EP2598267B1 - Forging die and method - Google Patents

Description

The invention relates to a die for forging a toothed portion of a rack of a steering device with first and second die parts, of which the first die part has a first mold recess for forming the toothing of the rack and the second die part has a second mold cavity, the shape of the toothing opposite the back region of the rack has, and which can be moved together with forming an inserted into the die blank, starting from an open position in a closing direction to an end position in which they have a distance from each other, wherein in the region of the Formausnehmungen the die parts between the die parts a Hauptkavität is formed, which is open in the collapsed end position of the die parts on opposite sides to Nebenkavitäten out, which are each in a lying between the first and the second die portion. Further, the invention relates to a forging method for forging a toothed portion of a rack for a steering device, wherein a blank is formed between two die parts, of which the first die part, a first mold cavity for forming the teeth of the rack and the second die part, a second Formausnehmung has, which has the shape of the toothing opposite the back portion of the rack, and which are moved together with reshaping inserted into the blank blank, starting from an open position in a closing direction to an end position in which they have a distance from each other, wherein Is formed in the collapsed end position of the die parts on opposite sides to side cavities, each in a between the first and the second die lying lying area, and wherein during the collapse of the die parts material of the blank is displaced into the secondary cavities.

Racks for steering devices of motor vehicles, which have constant toothing, are often produced by machining, with high precision being achievable. Such racks can also be made with sufficient accuracy by forming. Forming processes are often more economical than machining processes. Steering racks with variable teeth, in which the distance of the teeth and / or the shape of the teeth and / or the inclination of the teeth changes over the extent of the toothing, are very difficult to produce. For economical production in large series, the manufacturing process becomes more complex.

Steering racks are known which have a triangular cross section or a Y cross section in the region of their toothed ends. For example, such a rack goes out of the EP 0 738 191 B1 and the production of this rack is made by hot forging. Such racks are well suited for variable gears and are supported in their guide against the influence of rolling moments, which occur by contact forces between the teeth of the pinion and the teeth of the rack due to inclinations, by their longitudinal guide. Furthermore, there are steering racks with a round back profile or D-section. Such have advantages over Y-section racks in manufacturing, even in their non-toothed areas, and in mounting and sealing the rack. The required installation space is significantly smaller and the geometry of the rack supporting the pressure piece is easier. However, these racks are more susceptible to the influence of rolling moments, which can lead to tilts with noise developments (rack roll). For forming technical production of racks, especially round sprockets, for steering devices forging with burr and forging are known without burr.

In a forging method with burr, in which a die of the type mentioned is used, when the two die parts material of the blank from the main cavity in both sides of the main cavity in the region of the parting plane between the die parts lying secondary cavities pushed out and this material forms burrs, the removed after the forging process. These burrs also accommodate volume tolerances of the blank. As the die parts collapse, the opening from the main cavity to the sub-cavities (also referred to as a "burr gap") progressively decreases, increasing the die internal pressure and allowing portions of the material to flow from the main cavity into the sub-cavities. In particular, at the edges, there is a strong flow of material of the material of the blank under high pressure. This leads to heavy wear on the die parts, in particular at the edges of the die parts, which limit the Hauptkavität to the Nebenkavitäten. The service life of the die parts are therefore low. Furthermore, the achievable gearing accuracies are limited. These also depend on the burr geometry, which can only be changed by reworking the die parts themselves.

From the EP 1 007 243 B1 For example, a burr forging method is known for making round spine racks with burrs, the subcavities limiting the flow of the blank material from the main cavity. The total volume of the secondary cavities in the end position of the die parts corresponds to the volume difference between the rack blank and the finished rack in the toothed area. The secondary cavities are thus closed in the end position of the die parts and completely filled with blank material. It can be formed by an increased hydrostatic pressure. A disadvantage of this method is that the volume of the blank must be defined very precisely, so it must be exactly pre-ground or otherwise manufactured. This increases the production cost considerably.

