EP2097187B1 - Moulded part and method for producing such a moulded part - Google Patents

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

The invention relates to a molded part according to the preamble of claim 1 and to a method for producing a hollow section of a molded part or of a hollow molded part according to the preamble of claim 9.

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 the JP 11-180318 A method is presented for producing a hollow rack from a flat sheet, wherein 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 the 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 is also the production of a rack from a flat sheet vorgestellk. 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 formed next to the flat area with increasing distance from the flat area with a rising course. 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.

The EP 1 123 855 A2 and the EP 1 132 277 A2 show mold elements in which weakenings are arranged on the inside of the wall in a region in which on the outside of the wall, the mold element is mounted in the form of a pressed-toothing.

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. To " Umformfechnik, Handbook for Industry and Science ", edited by Kurt Lange, Springer Verlag 1984 For example, major changes in shape can be defined for such changes in shape, which in the case of a planar shape change run in two directions (Vol. 1, page 144). When forming a sheet, for simplicity, it becomes a (piecewise) plane shape change state assumed and there are essentially two main deformation directions, one of which extends within the sheet metal piece. In the case of sheet bending, one of the main shape changes is tangent to the bendline. The juxtaposition of the main changes in shape of the individual subjected to the transformation volume elements within the sheet metal piece corresponds in the case of bending the bending line. Along these major changes in shape, the shape of the piece of sheet metal is plastically deformed. This juxtaposition of the main shape change in the Blecheben is to be referred to in the further analogous to the bending line as Hauptformänderungs line.

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 having the features of claim 9. In the dependent claims advantageous developments of the molding according to the invention or the manufacturing method according to the invention for the molded part are 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. For example, stresses, in particular bending stresses, are only transferred to a slight extent via weakenings, for example beads or millings, which extend transversely to a main strain-change line or a bending line. At least most of the stress is dissipated by deformation at the point of weakening. At edges of the material flow is hindered by the contact with the tool. Accordingly, an introduced on one side of the retaining edge voltage with the resulting Deformation be forwarded to a lesser extent on the other side of the retaining edge.

It is obvious that the bending line is selected, along which the deformation would be transmitted during the subsequent forming stages in the portion in which the molding element is arranged.

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 molding element may, for example, be a surface contour introduced into the wall of the molding within the subregion or a surface contour which is introduced into the wall of the molding Subregion introduced non-continuous or continuous recess or be formed by a plurality of such recesses.

In an advantageous embodiment of the invention, seen in the direction of a bending line of the molded part in front of and behind the partial area or the shaped element, ie seen in cross-section parallel to the bending line 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 molding element in the partial region of the molded part, at least one further deformation of the molded part, which represents or comprises in particular a bend of the molded part, carried out, wherein the respective introduced weakening and / or holding edge counteracts further uncontrolled deformation of the molded part in the partial area , Preferably, the partial area in which the mold element is located, in this case based on the bending line of the sheet metal piece formed during the bending operation, is delimited on both sides by at least one weakening and / or holding edge, this weakening or holding edge being transverse, preferably orthogonal, going to the bending line.

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 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 advantageously used in cases in which the molding element to be introduced into the partial area, because of restricted accessibility, can not be fully held until the finished formation of the component between the corresponding tool engraving of a top and bottom tool.

• Figur 1 eine erste Ausführungsform eines erfindungsgemäßen Formteils, welches in Form einer Zahnstange ausgebildet ist;
• Figur 2 das Ausgangswerkstück, die ebene Blechplatine, zur Herstellung der Zahnstange;
• Figur 3 eine erste Umformstufe zur Bildung der Zahnstange, im Querschnitt dargestellt;
• Figur 4 eine zweite Umformstufe zur Bildung der Zahnstange, im Querschnitt dargestellt;
• Figur 5 eine mögliche dritte Umformstufe zur Herstellung der Zahnstange, im Querschnitt dargestellt;
• Figur 6 eine Ausführungsform der fertig umgeformten Zahnstange im Werkzeug, entsprechend der Figur 1, im Querschnitt dargestellt;
• Figur 7 die halbfertige Zahnstange, entsprechend nach dem Umformschritt entsprechend der Figur 3 in isometrischer Ansicht;
• Figur 8 die halbfertige Zahnstange nach dem Einprägen der Verzahnung und der Schwächungen, korrespondierend mit der Figur 4 in Seitenansicht;
• Figur 9 eine Ausführungsform der erfindungsgemäßen Zahnstange, entsprechend der Figur 1 im Längsschnitt;
• Figur 10 einen Ausschnitt der erfindungsgemäßen Zahnstange, entsprechend der Ausführungsform der Figur 1 in Draufsicht auf die Verzahnungsseite der Zahnstange;
• Figur 11 die halbfertige Zahnstange, entsprechend nach dem Umformschritt entsprechend
• Figur 4 in isometrischer Ansicht;
• Figur 12 Ausschnitt Z aus Figur 6;
• Figur 13 ein zweites Ausführungsbeispiel eines erfindungsgemäßen Formteils, welche in Form einer eine Nockenkontur aufweisenden hohlen Stange ausgebildet ist, in isometrischer Ansicht;
• Figur 14 ein drittes Ausführungsbeispiel eines erfindungsgemäßen Formteils, welches in Form einer hohlen Stange mit einer Kulissenausnehmung ausgebildet ist, in isometrischer Ansicht;
• Figur 15 ein viertes Ausführungsbeispiel eines Formteils gemäß der Erfindung, im Querschnitt dargestellt, zusammen mit einem schematisch dargestellten Umformwerkzeug zur Durchführung eines Umformschritts dieses Formteils.

