted partial wall thickness reduction. Then the rolled sheet cut, formed into a tube and joined along the butt edges. A such manufacturing with continuous material in a manufacturing process, however complex and costly.

DE 43 20 656 A1 describes a method for producing a pipe support according to the Internal high pressure forming process known in which a straight tubular body is expanded, the tubular body to be expanded from different Pipe sections having wall thicknesses is welded together. This The production of so-called "tailored tubes" as a welded construction is complex and not without problems for the internal high pressure forming process because of the weld seams.

DE 3610 481 A1 describes a further method for producing pipes with a or several inner wall thickenings known, the thickenings from one cylindrical tube manufactured by cutting processes and / or forming processes are. In a tube with the same wall thickness, the first step is: Machining processes or forming processes externally or externally and internally molded wall thickenings, which are preferably produced in a second step Cold hammers are formed or shaped inwards. This is also the case is a comparatively complex and costly process.

EP 0 733 540 B1 describes a method for producing a hollow profile for a Carrier structure of a motor vehicle by hydraulic expansion of a Output part, an extruded profile being used as the output part, which in Cross-section areas with different wall thicknesses. The wall thickness of the The starting part is chosen so that the hydroforming process manufactured hollow profile has the necessary wall thickness at the required points. The disadvantage of this is that for different hollow profiles with different wall thicknesses separate extruded profiles must be produced as the starting product each time.

Finally, from US-A-4 759 111 is a method for molding a box section frame part from two tubes pushed into each other by expanding the inner one Tube due to hydroforming. The disadvantage of this Procedure a step jump on the surface of the frame part created in the form of a to highlight the so-called discontinuity of the surface of the frame part created, which has to be filled in with complex measures.

The object of the present invention is therefore a method of the above Provide mentioned type, in which the wall thickness gradation with a paragraph-free outer contour can be reached in the simplest possible way.

The object of the invention is also a tube produced by said method

These tasks are characterized by the features of the claims 1 and 6 solved.

The solution is to first use a composite pipe by using an inner tube with a uniform wall thickness to generate the minimum a section of different wall thickness at least one outer pipe section is pushed on and then the assembled pipe High pressure forming process is subjected, so that the parts through the Shaping process are firmly connected to each other, according to the invention at least one end of an outer tube section is designed obliquely in cross section is, so that after the hydroforming process a substantially paragraph-free outer contour of the finished component results. The outer contour then does not need any Post-processing to grind off any paragraphs or joints or in comparable postprocessing.

It is therefore envisaged that the gradation of the wall thickness by pushing To reach pipe sections. This composite semi-finished product is then used in the IHU tool reshaped as usual. During the forming process, the outer diameter of the inner tube to the size of the outer tube so that both parts through the shape can be combined. The length of the resulting part results from the length of the inner tube. The outer pipe section or the outer pipe sections produce the thickening. This ensures that Pressure medium not between the tubes during the hydroforming process arrives and a common reshaping is guaranteed.

Advantageous further developments result from the subclaims. For generation several sections of different wall thickness can have several outer Pipe sections with different diameters on top of each other on the inner pipe be pushed. Instead, the outer pipe sections can be partial can be pushed over each other.

Before and / or after the hydroforming process, one or more can additional connections between the inner tube and the at least one outer Pipe section are produced, for example by laser welding or others Joining techniques. This ensures that the composite semi-finished product in the IHU tool does not slip. These additional connections can, for example, after the forming process are produced in that the resulting component with a or several other components is connected.

Figur 1a

eine schematische teilweise geschnittene Darstellung eines zusammengesetzten Rohres aus einem Innenrohr und einem vollständig auf das Innenrohr aufgeschobenen äußeren Rohrabschnitt;

Figur 1b

ein Bauteil aus einem zusammengesetzten Rohr gemäß Figur 1a nach dem Umformprozeß in schematischer Darstellung;

Figur 2a

ein zusammengesetztes Rohr aus einem Innenrohr und mehreren partiell übereinander geschobenen äußeren Rohrabschnitten;

Figur 2b

ein Bauteil aus einem zusammengesetzten Rohr gemäß Figur 2a nach dem Umformen in schematischer Darstellung.

Embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

Figure 1a

a schematic partially sectioned representation of a composite tube from an inner tube and a completely pushed onto the inner tube outer tube section;

Figure 1b

a component from a composite tube according to Figure 1a after the forming process in a schematic representation;

Figure 2a

a composite tube made of an inner tube and a plurality of partially pushed outer tube sections;

Figure 2b

a component from a composite tube according to Figure 2a after forming in a schematic representation.

In Figure 1a, a composite tube 10 is shown, which consists of an inner tube 11 and an outer tube section 12. The inner tube 11 has the required component length. The outer tube section 12 is in the manner of a sleeve completely pushed over the inner tube 11 so that it has a central region 11b covered and the outer areas 11a remain uncovered. On the outer edges 13 and 14 of the outer tube section 12 are bevels extending inwards 15, 16 provided.