From the WO 2005/053875 A1 is a forging process without a burr for the production of Rundrückenzahnstangen out. Between the two die parts two punches are provided. In the closed state of the two die parts are these on both sides of the two stamps. The main cavity is not yet completely filled with the material of the blank at this time. As a result, the two punches are pressed into the main cavity, reducing the volume of the main cavity, whereby the blank material is pressed on all sides of the walls of the main cavity. The non-generic die used in this method thus has no secondary cavities. Also in this method, the volume of the blank must be precisely defined. In the region of the rack in which the toothing is formed, therefore, a preform is formed, which is reduced by the volume fraction that would be incurred in a machining production. In addition, it has been found that in order to obtain an appealing result, in general a preform approximated geometrical shape of the preform is required. The preform geometry must be determined empirically, which is technologically complex. In addition, preforming causes significant additional costs, due to the machining itself and the volume accuracy requirements. Furthermore, the process management is complex and even small deviations in the volume of the preform or in the volume of the main cavity can lead to burr formation, whereby further additional costs are generated as a result of the required rework.

The object of the invention is to provide a die or a forging method of the type mentioned, by which an improved production of a rack for a steering device is made possible. According to the invention, this is achieved by a die with the features of claim 1 or by a forging method with the features of claim 11. In the dependent claims, advantageous developments are included.

The die according to the invention has an open main cavity, wherein connect in the collapsed end position of the two die parts to the main cavity, which is formed in the region of the mold recesses between the die parts, on both sides Nebenkavitäten. In this occurs during the merge of the die parts material of the blank, whereby lateral protuberances or burrs are formed. According to the invention, the die has in addition to the two die parts at least two secondary moldings. These are located respectively in the region which lies between the first and the second die part, and the walls which delimit the secondary cavities are at least partially formed by the secondary moldings. The secondary moldings are each displaceable in an adjustment direction relative to the die parts, which is angled to the closing direction. The angle occupied by the direction of adjustment of the respective secondary molded part with the closing direction, is favorably in an interval of 45 ° to 135 °, wherein angle in the range of at least 70 ° to 110 ° is preferred and a right angle to the closing direction is particularly preferred.

The forging method according to the invention for forging a toothed portion of a rack is characterized by the features of claim 11. The displaced in the side cavities material flows to side moldings, which in each case partially limit the flow of the displaced material in the respective Nebenkavität. The displaced into the respective Nebenkavität material is displaced into a space which is disposed within the respective Nebenkavität (ie forms part of the respective Nebenkavität) and is limited by a directed towards one of the die parts surface of the respective secondary molding and the end face of the die or by a surface of the respective secondary molding directed in the direction of one of the die parts and a surface of a further secondary molding part which is arranged in the same secondary cavity. The respective intermediate space thus lies between the respective secondary molded part and one of the die parts or between two respective secondary molded parts which in each case partially delimit the same secondary cavity.

The forging method according to the invention allows a combination of a free (= only partially limited to walls of the die or in other words a partially unlimited) deformation and a tool-bound deformation of the material of the blank into the secondary cavities inside. The flow of material into the secondary cavities is necessary in order to achieve the formation of the desired shape of the rack, thereby reducing the preliminary work for preforming blanks.

This design makes it possible to position the secondary molded parts in a defined manner, or readjust or replace them as wear increases. An exchange or a post-processing of a die part can be avoided or at least delayed.

Furthermore, the geometry of the secondary cavities is at least co-determined by the secondary moldings. As a result of the geometry and / or adjustment of the secondary moldings, the geometry of the secondary cavities can thus be changed or adapted, as a result of which the material flow (material flow) of the blank during forging can be optimized. Quality improvements of the finished rack can be achieved. In particular, the flow resistance for the displaced material of the blank can be adjusted, wherein a Zahnausformung at, at least over part of the Zustellweges the die parts, lower pressures can be achieved, which in turn has a time-favorable effect. In addition, the risk of cracking in the rack can be reduced.