In the following, the invention will be explained by way of example with reference to schematic figures. The figures illustrate:

• FIG. 1 a first embodiment of a molded part according to the invention, which is in the form of a rack;
• FIG. 2 the starting workpiece, the flat sheet metal plate, for the production of the rack;
• FIG. 3 a first forming stage for forming the rack, shown in cross-section;
• FIG. 4 a second forming stage for forming the rack, shown in cross-section;
• FIG. 5 a possible third forming stage for the production of the rack, shown in cross section;
• FIG. 6 an embodiment of the finished formed rack in the tool, according to the FIG. 1 , shown in cross section;
• FIG. 7 the half-finished rack, according to the forming step according to the FIG. 3 in isometric view;
• FIG. 8 the half - finished rack after the impression of the toothing and the weakenings, corresponding to the FIG. 4 in side view;
• FIG. 9 an embodiment of the rack according to the invention, according to the figure 1 in longitudinal section;
• FIG. 10 a detail of the rack according to the invention, according to the embodiment of FIG. 1 in plan view of the toothed side of the rack;
• FIG. 11 the half-finished rack, according to the forming step accordingly
• FIG. 4 in isometric view;
• FIG. 12 Section Z out FIG. 6 ;
• FIG. 13 a second embodiment of a molded part according to the invention, which is in the form of a cam contour having a hollow rod, in isometric view;
• FIG. 14 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;
• FIG. 15 a fourth embodiment of a molding according to the invention, shown in cross-section, together with a schematically illustrated forming tool 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 are shown only schematically.

For better clarity, the tools in the FIGS. 5, 6 and 15 Dismantled and the sections are not partially shown as hatching.

In the FIG. 1 is a section of an embodiment of a shaped in the form of a rack 1 according to the invention molded part in 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. Relative to the tangential direction or circumferential direction 4, the portion 5 is delimited by weakenings 7, 8, 9, 10, 11, 12, which extend 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 in the sectional view ( FIG. 6 . 12 ) is clearly visible, the wall thickness of the wall 3 at the weakening points 7, 8, 9, 10, 11, 12 formed thinner relative to the output wall thickness or wall thickness in the environment. 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 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 of the wall 3.

In the FIGS. 9 and 10 is the embodiment of the rack 1 according to the invention in longitudinal section ( Fig. 9 ) and in a plan view of the toothing ( Fig. 10 ). In particular, based on the FIGS. 9 and 10 It can be seen that in the example, the portion 5 in the longitudinal direction 2 is additionally delimited by the holding edges 37, and bends 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 relative to the circumferential direction 4, are provided in order to reduce transmission of the stresses into the partial region 5. It is to be preferred if the length 25 of the weakenings 7-12, at least the length of the portion 5, that is at least the length of the toothing 6, measured in the longitudinal direction 2 corresponds. 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 impressions are provided as weakening both on the inner surface 14 and on the outer surface 15 of the wall 3, the depth of the groove can still be 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 retaining edges is also conceivable and possible on these longitudinal sides of the portion 5, wherein it remains to be seen that the embossed grooves shown in the example already act in addition to the effect of weakening as a retaining 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 of 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 in the preferred Case 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 still another weakening 11, 12 on the inner surface 14 of the wall. 3 are provided on both sides of the toothing, it is preferably in the circumferential direction 4 between the two externally arranged weakenings and / or holding edges 7, 8, 9, 10 are arranged.

