WO2008077163A1

WO2008077163A1 - Moulded part and method for producing such a moulded part

Info

Publication number: WO2008077163A1
Application number: PCT/AT2007/000547
Authority: WO
Inventors: Ralf Eckstein; Markus Meidert
Original assignee: Thyssenkrupp Presta Aktiengesellschaft
Priority date: 2006-12-22
Filing date: 2007-12-05
Publication date: 2008-07-03
Also published as: EP2097187B1; DE102006062242B4; EP2097187A1; ATE538882T1; PL2097187T3; ES2380012T3; DE102006062242A1

Abstract

The invention relates to a moulded part which is hollow at least in sections and comprises a wall (3), in its hollow region, which at least partially surrounds the cavity (49) of the moulded part and comprises a moulded element (6, 40, 41, 42) in at least one area (5). According to the invention, a local weakening (7-12) and/or holding edge are formed in the wall (3), at a distance from the moulded element (6, 40, 41, 42), in the direction of a main deformation line (52) of the moulded part, said weakening and/or holding edge extending at an angle to the main deformation line (52), at least over part of the extension of the moulded element (6, 40, 41, 42) and adjacently thereto. The invention also relates to a method for producing such a moulded part.

Description

FORM PART AND METHOD FOR PRODUCING SUCH A FORM PART

The invention relates to a molded part according to the preamble of claim 1 and a method for producing a molded part according to the preamble of claim 12.

Such moldings are for example machine parts with contours for transmitting force and movement such as cams, ramps with gradients in the axial direction and in the circumferential direction, switching scenes in the form of openings, switching scenes in the form of depressions, meandering structures and gears. If high strength and accuracy requirements apply to such molded parts, their production is very complicated and expensive. For example, in racks, especially for steering systems of motor vehicles, it is important to obtain the most accurate tooth geometry and high tooth strength. In the prior art, there are a number of methods by which racks are produced by forming or machining processes and corresponding post-processing steps. But such racks often have a high weight and correspondingly high material costs.

In JP 11-180318 A, a method for producing a hollow rack made of a flat sheet is presented, in which in a first step, the sheet is bent into a U-shape, wherein the connecting portion between the two U-legs is semicircular. Subsequently, the toothing is pressed into the apex of the arc of the connecting portion and bent the legs to a closed tube profile.

In an alternative embodiment of JP 11-180318 A, the toothing is first pressed into the flat sheet metal. Subsequently, the areas of the sheet are bent next to the teeth to a closed tube.

In both embodiments, the legs of the U-profile are unequal in length and it is the longer of the two legs transformed to form the closed pipe profile. However, in both embodiments, the tooth shape is not very accurate to produce. The bending operations bring tension in the area of the teeth, which leads to a distortion of the teeth. This also changes the uneven leg length only a little.

In the US 6,845,560 B2, the production of a rack made of a flat sheet is also presented. Here, the sheet is bent to a U-profile with two side legs and a connector. In the connector, an area is formed flat and on both sides thereafter, two areas are semicircular. In addition, this semicircular area is adjacent to the flat area with increasing distance from the flat area with a rising course reshaped. Following this transformation, the teeth are pressed into the planar area in a second step and, in a third step, the side legs are bent together to form a tube.

Also in this example, stresses are introduced into the toothing in the subsequent subsequent to the pressing of the toothing deformation, which lead to a delay. The special rising shape of the semi-circular connecting portion adjacent to the flat area, in which the teeth are then pressed, is not sufficient to avoid such stresses.

In a forming stresses are introduced into the starting workpiece by forming tools or active media, which lead to corresponding changes in shape. As a rule, there is a multiaxial stress state in the workpiece, resulting in correspondingly multi-axial shape changes. According to "Umformtechnik, Handbuch für Industrie und Wissenschaft", edited by Kurt Lange, Springer Verlag 1984, major changes in form can be defined for such changes in shape, which in the case of a flat shape change run in two directions (Vol. 1, page 144) Sheet metal is assumed to be a (piecewise) plane strain state for simplicity, resulting in essentially two main strain directions, one inside the sheet metal piece In the case of bending, the shape of the piece of sheet metal is plastically deformed along these major changes in shape ptformänderungs line be designated.

A bending line of the molding is defined as extending from a point of the molding along a maximum of the bend of the molding. In the case of bending deformation of the molding, it corresponds to the neutral fiber in cross-section at right angles to the axis about which the molding is bent.

The object of the invention is to provide a formed from a flat piece of sheet metal by forming the flat piece of sheet metal molded part of the type mentioned, which has a very precise form of the at least one element element at a low production cost. Next, a method for producing a molded part of the aforementioned type is to be provided in which a very high precision of the element is already achieved after the forming.

The object is achieved by a molded part with the features of claim 1 and by the method for producing a molded part having the features of claim 12. In the dependent claims 2 to 11 are advantageous developments of inventive molding or in the dependent claims 13 to 17 of the manufacturing method according to the invention for the molding presented.