Advantageously, the secondary cavities are not completely filled with the material of the blank in the collapsed end position of the die parts, ie in any case there are areas into which no material of the blank passes. Preferably, the secondary cavities are open to the outside. That is, the Nebenkavitäten are not only open to the main cavities, but are also at least one other site not limited by a wall. However, an "open" design of the secondary cavities in the above-mentioned sense would also be present if the secondary cavities in the end position of the die parts are closed to the outside, but their volume is so great that it is not completely filled by the displaced material of the blank. In a preferably used cylindrical blank, the volume of the secondary cavities together is thus greater than the volume fraction of the blank, which would be removed in a machining production of the rack.

Conveniently, there is a gap between a respective secondary molding and an end face of one of the die parts, which points to the other of the die parts, or between two secondary moldings, each of which limits the same Nebenkavität sections. Its width is reduced when moving together the die parts. In the collapsed end position, however, this gap remains, ie. is not completely closed, wherein its width in the collapsed end position (measured in the closing direction) is preferably at least 2mm.

By means of the secondary moldings, the material flow can be controlled in such a way that, although the secondary cavities are not completely filled with material, the yield stresses required for the formation of the toothing are achieved. Nevertheless, the workpiece blank must be designed less precisely than in the prior art, since the free space in the Nebenkavität material volume fluctuations can be largely compensated.

An advantageous embodiment of the invention provides that a respective secondary molded part has first and second side surfaces, of which the first side surface abuts against an end face of one of the two die parts facing the other die part, and at least a portion of the second end face defines a respective side cavity Wall forms. The first and second side surfaces of the secondary molding are connected to one another via an end face. Conveniently, this end face closes with the closing direction at an angle of less than 45 °, preferably less than 20 °, a parallel alignment with the closing direction being particularly preferred. The end face of a respective secondary molding is preferably withdrawn relative to the main cavity, so does not protrude into the main cavity or flush with it but rather forms a wall bounding the secondary cavity to which blank material emerging from the main cavity moves when the die parts move together.

Advantageously, the end face opposite the main cavity at least one-tenth, preferably at least one-fifth of the distance of the Gesenkenteile in her End position withdrawn. In this case, between the end face and the main cavity extends a portion of the (adjacent to the mold cavity) end face of the die on which abuts the auxiliary molding, the extension of this portion of the end face of the die seen in cross section through the die (the perpendicular to the longitudinal extent of the rack or the main cavity is aligned) at least one tenth, preferably at least one fifth of the distance of the end faces of the die parts (measured in areas adjacent to the mold cavities) in their contracted end position amounts.

The thickness of the secondary moldings (measured in the closing direction) is favorably at least a quarter, preferably at most three quarters, of the distance of the mutually facing end faces of the die parts (in their lying next to the mold cavities sections) when the die parts occupy their contracted end position.

An advantageous embodiment of the method according to the invention provides that the secondary moldings are kept stationary during the forging of the toothed portion of the rack relative to their adjustment directions, ie no movement in the adjustment takes place, at least from the time from which material of the blank starts to the secondary moldings , The secondary moldings are in this case stationary relative to one of the two die parts, preferably auxiliary mold parts are held only on the fixed die part, which thus are stationary relative to the latter during forging.

In another possible embodiment of the method according to the invention, however, at least one of the secondary moldings could be adjusted during its forging of the toothed portion of the rack in its direction of adjustment. This can further influence the material flow. Such an adjustment of at least one of the secondary moldings, favorably all secondary moldings, this can be done simultaneously with the collapse of the die parts and / or thereafter. In this case, a path-controlled method of movement of the secondary molded parts is conceivable and possible, in which by corresponding wedge and or slide guides the movement is coupled to the closing movement of the die parts. Alternatively, one or both of the secondary moldings can be selectively moved with extra hydraulic punches during the forming process.