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. In this case, an arrangement of retaining edges is preferable only on the outer surface 15 of the wall 3, since it is simply possible only during the first forming stages to achieve a tool contact between the retaining edge and tool engraving. 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. As a 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 geometric configuration of the weakenings is preferably to be designed so that a removal of the workpiece after the forming of the toothing is not hindered by undercuts.

Weakening and / or holding edges which delimit the partial region 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 39.

The process sequence for producing the rack from a flat plate 16 is in the FIGS. 2, 3 . 4, 5 and 6 exemplified in their main steps.

In a first step ( Fig. 3 ) is the flat sheet 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 of the two legs 19, 20 is arranged, 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 preceding forming step or integrated in this first step, as in Fig. 3 is illustrated has occurred. In the FIG. 7 is the workpiece after the first forming step illustrated in 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.

The FIG. 4 illustrates a second and third forming step for introducing the weakenings 7-12 and the toothing 6. In the preferred sequence of the second and third forming step carried out in a forming step summarized simultaneously 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 the 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 allows the indentations of the weakenings 11, 12 on the inner surface 14 of the wall 3. In particular, the stamp 26 can after deformation without damaging the inner surface 14 and the leg ends 21, 22 are moved out of the workpiece. In the die 27, at least the corresponding negative contours for the weakenings and the toothing 6 are formed. In the die 26, the negative contours for the weakenings and for the inner surface in the region of the toothing 6 are 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 in the FIG. 9 is shown.

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 the FIG. 11 is the formed workpiece, corresponding to the same intermediate stage of the forming sequence as in FIG. 4 illustrated, illustrated in isometric view. The weakenings 7, 9, limit the portion 5 in which the teeth 6 is introduced.

In the FIG. 8 is the workpiece after the completed second and third forming step 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 forming a facilitated bending along the fold lines 34, which are formed by the weakenings 7, 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 region 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.

The 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 is during the introduction of the toothing 6 to the bending together the ends 21, 22 of the side legs 19, 20 subsequent forming steps in the tool engraving. 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, in the FIGS. 5 and 6 illustrated, said forming steps 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.

• o in einem ersten Fertigungsschritt das ebene Blech in einem ersten Umformwerkzeug 17, 18 in eine Halbschalen-Form oder U-Form, umfassend zwei Schenkel 19, 20 mit zwei Enden 21, 22, die den Enden 21, 22 gegenüberliegend durch einen Verbindungsabschnitt 23 miteinander verbunden sind, umgeformt wird,
• o in einem zweiten Umformschritt eine oder mehrere Schwächungen 7, 8, 9, 10, 11, 12 und/oder Haltekanten, in tangentialer Richtung 4 vom Teilbereich 5 der Wandung 3, der in einem Bereich des Verbindungsabschnittes 23 angeordnet ist, beabstandet, in Längsrichtung 2 mindestens entlang eines Teils der Länge 25 des Teilbereichs 5 verlaufend, eingeformt werden,
• o in einem dritten Umformschritt in den Teilbereich 5 die Verzahnung 6 eingepresst wird und danach
• o in einem oder mehreren nachfolgenden Umformschritten die Enden 21, 22 der beiden Schenkel 19, 20 unter Ausbildung eines sich in Richtung der Längsachse erstreckenden Hohlraums zusammengebogen werden.

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 are connected, reshaped,
• 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 from the portion 5 of the wall 3, which is arranged in a region of the connecting portion 23, spaced, in the longitudinal direction 2 at least along a portion of the length 25 of the portion 5 extending, 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.

• o in einem ersten Fertigungsschritt das ebene Blech in einem ersten Umformwerkzeug 17, 18 in eine Halbschalen-Form oder U-Form, umfassend zwei Schenkel 19, 20 mit zwei Enden 21, 22, die den Enden 21, 22 gegenüberliegend durch einen Verbindungsabschnitt 23 miteinander verbunden sind, umgeformt wird,
• o in einem zweiten Umformschritt in den Teilbereich 5 die Verzahnung 6 eingepresst wird und
• o in einem dritten Umformschritt eine oder mehrere Schwächungen 7, 8, 9, 10, 11, 12, und/oder Haltekanten in tangentialer Richtung 4 vom Teilbereich der Wandung 3, der in einem Bereich des Verbindungsabschnittes 23 angeordnet ist, beabstandet, in Längsrichtung 2 mindestens entlang eines Teils der Länge 25 des Teilbereichs 5 verlaufend, eingeformt wird und danach
• o in einem oder mehreren nachfolgenden Umformschritten die Enden 21, 22 der beiden Schenkel 19, 20 unter Ausbildung eines sich in Längsachse erstreckenden Hohlraums zusammengebogen werden.