Core idea of the invention is that can be influenced by appropriately introduced into the sheet weakening and / or holding edges introduced by the subsequent forming steps in the sheet tension distribution. Thus, for example, stresses, in particular bending stresses over transversely to a main strain curve line, such as a bending line, extending weakenings, such as beads or milled grooves, transmitted only to a small extent. At least the majority of the tension is due to a deformation at the

Weakened point degraded. At edges of the material flow is hindered by the contact with the tool. Accordingly, a tension introduced on one side of the retaining edge with the resulting deformation can only be transmitted to a lesser extent to the other side of the retaining edge.

It will be appreciated that the main strain-change line is selected along which the strain would be transmitted during the subsequent forming steps into the portion in which the forming element is disposed.

In an arrangement of such a weakening point and / or holding edge on an edge of a portion of the sheet metal piece to be formed is therefore only a small part of the stresses in a subsequent transformation of adjacent to the subregion, lying on the other side of the weakening or holding edge portion of the sheet metal piece be introduced into the workpiece, introduced into this sub-area. As a result, it is largely prevented that in a closely toleranced form element, for example a surface contour which has been previously introduced into the sub-area, additional stresses and corresponding shape changes by the subsequent deformation of the delimited by the at least one weakening and / or holding edge of the portion of the sheet be effected.

It should be noted that such precisely shaped form elements also in the case of subsequent post-processing, for. B. grinding operation are beneficial.

The partial region having the shaped element thus represents a region which is as uninfluenced as possible by the influence of subsequent transformations. At least the partial region corresponds in its extent to the expansion of the formula element.

It is preferred if not only at least one but all existing weakenings and / or holding edges are spaced from the toothing, ie have a distance greater than 0 (relative to the circumferential direction). There is then no weakening and / or holding edge present, which is arranged without distance to the toothing or within this or below this (in an arrangement on the opposite inner surface of the wall of the workpiece). The shaped element can be, for example, a surface contour introduced into the wall of the molded part within the partial area or a non-continuous or continuous recess introduced into the wall of the molded part in the partial area or can be formed by a plurality of such recesses.

In an advantageous embodiment of the invention, viewed in the direction of a main deformation line, for example a bending line, seen in front of and behind the partial area or the shaped element, ie in cross section parallel to the main strain line, for example a bending line, seen on both sides of the partial area or of the formula element in each case at least one weakening and / or holding edge. For example, exactly one weakening or holding edge could be provided on each side of the subregion.

For the arrangement and design of such weakening points, the subsequently planned forming operations are advantageously taken into account. For this purpose, numerical simulations (FEM simulations) can be used in which the voltage profiles in the component are simulated and thus the correct arrangement and design of the weakening points can be determined. In principle, the weakening points are to be designed in such a way that the stresses introduced outside the subregion, in particular bending stresses, can be dissipated at the weakened point. This means that as a rule the weakened areas partially or completely delimit a partial area to be protected.

If additional shoulders or edges are introduced into the workpiece as a result of the formation of the weakenings, the material flow is greatly reduced by the installation of the corresponding shoulders or edges on the tool. The weakenings in this case also form holding edges at the same time. This further reduces an introduction of stresses into the subarea that is delimited by the weakenings. In a further development of the invention, therefore, at least one retaining edge is designed as a weakening.

It would also be conceivable and possible, for example, to form retaining edges which do not simultaneously represent weakening. Weakening may be advantageous over retaining edges, inter alia, in that contact with the tool at the point of weakening during forming is not required to avoid unwanted deformations in the portion having the feature. In the case of a retaining edge, a tool contact is required.

The at least one retaining edge is thus used to influence stresses which occur in processes required for the production of the rack. A molded part according to the invention may, for example, be a machine part with a molding element arranged in at least one partial area for the purpose of transmitting force and / or movement, wherein the molding element may be, for. As a cam, ramp with slope in the axial direction and / or in the circumferential direction, a shift gate in the form of a non-continuous or continuous recess (ie in the form of a depression or breakthrough), a meandering structure or a toothing can be. Furthermore, it would be conceivable and possible, for example, that the mold element is a surface structure with an optical effect, such. B. in a Fresnel lens.

After the introduction of the at least one formula element in the subregion of

Molded part is at least one further deformation of the molded part, which represents or includes in particular a bend of the molded part carried out, wherein the respective introduced weakening and / or holding edge counteracts a further uncontrolled deformation of the molded part in the partial area. In this case, the partial region in which the molded element is located is preferably on both sides of at least one weakening and / or retaining edge, with reference to the main deformation line, for example a bending line, formed during the deformation, in particular bending operation, which takes place to form the molded part demarcated, this weakening or holding edge transverse, preferably orthogonal, to the main strain line, such as a bending line runs.