• Fig. 1 eine schematische Darstellung einer Lenkvorrichtung für ein Kraftfahrzeug;
• Fig. 2 eine Schrägsicht eines Abschnitts der Zahnstange der Lenkvorrichtung (der verzahnte Bereich verkürzt und vereinfacht dargestellt);
• Fig. 3 eine schematische Darstellung eines Ausführungsbeispiels eines erfindungsgemäßen Gesenks in der Offenstellung, mit eingelegtem Rohling, im Querschnitt (rechtwinkelig zur Längsersteckung des Gesenks bzw. rechtwinkelig zur Längsachse der Zahnstange);
• Fig. 4 eine Darstellung analog Fig. 3 während des Zusammenfahrens der beiden Gesenkteile;
• Fig. 5 eine Darstellung analog Fig. 3 in der zusammengefahrenen Endstellung der Gesenkteile;
• Fig. 6 eine Darstellung analog Fig. 3 nach dem Schmieden, die geschmiedete Zahnstange aus dem Gesenk entnommen;
• Fig. 7 und 8 eine Seitenansicht und eine Draufsicht auf die Zahnstange nach dem Schmieden;
• Fig. 9 einen Querschnitt durch das Gesenk in der zusammengefahrenen Endstellung der beiden Gesenkteile, ohne die geformte Zahnstange, zur Veranschaulichung;
• Fig. 10 bis 13 Darstellungen analog Fig. 3 bis 6 einer zweiten Ausführungsform der Erfindung;
• Fig. 14 eine Darstellung analog Fig. 5 einer dritten Ausführungsform der Erfindung;
• Fig. 15 bis 17 Darstellungen analog Fig. 3 bis Fig. 5 einer vierten Ausführungsform der Erfindung;
• Fig. 18 eine Darstellung analog Fig. 5 einer fünften Ausführungsform der Erfindung;
• Fig. 19 eine Darstellung analog Fig. 5 einer sechsten Ausführungsform der Erfindung.

Further advantages and details of the invention are explained below with reference to the accompanying drawings. In this show:

• Fig. 1 a schematic representation of a steering device for a motor vehicle;
• Fig. 2 an oblique view of a portion of the rack of the steering device (the toothed area shown shortened and simplified);
• Fig. 3 a schematic representation of an embodiment of a Gesenk according to the invention in the open position, with inserted blank, in cross section (perpendicular to the longitudinal extent of the die or at right angles to the longitudinal axis of the rack);
• Fig. 4 a representation analog Fig. 3 during the collapse of the two die parts;
• Fig. 5 a representation analog Fig. 3 in the collapsed end position of the die parts;
• Fig. 6 a representation analog Fig. 3 after forging, the forged rack removed from the die;
• FIGS. 7 and 8 a side view and a top view of the rack after forging;
• Fig. 9 a cross section through the die in the collapsed end position of the two die parts, without the molded rack, for illustrative purposes;
• Fig. 10 to 13 Representations analog Fig. 3 to 6 a second embodiment of the invention;
• Fig. 14 a representation analog Fig. 5 a third embodiment of the invention;
• 15 to 17 Representations analog FIG. 3 to FIG. 5 a fourth embodiment of the invention;
• Fig. 18 a representation analog Fig. 5 a fifth embodiment of the invention;
• Fig. 19 a representation analog Fig. 5 a sixth embodiment of the invention.

Similar or equivalent elements are denoted by the same reference numerals in the figures.

Fig. 1 schematically shows a possible embodiment of a steering device for a motor vehicle. The steering device comprises a steering wheel 1 and a steering shaft 2, which comprises two or more articulated sections. To the steering shaft 2, a steering pinion 3 is rotatably mounted or coupled, which meshes with a toothed portion 5 of a rack 4. The rack 4 is slidably mounted in the direction of its longitudinal axis, for example, in a steering housing 6. With the two ends of the rack 4 are tie rods via ball joints, not shown, directly or indirectly in connection. The tie rods 7 are connected in a known manner via stub axles, each with a steered wheel of the motor vehicle.

To assist the driver in the steering movement different devices may be present, for example, on the rack 4 acting auxiliary drives or acting on the steering shaft 2 auxiliary drives.