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, reshaped,
• 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 4 from the portion of the wall 3, which is arranged in a region of the connecting portion 23, spaced, in the longitudinal direction of the second running along at least part of the length 25 of the portion 5, is formed and thereafter
• 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 einem ersten Schritt eine oder mehrere Schwächungen 7, 8, 9, 10, 11, 12 und/oder Haltekanten, die einen Teilbereich 5 des ebenen Blechs 16 begrenzen eingebracht werden,
• o in einem weiteren Fertigungsschritt das ebene Blech in einem ersten Umformwerkzeug 17, 18 in eine Halbschalen-Form oder U-Form, umfassend zwei Schenkel 19, 20 mit zwei Enden 21, 22, die den Enden 21, 22 gegenüberliegend durch einen Verbindungsabschnitt 23 miteinander verbunden sind, umgeformt wird,
• o in einem weiteren Umformschritt, der vor der Ausbildung der U-Form, nach der Ausbildung der U-Form oder gemeinsam mit der Ausbildung der U-Form erfolgt, in den Teilbereich 5 die Verzahnung 6 eingepresst wird und danach
• o in einem oder mehreren nachfolgenden Umformschritten die Enden 21, 22 der beiden Schenkel 19, 20 unter Ausbildung eines sich in Richtung der Längsachse erstreckenden Hohlraums zusammengebogen werden.

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

• o in a first step, one or more weakenings 7, 8, 9, 10, 11, 12 and / or holding edges which delimit a partial region 5 of the planar 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, the ends 21, 22 opposite each other by a connecting portion 23 with each other are connected, reshaped,
• o in a further forming step, which takes place before the formation of the U-shape, after the formation of the U-shape or together with the formation of the U-shape, in the portion 5, the toothing 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.

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, such as in Fig. 1 is shown, 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 Weakenings 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 in FIG. 13 shown. 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 bending line of the rod 46.

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, in FIG. 13 not shown part are displaced at a take place in the longitudinal direction 39 of the rod displacement of the rod 46 (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 in turn in the longitudinal direction 39 extending weakenings, of which in FIG. 13 only the attenuations 7, 9 arranged on one side of the cam contour 40 are visible. Further, in relation to the longitudinal direction 39, weakenings may be arranged in front of and behind the cam contour 40 which extend transversely to the longitudinal direction 39 and of which in FIG FIG. 13 only the weakening 37 is visible.

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.

This in FIG. 13 schematically illustrated second embodiment differs from the first embodiment thus only by the nature of the arranged in the partial region 5 element element.

A third embodiment of the invention is in FIG. 14 shown schematically, which in turn 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 interact with a in FIG. 14 not shown, 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 in FIG. 15 shown schematically in cross section. 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 3 partially surrounding the cavity 49. Corresponding in cross section FIG. 15 seen through the molding 48 are on both sides next to the surface contour 42 weakenings 7, 8 of the wall 3 is arranged. These extend at right angles to the main deformation line 52 in the form of the bending line of the molded part 48. The linearly extending weakenings 7, 8 could in turn also include angles other than 90 ° relative to the bending line 52, wherein the angle enclosed by the bending line 52 preferably lies in the region between 45 and 135 °.

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

In FIG. 15 is shown together with the molding 48 schematically a tool with which the last forming step has been carried out and which includes the tool halves 43, 45. The engraving of the tool half 43 contains the negative shape of the surface contour 42. Furthermore, the tool half 43 has projections 53, 54, which in groove-shaped trained weakenings 7, 8 intervene. 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 FIG. 15 an application of the inventive solution is illustrated, in which a first region 57 of the mold element 42 is held to the finished formation of the molding 48 between the engraving of an upper mold 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 34 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.

Legend to the reference numbers:

1

rack

2

longitudinal axis

3

wall

4

circumferentially

5

subregion

6

gearing

7

weakening

8th

weakening

9

weakening

10

weakening

11

weakening

12

weakening

13

tooth

14

palm

15

outer surface

16

flat sheet metal

17

Forming tool, stamp

18

Forming tool, die

19

leg

20

leg

21

leg end

22

leg end

23

connecting portion

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

dental outlet

33

embossing depth

34

fold line

35

Weld

36

fold line

37

retaining edge

38

bow

39

longitudinal direction

40

cam contour

41

Kulissenausnehmung

42

surface contour

43

tool half

44

support plunger

45

tool half

46

pole

47

pole

48

molding

49

cavity

50

leg

51

leg

52

Main shape change line, bend line

53

head Start

54

head Start

55

bending nose

56

bending nose

57

first area

58

border area

α

angle

Claims (13)