In one embodiment of the invention, prior to the introduction of the at least one molding element, at least one preliminary forming of the piece of sheet metal, which in particular constitutes or comprises a bending of the molding, has already been carried out.

The weakenings and / or holding edges are preferably formed linear. The linear course can be straight. Also, a curvatures and / or angularly extending sections having line-shaped course is conceivable and possible. Furthermore, interruptions of the weakenings and / or holding edges in the linear course are possible.

The solution according to the invention is used with advantage in cases in which the molding element to be introduced into the sub-area is restricted because of a restricted area

Accessibility, not fully held until the finished formation of the component between the corresponding tool engraving of a top and bottom tool.

In the following, the invention will be explained by way of example with reference to schematic figures. The figures illustrate: Figure 1 shows a first embodiment of a molded part according to the invention, which is in the form of a rack;

Figure 2 shows the starting workpiece, the flat sheet metal blank, for the production of the rack;

Figure 3 shows a first forming stage for forming the rack, shown in cross section; Figure 4 shows a second forming stage for forming the rack, shown in cross section;

Figure 5 shows a possible third forming stage for the production of the rack, shown in cross section;

Figure 6 shows an embodiment of the finished formed rack in the tool, according to the figure 1, shown in cross section; Figure 7 shows the semi-finished rack, according to the forming step corresponding to Figure 3 in isometric view;

Figure 8, the semi-finished rack after the impressing of the teeth and the

Weakenings, corresponding to the figure 4 in side view;

Figure 9 shows an embodiment of the rack according to the invention, corresponding to the figure 1 in longitudinal section;

Figure 10 shows a detail of the rack according to the invention, according to the

Embodiment of Figure 1 in plan view of the toothed side of the rack;

Figure 11, the semi-finished rack, according to the forming step accordingly

FIG. 4 is an isometric view; Figure 12 section Z of Figure 6;

Figure 13 shows a second embodiment of a molding according to the invention, which in

Form of a cam contour having hollow rod is formed, in isometric view;

Figure 14 shows a third embodiment of a molded part according to the invention, which is in the form of a hollow rod with a sliding recess, in isometric

View;

Figure 15 shows a fourth embodiment of a molding according to the invention, in

Cross section, together with a forming tool shown schematically for performing a forming step of this molding.

All figures are only illustrative of the invention. In particular, the

Tool geometries and / or the size ratios shown only schematically.

For better clarity, the tools in the figures 5, 6 and 15 are moved apart and the sections are not partially shown as hatching.

FIG. 1 shows a section of an embodiment of a molded part according to the invention in the form of a rack 1 in an isometric view. The rack extends in a longitudinal direction 39 and comprises the wall 3, which surrounds the longitudinal axis 2 of the rack 1 with the formation of the cavity 49. In a partial region 5, a toothing 6 with the teeth 13 is embossed as a molded element. The subregion 5 expands at least over the region of the toothing 6. Based on the tangential direction or circumferential direction 4 of the portion 5 is through Weakenings 7, 8, 9, 10, 11, 12 delimited extending in the circumferential direction by a distance 24 or 24 'spaced on both sides next to the toothing 6. These weakenings 7 - 12 extend in the longitudinal direction 39 of the rack, that is parallel to the longitudinal axis 2, and have a length 25 which corresponds approximately to the length of the toothed portion 6. As can be clearly seen in the sectional representation (FIGS. 6, 12), the wall thickness of the wall 3 at the weakening points 7, 8, 9, 10, 11, 12 is made thinner in relation to the initial wall thickness or the wall thickness in the surroundings. In the exemplary embodiment, the teeth run in a straight line and at an angle of α = 90 ° both to the longitudinal axis 2 and to the direction of the weakening points 7, 8, 9, 10, 11, 12 (see FIG. 10). However, the invention also includes other types of gears in which, for example, the angle of the tooth direction with respect to the longitudinal direction 2 is in the range between 30 and 90 °. In this case, the teeth can be configured as desired, for example as a helical toothing or as a toothing with variable pitch.

The circumferential direction 4 corresponds to the direction of the course of the bending line of the toothed rack 1 (see Fig. 6), which here corresponds to the main shape change line 52.

In the illustrated embodiment, weakenings 7-12 are formed on the outer surface 15 and on the inner surface 14. It is also conceivable and possible to provide weakenings only on the outer surface 15 or only on the inner surface 14 of the wall 3.

In FIGS. 9 and 10, the embodiment of the toothed rack 1 according to the invention is illustrated in longitudinal section (FIG. 9) and in a plan view of the toothing (FIG. 10). With particular reference to FIGS. 9 and 10, it can be seen that, in the example, the subregion 5 in the longitudinal direction 2 is additionally delimited by the holding edges 37, and arches 38, which also serve as holding edges. As can be seen in the example, the delimitation by the weakening points and / or holding edges does not have to take place without interruption. It is readily conceivable and possible to provide gaps in the portions of the weakenings and / or retaining edges. The delimitation of the portion 5, in which the toothing 6 is introduced, increases the quality in the longitudinal direction, but is not necessarily required because of the direction of the toothing and the forming steps necessary in the manufacturing process, since only a small proportion of stresses in the sub-range 5 is introduced from outside.