An enlarged portion of the rack 4 is in Fig. 2 shown in oblique view. The rack 4 has a portion with a toothing 5, which in Fig. 2 shortened for simplicity. The toothed portion extends over a portion of the longitudinal axis 39 of the rack 4 lying parallel to the longitudinal extension of the rack 4. In the installed state, the rack 4 is slidably mounted in a direction parallel to its longitudinal axis 39 displacement direction 40, which Fig. 2 indicated by a double arrow.

The teeth 8 of the toothed portion are in Fig. 2 shown as straight teeth 5 with equal distances and the same tooth shapes. Often deviating tooth geometries should be used, provided with helical gears could be. The distances of the teeth and / or their inclinations and / or their shapes can vary over the extent of the toothed section, one then speaks of variably toothed racks.

In the embodiment shown, the toothing 5 diametrically opposite region of the rack 4 is cylindrical. A rack for a steering device having such a shape is also referred to as Rundrückenzahnstange. In the toothing 5 diametrically opposite area (= back area) is the contour of the rack 4 seen in cross-section thus arcuate. In the area of the toothing 5, the rack is formed flattened when viewed in cross-section. In view of this training, such a rack is also referred to as a rack with a D-profile.

A die (= tool) for forging the toothed portion of the rack is in Fig. 3 schematically shown in cross-section in its open position. The die comprises first and second die parts 9, 10. The first die part 9 has a first die recess 11, which serves for forming the section having the toothing 5. The second die part 10 has a second mold recess 12. This has the shape of the toothing 5 diametrically opposite back portion of the rack in the toothed portion, is thus formed in the exemplary embodiment in cross-section at right angles to the longitudinal axis 39 circular arc.

In the exemplary embodiment shown, the first die part 9, which has the first die recess 11 forming the toothing, is movable and the second die part 10 is stationary. In this case, the first die part 9 is moved starting from the open position in the closing direction 13 in the direction of the second die part 10 until a fully compressed end position has been reached. The merged end position is in Fig. 5 (With the rack 4 shaped blank 15) and for further illustration in Fig. 9 (Without a rack shaped blank 15) shown. An inverted configuration in which the first die part 9 is fixed and the second die part 10 in a closing direction (which is opposite to the closing direction 13) in the direction of the first die part 9 for forming the toothed portion of the rack is adjustable, is conceivable and possible.

Between the die parts 9, 10, in the area in which the mold recesses 11, 12 lie, a main cavity 14 is formed, cf. Fig. 9 , The main cavity 14 thus comprises the regions of the mold recesses 11, 12 and the region between the two die parts 9, 10 lying between the mold recesses 11, 12 Fig. 9 this lying between the mold recesses 11, 12 region is schematically delimited by dashed lines opposite the side of the mold recesses 11, 12 lying areas that lie between the die parts 9, 10. The boundaries are here in Fig. 9 drawn in a straight line between edges on the edges of the mold recesses 11, 12 extending. Instead, the delimitations could also continue the course of the second mold recess 12, in this case in the form of an arc of a circle, that is, in accordance with the cross-sectional contour of the cylindrical blank 15 inserted into the second mold recess 12 before it is formed. As Hauptkavität 14 can also in cross-section seen (corresponding Fig. 9 ) of the mold space, which is limited by the mold cavities 11, 12 of the two die parts 9, 10, in the position in which the two die parts 9, 10 are moved together in the forming process most closely, and by the lines which are formed by the tangential extensions of the inner contours of the mold recesses 11, 12 of the respective die part 11, 12 beyond the associated edge 27, 28 and 24, 25 to the intersection of these tangential extensions, starting from the two die parts 9, 10. The exact course of demarcation So if, for example, the in Fig. 9 shown or the further described option is chosen, is irrelevant.