1. Shaped part, which is produced from a plane metal plate (16) and which is of hollow form at least in sections and comprises in its hollow region a wall (3) which at least partly surrounds the hollow space (49) of the shaped part and has in at least a partial region (5) a shaped element (6, 40, 41, 42), characterised in that at least one local weakening (7 - 12) and/or holding edge is formed on the outer surface (15) of the wall (3), at a distance from the shaped element (6, 40, 41, 42) in the direction of a bending line (52) of the shaped part, and extends at an angle to the bending line (52) at least over part of the extent of the shaped element (6, 40, 41, 42) and beside the latter, at least one further shaping of the metal plate (16), which constitutes or comprises a bending of the shaped part, having been carried out after the formation of the shaped element (6, 40, 41, 42) in a partial region (5) of the metal plate (16), the respective formed weakening (7-12) and/or holding edge counteracting a further uncontrolled deformation of the shaped part in the partial region (5).
2. Shaped part according to Claim 1, characterised in that at least one weakening (7, 8) or holding edge is provided on both sides of the shaped element (6, 40, 41, 42) when seen in a cross-section parallel to the bending line (52) and/or in that at least one weakening (7, 8, 9, 10, 11, 12) and/or holding edge is oriented at right angles to the bending line (52).
3. Shaped part according to one of the preceding claims, characterised in that at least one weakening (7, 8, 9, 10, 11, 12) or holding edge is produced by impression on at least one surface (14, 15) of the wall (3) and/or in that at least one weakening (7, 8, 9, 10, 11, 12) or holding edge is produced by a rolled bead in the wall (3).
4. Shaped part according to one of the preceding claims, characterised in that at least one weakening (7, 8, 9, 10, 11, 12) is arranged on the inner surface (14) of the wall (3).
5. Shaped part according to Claim 4, characterised in that respectively two weakenings (7, 8, 9, 10) are arranged on the outer surface (15) of the wall (3) on both sides of the shaped element (6, 40, 41, 42).
6. Shaped part according to one of the preceding claims, characterised in that the shaped element (6, 40, 41, 42) is a surface contour of the wall or a recess in the wall (3).
7. Shaped part according to one of the preceding claims, characterised in that the shaped part extends in a longitudinal direction (39) and the bending line (52) runs at right angles to the longitudinal direction (39).
8. Shaped part according to one of the preceding claims, characterised in that the at least one weakening (7 - 12) and/or holding edge has a linear course.
9. Method for producing a hollow section of a shaped part or a hollow shaped part from a plane metal plate (16), the metal plate being shaped in such a way that a wall (3) which at least partly surrounds the hollow space (49) of the shaped part forms and has in at least a partial region (5) a shaped element (6, 40, 41, 42), characterised in that one or more weakenings (7 - 12) and/or holding edges are formed in the metal plate (16) on the outer surface (15) of the wall (3), at a distance from the shaped element (6, 40, 41, 42), which has already been formed or is still to be formed, in the direction of a bending line (52), and extend at an angle to the bending line (52) at least over part of the extent of the shaped element (6, 40, 41, 42), which has already been formed or is still to be formed, and beside the latter, and at least one further shaping of the metal plate (16), which constitutes or comprises a bending of the shaped part, is carried out after the formation of the at least one shaped element in a partial region (5) of the metal plate (16), the respective formed weakening (7-12) and/or holding edge counteracting a further uncontrolled deformation of the shaped part in the partial region (5).
10. Method according to Claim 9, characterised in that one or more weakenings (7 - 12) and/or holding edges are formed before at least one subsequent shaping step in which the plane metal plate (16) is brought into a bent shape or the metal plate which has already been brought into a bent shape is brought into a different bent shape and/or in that one or more weakenings (7 - 12) and/or holding edges are formed in the plane metal plate.
11. Method according to one of Claims 9 or 10, characterised in that the shaped element (6, 40, 41, 42) is supported in the die of a shaping tool (27, 29, 31, 43, 45), at least on the outer surface (15), during the shaping steps following the formation of the shaped element (6, 40, 41, 42).
12. Method according to one of Claims 9 to 11, characterised in that the plane metal plate (16) is shaped in a first shaping tool (17, 18) into a half-shell shape or U-shape, comprising two legs (19, 20) which are connected to one another by a connecting section (23) and each have an end (21, 22) remote from the connecting section.
13. Method according to Claim 12, characterised in that after that at least one further shaping step is carried out, in which the ends (21, 22) of the two legs (19, 20) are brought closer to one another or brought together and in which the at least one weakening (7 - 12) and/or holding edge has already been formed.

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