The inner tube 11 and the outer tube section 12 consist for example of a Sheet steel, which is formed into a tube and joined at the butt edges. The Assembled tube 10 is a hydroforming process in the usual way subjected. The resulting component 20 is schematic in FIG. 1b shown. The component 20 consists of outer regions 21, which consist of the Inner tube 11 emerged and correspond to the area 11a designated in FIG. 1a and a thickened region 22, which consists of the region designated by 11b in FIG. 1a of the inner tube and the outer tube section 12 emerged. The outer contour of the Component 20 has no shoulders, since the wall of the former inner tube perfectly to the oblique contour 15, 16 of the outer tube section 12 nestled. In the resulting component 20 are the two parts, namely that Inner tube 11 and the outer tube section 12, firmly together by the shape connected. This connection can be made by establishing additional connection points, e.g. B. can be further solidified by laser welding or by other joining techniques. This Connection points can be made before or after the forming process. There then the connection points made after the forming process, they can are generated that the component 20 with one or more any other Components is connected.

FIG. 2a shows a further exemplary embodiment of a composite tube 30 shown schematically and partially cut. The composite pipe 30 consists of an inner tube 31 and three outer tube sections 32, 33, 34, which are partially are pushed over each other on the inner tube 31, so that an outer region 31a of the Inner tube 31 and the outer free ends 32a, 33a, 33b of the outer tube sections 32, 33, 34 remain uncovered. The outer free ends 32a 33a and 34a of the outer Pipe sections 32, 33, 34 in turn have an inward bevel 32b, 33b, 34b. The composite pipe 30 becomes a common one Subjected to hydroforming process.

The resulting component 40 is schematic and partially sectioned in Figure 2b shown. The component 40 has a thin region 41 which emerges from the outer Region 31a of the inner tube 31 results, as well as gradually thickened regions, namely a single thickened area 42, a double thickened area 43 and one triple thickened area 44. The thickened areas 42, 43, 44 result from the Addition of the wall thicknesses of the different outer ones partially pushed over each other Pipe sections 32, 33, 34. Here too, the design of the outer free ensures Ends 32a, 33a, 34a of the outer tube sections 32, 33, 34 have a shoulder-free contour.

In this case, too, more can be done before or after the forming process Connection points between the inner tube 31 and the outer tube sections 32, 33, 34 are produced. However, these parts are already fixed by the shape connected with each other.

LIST OF REFERENCE NUMBERS

10

pipe

11

inner tube

11a

outer range of 11

11 b

middle range of 11

12

outer pipe section

13

outer end of 12

14

outer end of 12

15

bevel

16

bevel

20

component

21

thin range of 20

22

thickened area of 20

30

pipe

31

inner tube

31 a

outer range of 31

32

outer pipe section

32a

free end of 32

32b

Bevel at 32a

33

outer pipe section

33a

free end of 33

33b

Bevel at 33a

34

outer pipe section

34a

free end of 34

34b

Bevel at 34a

40

component

41

thin area of 40

42

simply thickened area of 40

43

double thickened area of 40

44

triple thickened area of 40

Claims (9)

1. Method of producing a component (20, 40) by means of internal high pressure forming from a tube having at least one section of different wall thickness in such a way that first of all an assembled tube (10, 30) is used by at least one outer tube section (12; 32, 33, 34) being pushed onto an inner tube (11; 31) having a uniform wall thickness for producing the at least one section of different wall thickness and then by the assembled tube being subjected to the internal high pressure forming process, so that the parts (11, 12; 31, 32, 33, 34) are firmly connected to one another by the shaping process, characterized in that at least one end (13, 14; 32a, 33a, 34a) of the at least one outer tube section (12; 32, 33, 34) is designed to be bevelled in cross section, so that an essentially step-free outer contour of the component (20, 40) results after the internal high pressure forming process.
2. Method according to Claim 1, characterized in that the outer tube sections (12, 32, 33, 34) are pushed completely or partly over one another.
3. Method according to Claim 1 or 2, characterized in that, to produce a plurality of sections of different wall thickness, a plurality of outer tube sections (32, 33, 34) having different diameters are pushed over one another onto the inner tube (31).
4. Method according to one of the preceding claims, characterized in that, before and/or after the joining process, one or more additional connections are produced between the inner tube (11; 31) and the at least one outer tube section (12; 32, 33, 34).
5. Method according to Claim 4, characterized in that the one or more additional connections are produced when the component (20, 40) resulting from the internal high pressure forming process is connected to one or more other components.
6. Tube having at least one section of different wall thickness, in particular for use in a method according to one of Claims 1 to 5, the said tube being an assembled tube (10, 30) which has an inner tube (11, 31) having a uniform wall thickness, onto which at least one outer tube section (12; 32, 33, 34) is pushed for producing the at least one section of different wall thickness, characterized in that at least one end (13, 14; 32a, 33a, 34a) of the at least one outer tube section (12; 32, 33, 34) is designed to be bevelled in cross section.
7. Tube according to Claim 6, characterized in that the outer tube sections (12; 32, 33, 34) are pushed completely or partly over one another.
8. Tube according to Claim 6 or 7, characterized in that, to produce a plurality of sections of different wall thickness, a plurality of outer tube sections (32, 33, 34) having different diameters are pushed over one another onto the inner tube (31).
9. Tube according to one of Claims 6 to 8, characterized in that it has one or more additional connections between the inner tube (11, 31) and the at least one tube section (12; 32, 33, 34).

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