The main cavity 14 is thus on opposite sides - with respect to a parallel to the closing direction 13 and through the die parts 9, 10 and through the (deformed) blank 15 extending center plane - open. To the main cavity 14 in this case close on both sides Nebenkavitäten 16, 17 at. The openings between The main cavities 14 and the secondary cavities 16, 17 may also be referred to as "burr gaps". The secondary cavities 16, 17 are each within a range that lies between the two die parts 9, 10, and that these areas are on both sides (relative to the aforementioned center plane) next to the mold cavities 11, 12th

In the areas lying between the die parts 9, 10 and on both sides of the mold recesses 11, 12 further each a separate auxiliary molding 18, 19 is arranged. A respective secondary molding 18, 19 has first and second side surfaces 20, 21 and an end face 22 directed to the main cavity 14 and connecting the first and second side surfaces 20, 21. The first side surface 20 of the respective secondary molded part 18, 19 bears against the end face 23 of the second die part 10 which is directed towards the first die part 9. The opposite second side surface 21 of the respective secondary molding 18, 19 forms a respective side cavity 16, 17 bounding wall. The end face 22 of the respective secondary molding 18, 19 is retreated relative to the respective edge 24, 25, which lies between the end face 23 of the second die part 10 facing the first die part 9 and the second die recess 12 of the second die part 10. The distance a of the respective secondary molding 18, 19 from the respective edge 24, 25 is favorably at least one tenth, preferably at least one fifth of the distance s, the two die parts 9, 10 and their end faces 26, 23 from each other. The portion of the end face 23 of the second die part lying between the respective secondary mold part 18, 19 and the respective edge 24, 25 of the second die part 10 forms a further section of the walls delimiting the respective secondary cavity 16, 17.

A further section of the walls delimiting the respective secondary cavity 16, 17 is further formed by the end face 26 of the first die part 9 facing the second die part, these sections of the walls respectively adjoining the edges 27, 28 which are located between the end face 26 of the first die part 9 and the first mold recess 11 of the first die part 9 lie.

A respective auxiliary molding 18, 19 is slidably mounted relative to the fixed second die part 10 in the respective adjustment direction 29, 30. The positioning directions 29, 30 are in the embodiment shown parallel to each other and perpendicular to the closing direction 13 and the longitudinal axis 39. Also, angular orientations of the adjusting directions 29, 30 with respect to the closing direction 13 and / or with respect to the longitudinal axis 39 are conceivable and possible, the positioning directions 29, 30 do not have to be parallel to each other. Deviations from the perpendicular orientation to the closing direction 13 and / or the longitudinal axis 39 of less than 20 ° are preferred.

The end faces 22 of the secondary moldings 18, 19 are flat in the embodiment shown and are parallel to the closing direction 13 and parallel to the longitudinal axis 39. The end faces 22 of the opposing secondary moldings 18, 19 point in the direction of the main cavity 14 and in this case preferably to a central region of the rack to be formed 4th

The end surfaces 22 could also include an angle with the closing direction 13 and / or with the longitudinal axis 39, which is desirably less than 45 °, preferably less than 20 °.

The forging of the rack is described below with reference to Fig. 3 to 6 explained.

In the open position of the two die parts 9, 10, the blank 15 is inserted into the second mold recess 12 of the fixed second die part 10, cf. Fig. 3 , The blank 15 in this case has a suitable temperature for hot forging. This is for a blank made of steel above the recrystallization temperature of steel, preferably between 600 ° and 1250 ° Celsius.

In principle, however, the tool and the method can also be used for cold forging. Due to the high forming forces and the resulting tool loads, hot forming is preferred in the case of steel forming.

As a result, the movable first die part 9 is moved in the closing direction 13, wherein the blank 15 is formed after the impact of the first die part 9 and begins to flow under the forming hydrostatic pressure in the plasticized state. An intermediate position during the collision of the two die parts 9, 10 is in Fig. 4 shown. The deformation of the blank 15 has already been used and material of the blank has leaked into the region of the secondary cavities 16, 17, whereby material of the blank has already been applied to the end faces 22 of the secondary shaped parts 18, 19.