Due to the bending of the workpiece transversely to the longitudinal direction 2, the majority of the stresses in the circumferential direction 4 are introduced into the workpiece. Therefore, the weakenings 7 - 12, which delimit the partial region 5 with respect to the circumferential direction 4, are provided in order to transmit the stresses in the Part 5 to reduce. It is preferable in this case if the length 25 of the weakenings 7 - 12 corresponds at least to the length of the partial region 5, that is to say at least the length of the toothing 6, measured in the longitudinal direction 2. It is quite possible to form the weakenings 7, 8, 9, 10, 11, 12 with interruptions along their length. Preferably, the Weakening is formed as a press-fitted continuous groove, wherein its length 25 corresponds to the length of the partial region 5 or the toothing 6 in the longitudinal direction 2 or projects beyond this on both sides by up to 5%. The depth 33 of the embossed groove is in the preferred case 1/4 to 1/3 of the wall thickness of the wall 3 (see also Fig. 12). In the event that both on the inner surface 14 and on the outer surface 15 of the

Wall 3 indentations are provided as a weakening, the depth of the groove can be further reduced. The depth 33 is then preferably at least 1/6 of the wall thickness of the wall 3. embossing depths that are greater than half the wall thickness, should be avoided. Alternatively, the use of iHaltekanten is also conceivable and possible on these longitudinal sides of the portion 5, wherein it should be noted that the embossed grooves shown in the example already act in addition to the effect of weakening as a holding edge when the grooves in the subsequent forming in contact with the Stand tool.

The distance 24, 24 'of the center lines of the weakenings and / or holding edges 7, 8, 9, 10, 11, 12 from the outlet 32 of the toothing 6 in the circumferential direction 4 amounts to at least 1/3 of the wall thickness of the wall 3 in the preferred part. In the event that two parallel weakenings and / or holding edges 7, 8, 9, 10 are provided on each side of the toothing in the outer surface 15 of the wall 3, the distance 24 is from the tooth outlet 32 to the first weakening and / or holding edge in Circumferential direction 4 in the preferred case approximately in the range of 1/3 of the amount, the wall thickness of the wall 3 to the entire amount of the wall thickness of the wall 3. The distance 24 'from the tooth outlet 32 to the second weakening and / or holding edge in the circumferential direction 4 is located in the preferred case approximately in the range of 2/3 of the amount of wall thickness of the wall 3 to twice the wall thickness of the wall 3. If in addition to a further weakening 11, 12 on the inner surface 14 of the wall 3 are provided on both sides of the toothing, it is preferably arranged in the circumferential direction 4 between the two externally arranged weakenings and / or holding edges 7, 8, 9, 10.

Depending on the wall thickness of the wall 3 and the forming steps, the number of weakening points and / or holding edges and their location on the inner surface 14 or outer surface 15, the wall 3 set. An arrangement of retaining edges is preferred only on the outer surface 15 of the wall 3, since it is simply possible only during the first forming stages, a tool contact between the retaining edge and

Tool engraving to achieve. Depending on the position of the weld seam 35 in the circumferential direction, it may even be sufficient to provide only a single weakening and / or holding edge. Since in ^' rule, however, the rack must withstand very high loads, the wall thickness of the wall 3 will usually have to be relatively thick. Accordingly, three weakenings, in each case two on the outer surface 15 and one on the inner surface 14 of the wall 3, are preferably introduced into the workpiece on each side of the subregion. The two weakenings 7, 8 on the outer surface 15, which are arranged closest to the partial area, are at the same time designed as holding edges. The Geometrical design of the weakenings is preferably carried out so that a removal of the workpiece after forming the toothing is not hindered by undercuts.

Weakening and / or Haitekanten that delimit the portion 5 in the circumferential direction 4, could also extend at an angle to the longitudinal direction 39, preferably at an angle of less than 45 ° to the longitudinal direction 39th

The sequence of processes for producing the rack from a flat sheet 16 is exemplified in its main steps in FIGS. 2, 3, 4, 5 and 6.

In a first step (FIG. 3), the flat sheet metal in a forming tool, consisting of punch 17 and die 18, in a half-shell-shaped or U-shaped form, comprising two legs 19, 20 with two ends 21, 22 and a connecting portion 23 which is arranged between the two legs 19, 20, reshaped. In the preferred case, the two legs 19, 20 are not parallel to each other, but in the direction away from the connecting portion 23 is openably aligned. The wall 3 of the workpiece comprises after forming a concave surface (inner surface 14) and a convex surface (= outer surface 15). To improve the formation of a circular end shape of the rack 1, the end pieces of the two legs 19, 20 are slightly bent after the forming, such that the planes on which the two leg ends 20, 21 are located within of the connecting portion 23 and of the Cut legs 19, 20 partially enclosed space. It is irrelevant whether the bending of the two leg ends 20, 21 in a previous forming step or integrated in this first step, as illustrated in Fig. 3, has taken place. In the figure 7, the workpiece is illustrated after the first forming step in an isometric view. The partial region 5 in which the toothing 6 is introduced in the later forming steps is indicated by the dashed lines.

The orientation of the legs 19, 20 ensures good accessibility of forming tools for subsequent forming operations.

4 illustrates a second and third forming step for introducing the weakenings 7-12 and the toothing 6. In the preferred sequence of the method, the second and third forming steps are combined into a forming step at the same time in a forming tool. In this forming step, in a further forming tool, consisting of punch 26 and die 27, the weakenings 7, 8, 9, 10 on the outer surface of the wall 3, the weakenings 11, 12 on the inside of the wall 3 and the toothing 6 in the Component pressed. The open non-parallel alignment of the two legs 19, 20 facilitates retraction of the punch 26 to the inner surface 14, which on the one hand facilitates the formation of the toothing and on the other hand, the indentation of the weakenings 11, 12 on the inner surface 14 of Wall 3 allows. In particular, the stamp 26 can be moved out of the workpiece after deformation without damaging the inner surface 14 and the leg ends 21, 22. In the die 27, at least the corresponding negative contours for the weakenings and the toothing 6 are formed. In the stamp 26, the negative contours for the weakenings and for the inner surface in the area of

Gearing 6 is formed. The inner surface in the region of the toothing 6 is designed according Umformtechnischen aspects such that the toothing 6 is formed in the best possible quality. The quality standard used here is in particular the shape deviation and the residual stresses in the workpiece. An example of this is the inner contour in the region of the toothing 6, as shown in FIG.

In order to form at least one weakening 11, 12 on the inner surface 14 of the wall 3 (in the exemplary embodiment, there are two weakenings 11, 12), mold elements corresponding to the stamp 26, such as edges, can be provided. At least one of these form elements, preferably all, is arranged in the circumferential direction at a distance from the toothing, so it is not below the same.

In FIG. 11, the formed workpiece, corresponding to the same intermediate stage of the forming sequence, as illustrated in FIG. 4, is illustrated in an isometric view. The weakenings I ₁ 9, limit the portion 5 in which the teeth 6 is introduced.

In the figure 8, the workpiece after the successful second and third forming step is shown in side view

It is conceivable and possible to disassemble the second and third forming steps combined in the exemplary embodiment into two or more substeps in which first the weakenings and then the toothing are formed. Alternatively, first the toothing and then the weakening can be introduced into the workpiece. It is also conceivable and possible to introduce some of the weakenings in a first step and then to introduce the toothing and subsequently the remaining weakenings into the workpiece. Alternatively, fewer weakenings can be introduced into the workpiece. The weakenings can also be made in other ways than pressing. For example, the weakenings may be introduced by a rolling or rolling process.

In the next forming step (FIG. 5), the two legs 19, 20 are closed further. For this purpose, the workpiece between the forming tools 29, 30 is inserted, which are closed according to the deformation. It is important that the

Upper die 29 has at least the negative contour of the toothing. In the course of, deformation takes place a facilitated bending along the fold lines 34, which are formed by the weakenings I ₁ 8, 9, 10, 11, 12 in the wall 3 of the workpiece. The Forming stresses that lead to the deformation of the two legs can cause a plastic deformation in this way only to a very small extent or not at all in the area of the toothing 6. Small remnants of the forming stresses are supported by the friction in the forming tool 29, which carries the negative contour of the toothing. As a result, a further deformation of the toothing can be largely avoided.

FIG. 6 illustrates the last forming step in which the two legs 19, 20 are formed into the final shape of the rack 1. After reshaping the two leg ends 21, 22, apart from a possible small elastic springback, in contact with each other, which is almost full-surface by the preferably formed in the first forming step bending. Subsequently, the leg ends 21, 22, preferably welding technology, are connected to each other (not shown here). In addition to the merging of the two leg ends 21, 22 takes place in the last forming step, the final formation of the two legs 19, 20 in a circular section shape. In this step as well, the fold lines 34 formed by the weakenings reduce the penetration of the deformation stresses into the region of the toothing. Also in this step, the negative contour of the toothing is formed in the upper die 31. Moreover, in the upper die 31 and the lower die 30, the negative contour of the finished rack is substantially formed. The restriction essentially relates to a possible deviation from the final contour for the provision of any existing springback and / or appropriate material allowances for subsequent mechanical processing of the rack.

It is obvious that in this bending a tool contact on the inner surface 14 of the wall 3 of the rack 1 in the region of the toothing is no longer easily possible and not performed in the embodiment shown.

As shown in the example, the direction away from the longitudinal axis 2 surface of the toothing 6 during the following on the introduction of the toothing 6 to the bending of the ends 21, 22 of the side legs 19, 20 forming steps in the Werkzeuggravuran. However, it may be necessary for reasons of production sequence not to maintain this tool contact in all subsequent forming stages. However, this is associated with disadvantages and therefore this process sequence should be avoided as much as possible, even if it is included in the invention.

It is obvious that the two forming steps illustrated in FIGS. 5 and 6 can be combined into a single forming step. This would then be the fourth forming step or the third forming step, if said second and third forming step are combined as mentioned in a single forming step. The division or merging of the above-described forming steps is carried out according to the methods of method planning known to those skilled in the art. It is always the goal to combine as many forming steps as possible and to perform them in one process step in one tool.

An example of a method according to the invention is characterized in that it comprises at least the following steps:

o in a first manufacturing step, the flat sheet in a first forming tool 17, 18 in a half-shell shape or U-shape, comprising two legs 19, 20 with two ends 21, 22, the ends 21, 22 opposite each other by a connecting portion 23 with each other o, in a second forming step, one or more weakenings 7, 8, 9, 10, 11, 12 and / or holding edges, in the tangential direction 4 of the portion 5 of the wall 3, which are arranged in a region of the connecting portion 23 is, spaced, in

Longitudinal direction 2 at least along a portion of the length 25 of the portion 5 running, are formed, o in a third forming step in the portion 5, the teeth 6 is pressed and then o in one or more subsequent forming steps the ends 21, 22 of the two legs 19, 20 are bent together to form a cavity extending in the direction of the longitudinal axis.

Another example of a method according to the invention is characterized in that it comprises at least the following steps:

o in a first manufacturing step, the flat sheet in a first forming tool 17, 18 in a half-shell shape or U-shape, comprising two legs 19, 20 with two ends 21, 22, the ends 21, 22 opposite each other by a connecting portion 23 with each other are connected, is formed, o in a second forming step in the portion 5, the toothing 6 is pressed and o in a third forming step, one or more weakenings 7, 8, 9, 10, 11, 12, and / or holding edges in the tangential direction from the portion of the wall 3, which is arranged in a region of the connecting portion 23, spaced, in

Lengthwise 2 at least along a portion of the length 25 of the portion 5 extending, is formed and then o in one or more subsequent forming steps, the ends 21, 22 of the two legs 19, 20 are bent together to form a longitudinal axis extending cavity. The formation of the teeth and the generation of the weakenings or holding edges can be done in this embodiment together in a single forming step in a forming tool.

o in a first step, one or more weakenings 7, 8, 9, 10, 11, 12 and / or

Holding edges that limit a portion 5 of the flat sheet 16 are introduced, o in a further manufacturing step, the flat sheet in a first

Forming tool 17, 18 in a half-shell shape or U-shape, comprising two legs 19, 20 with two ends 21, 22, which are the ends 21, 22 connected to each other by a connecting portion 23, is reformed, o in a further forming step that before the formation of the U-shape, after the

Forming the U-shape or carried out together with the formation of the U-shape, in the portion 5, the teeth 6 is pressed and then o in one or more subsequent forming steps, the ends 21, 22 of the two legs 19, 20 to form a in Direction of the longitudinal axis extending cavity are bent together.

The weakenings are formed as embossed grooves in the examples illustrated in the figures. It is alternatively conceivable and possible to interpret the weakenings as corrugations which may be rolled or pressed. Likewise, the weakenings and / or holding edges can be produced by a machining process, for example milling. However, it is also conceivable and possible to interpret the weakenings as breakthroughs. Further, areas of the workpiece may also be annealed to achieve such weakening.

In an alternative embodiment of the invention, the weakenings and / or holding edges are already introduced into the starting workpiece, the flat plate 16. This can be done in a simple manner by a stamping operation simultaneously with the cutting of the sheet metal pieces 16 of a coil. It is even conceivable and possible, the weakening and / or holding edges already during rolling of the metal strip from which the sheet metal pieces 16 are punched to introduce. In the course of the remaining steps of the procedure then no additional weakening and / or holding edges need to be introduced accordingly.

A rack according to the invention may be formed hollow overall or it may comprise a hollow portion, as shown for example in Fig. 1, on which one side or both sides further, for example, massive parts are attached, for. B. are welded. The hollow portion of the toothing may, in addition to the substantially circular cross-sectional contour shown (apart from the toothing area), also have other cross-sectional contours, for example a square or triangular cross-sectional contour.

It would also be conceivable and possible to provide several sections 5 on the rack 1, which are formed at different positions in the circumferential direction 4 and / or at different positions in the longitudinal direction 39 in the wall 3 of the rack 1, wherein the portions 5 according to the invention by Weakening and / or holding edges are delimited. In this case, the various sections 5 teeth 6 and / or other form elements, such as functional surfaces for the storage of the rack in the pressure piece of the steering system, have.

A second embodiment of the invention is shown in FIG. The molding is here in the form of an at least partially hollow rod 46 which has a cam contour 40. The rod 46 in turn extends in a longitudinal direction 39 and has a wall 3, which surrounds the longitudinal axis 2 of the rod 46 in cross-section annular view. The circumferential direction 4 again corresponds to the direction of the course of the main shape change line, here in the example of the bending line, the rod 46th

The cam contour 40 is formed in a portion 5 of the rod 46 on its outer surface 15. Of the cam contour 40, for example, a pressed-on this by spring force, not shown in Figure 13 part at a take place in the longitudinal direction 39 of the rod displacement of the rod 46 are displaced (in the direction perpendicular to the longitudinal axis 2).

Seen in the circumferential direction 4 are in front of and behind the cam contour 40 again in the longitudinal direction 39 extending weakenings, of which in Figure 13, only the arranged on one side of the cam contour 40 weakenings 7, 9 are visible. Furthermore, in relation to the longitudinal direction 39, weakenings can again be arranged in front of and behind the cam contour 40 which extend transversely to the longitudinal direction 39 and of which only the weakening 37 is visible in FIG.

On the inner surface of the wall 3 again weakenings can also be arranged.

The weakenings and instead or additionally providable holding edges can have all the configurations and arrangements already described in connection with the first embodiment. The second embodiment shown schematically in Figure 13 thus differs from the first embodiment only by the nature of the arranged in the portion 5 element form.

A third embodiment of the invention is shown schematically in Figure 14, which again differs from the first embodiment only by the nature of the introduced formula element. This is formed in the third embodiment of a recess formed in the form of a recess 41. This serves to cooperate with a not shown in Figure 14, engaging in the sliding recess 41 part which is actuated during the displacement of the rod 47 in the longitudinal direction 39.

The sliding recess 41 could also be formed continuously through the wall 3, thus forming an opening in the wall 3.

A fourth embodiment of the invention is shown schematically in cross section in FIG. The molding 48 in turn has an internal cavity 49 which, in contrast to the previously described embodiments, is not completely sealed off from the exterior space, but instead has an opening between the ends of the legs 50, 51 of the molding 48. Also in the direction perpendicular to the image plane of the cavity 49 may be open at the ends of the molding 48.

In a partial region 5 of the molded part 48, a surface contour 42 is formed on the outer surface 15 of the wall 49 partially surrounding the cavity. As seen in FIG. 15 through the molded part 48, weakenings 7, 8 of the wall 3 are arranged on both sides next to the surface contour 42. These extend at right angles to the main deformation line 52, here the bending line, of the molding 48. The linear weakenings 7, 8 could in turn also include angles other than 90 ° with respect to the bending line 52, wherein the angle enclosed by the bending line 52 preferably in the range between 45 and 135 ° lie.

In the direction perpendicular to the sectional plane of FIG. 15, weakenings may also be arranged in front of and behind the surface contour 42, which weakenings are parallel to the bending line 52, for example.

FIG. 15 shows, together with the molded part 48, schematically a tool with which the last forming step has been carried out and which comprises the tool halves 43, 45. The engraving of the tool half 43 contains the negative mold of the surface contour 42. Furthermore, the tool half 43 has projections 53, 54, which engage in groove-shaped weakenings 7, 8. The weakenings 7, 8 thus represent simultaneously holding edges. The tool half 45 has a support punch 44, from which during the forming, the molding 48 is supported on its inner surface 14 over a part of the portion 5. Furthermore, the tool half 45 comprises bending lugs 55, 56 for bending the legs 50, 51 when the tool halves 43, 45 are brought together.

In the figure 15 an application of the solution according to the invention is illustrated, in which a first portion 57 of the mold element 42 is held until the finished formation of the molding 48 between the engraving of an upper tool half 43 and the Abstützstempel 44 a lower mold half 45. However, an edge region 58 of the molding element 42 can not be held on the inner surface 14 of the molding element 48 by the Abstützstempel because of the unfavorable accessibility. The inventive solution, however, the molding element 42 is still formed in high quality.

Instead of the weakenings 7, 8 or in addition to these weakenings could also be present on the inner surface 14 of the molding 48. Also, more than two weakenings 7, 8 could be arranged on the outer and / or inner surface 15, 14. Instead of weakening or in addition to these pure holding edges could be provided, of which the wall 3 is not weakened.

Furthermore, the solution according to the invention is applicable to components with a very high aspect ratio in the region of the formula element.

It is obvious that the solution according to the invention is also applicable to components having a plurality of mold elements.

L e g e to the reference numbers:

1 rack 40 cam contour

2 longitudinal axis 45 41 sliding recess

3 wall 42 surface contour

4 circumferential direction 43 Tool half

5 subarea 44 support punches

6 Gearing 45 Tool half

7 weakening 50 46 rod

8 weakening 47 rod

9 weakening 48 molding

10 weakening 49 cavity

11 weakening 50 thighs

12 weakening 55 51 thighs

13 tooth 52 main shape change line,

14 inner surface bending line

15 outer surface 53 projection

16 flat metal 54 projection

17 Forming tool, punch 60 55 Bending nose

18 forming tool, die 56 bending nose

19 legs 57 first area

20 legs 58 edge area

21 leg end α angle

22 leg end

23 connecting section

24 distance

24 'distance

25 length

26 forming tool, stamp

27 Forming tool, die

28 forming tool

29 forming tool

20 forming tool

31 forming tool

32 tooth outlet

33 embossing depth

34 crease line

35 weld

36 bend line

37 retaining edge

38 sheets

39 longitudinal direction

Claims

Claims:

1. molding, which is hollow at least in sections and in its hollow portion a cavity (49) of the molding at least partially surrounding wall (3), in at least a portion (5) a molding element (6, 40, 41, 42 ), characterized in that at least one local weakening (7 - 12) and / or holding edge formed in the wall (3) in the direction of a main shape change line (52) of the molded part from the mold element (6, 40, 41, 42) spaced which extends at an angle to the main strain-change line (52) at least over part of the extension of the feature (6, 40, 41, 42) adjacent thereto.

2. Molding according to claim 1, characterized in that in a cross-section parallel to the main shape change line (52) seen on either side of the formula element (6, 40,

41, 42) at least one weakening (7, 8) or retaining edge is provided.

3. Molding according to one of the preceding claims, characterized in that at least one weakening (7, 8, 9, 10, 11, 12) and / or holding edge is aligned at right angles to the main shape change line (52).

4. Molding according to one of the preceding claims, characterized in that at least one weakening (7, 8, 9, 10, 11, 12) or retaining edge by pressing on at least one surface (14, 15) of the wall (3) is generated ,

5. Molding according to one of the preceding claims, characterized in that at least one weakening (7, 8, 9, 10, 11, 12) or retaining edge is produced by a rolled bead in the wall (3).

6. Molding according to one of the preceding claims, characterized in that at least one weakening (7, 8, 9, 10, 11, 12) on the inner surface (14) and / or the outer surface (15) of the wall (3) is arranged ,

7. Molding according to claim 6, characterized in that on the outer surface (15) of the wall (3) on both sides of the molding element (6, 40, 41, 42) in each case two weakenings

(7, 8, 9, 10) are arranged.

8. Molding according to one of the preceding claims, characterized in that the shaped element (6, 40, 41, 42) is a surface contour of the wall or a recess in the wall (3).

9. Molding according to one of the preceding claims, characterized in that the molded part extends in a longitudinal direction (39) and the main shape changing line (52) perpendicular to the longitudinal direction (39).

10. Molding according to one of the preceding claims, characterized in that the at least one weakening (7 - 12) and / or holding edge has a linear course.

11. Molding according to one of the preceding claims, characterized in that the main shape change line (52) corresponds to a bending line.

12. A method for producing a hollow portion of a molded part or a hollow molded part from a flat sheet (16), wherein the sheet is formed such that it forms a wall (3) at least partially surrounding the cavity (49) of the molding, which in at least one subregion (5) has a shaped element (6, 40, 41, 42), characterized in that one or more weakenings (7-12) and / or holding edges in the direction of a main shape change line (52 ) are formed spaced apart from the already introduced or still to be introduced mold element (6, 40, 41, 42), which at an angle to the main shape change line (52) over at least part of the extension of the already introduced or still to be introduced element element (6, 40, 41 , 42) extend beside it.

13. The method according to claim 12, characterized in that one or more weakenings (7 -12) and / or holding edges are formed before at least one subsequent forming step, in which the flat sheet (16) in a curved

Form is brought or the already placed in a curved shape sheet is brought into another curved shape.

14. The method according to claim 12 or 13, characterized in that one or more weakenings (7 - 12) and / or holding edges are formed in the planar sheet.

15. The method according to any one of claims 12 to 14, characterized in that during the on the introduction of the molding element (6, 40, 41, 42) subsequent forming steps, the mold element (6, 40, 41, 42) in the die of a forming tool ( 27, 29, 31, 43, 45) is supported at least on the outer surface (15).

16. The method according to any one of claims 12 to 15, characterized in that the flat plate (16) in a first forming tool (17, 18) in a half-shell shape or U-shape, comprising two legs (19, 20) through a connecting portion (23) are connected to each other and each having a remote from the connecting portion end (21, 22) is deformed.

17. The method according to claim 16, characterized in that thereafter at least one further circumferential step is carried out, in which the ends (21, 22) of the two legs (19, 20) brought closer together or brought together and in which the at least one weakening ( 7 - 12) and / or retaining edge is already introduced.