During further movement of the first die part 9 in the closing direction 13, the blank 15 is further deformed and further material of the blank 15 passes into the side cavities 16, 17. With continuous movement of the die parts 9, 10 material of the blank passes into the respective gap 42, 43 between the second side surfaces 21 of the side mold parts 18, 19 (these second side surfaces 21 are the first side surfaces 20, which abut one of the die parts 9, 10, here on the second die part 10) and the end face 26 of the first die part 9 (if the secondary moldings 18, 19 would abut with their one side surface on the first die part 9, the respective gap would be between the other side surface of the respective auxiliary molding 18, 19 and the end face 23 of the second die part 10). These intermediate spaces 42, 43 decrease as the first die part 9 approaches the collapsed end position of the die parts 9, 10 which are in Fig. 5 is shown. It comes thereby in the last section of the Zusammenfahren to an increased hydrostatic pressure in the material of the blank 15. Under this high pressure, there is also an increased flow of the material of the blank 15 around the edge 31 of the respective auxiliary molding 18, 19, which between the said gap limiting second side surface 21 and the end face 22 of the respective auxiliary molding 18, 19 is located. These edges 31 are thus exposed to a relatively increased wear.

After the die parts 9, 10 have reached the merged end position, cf. Fig. 5 , And the forging method of the blank 15 is completed, the first die part 9 is opened against the closing direction 13 and formed by forming the blank 15 rack 4 is removed from the die, see. Fig. 6 ,

In Fig. 6 the arcuate profile 41 in the non-toothed portion of the rack 4 is visible. The mold recesses 11, 12 of the die parts 9, 10 extend into the non-toothed portion of the rack 4, which is indicated for the die part 9 by a dashed line.

The rack 4, after forging still on both sides ridges 32, 33, which can be separated in the sequence.

The secondary moldings 18, 19 thus represent at least parts of the geometry of the ridges 32, 33. Thus, they also influence the flow of the material of the blank 15 during the forging process.

In the forging method of the embodiment described above, the secondary moldings 18, 19 remain stationary relative to the second die part 10. With increasing wear, the secondary moldings 18, 19 can be adjusted by a displacement in the respective adjustment direction 29, 30. Here, a stop plate 34, 35, which lies between the directed away from the main cavity 14 end of a respective auxiliary molding 18, 19 and a respective stop 36, 37, are replaced. The stops 36, 37 are stationary to the die part, on which the respective auxiliary molding 18, 19 is displaceably guided, here so the second die part 10th

As a result of this adjustment of the secondary moldings 18, 19, the changes in the material flow resulting from the wear can be at least partially compensated. The service life of the die can be increased thereby.

If the wear on the secondary moldings 18, 19 has become too large, they can be replaced in a simple manner, without the reworking of the die parts 9, 10 itself are required. The wear occurring at the die parts 9, 10 is much lower than the wear occurring at the secondary moldings 18, 19. Around the edges 24, 25, 27, 28 of the die parts 9, 10 occurs in the last portion of the collapse of the die parts 9, 10, in which the hydrostatic pressure is particularly high, a significantly lower flow.

It would also be conceivable and possible to make the secondary moldings 18, 19 adjustable during the process (between individual forging processes). It could be provided for this purpose corresponding actuators, of which the secondary moldings 18, 19 can be adjusted in the adjustment directions 29, 30.

When setting up the forging process, optimizations of the flow can be made in a simple manner. For this purpose, the positions of the secondary moldings 18, 19 can be changed and / or secondary moldings with different geometries, for example in terms of their thickness (= the distance between their side surfaces 20, 21) are used. Thus, optimizations of the flow can be carried out without the die parts 9, 10 themselves being processed.

A second embodiment of the invention is in the Fig. 10 to 13 shown. This embodiment corresponds to the embodiment described above, except for the differences described below.

The secondary moldings 18, 19 are also here on the fixed second die part 10 in the adjustment directions 29, 30 slidably mounted. In the contracted end position of the die parts 9, 10 are the one side surfaces 20 of the secondary moldings 18, 19 but not on the second die part 10 but on the end face 26 of the first die part 9, see. Fig. 12 , These side surfaces bearing against one of the die parts 9, 10 are again referred to as first side faces 20. The opposite second side surfaces 21 are directed to the end face 23 of the second die part 10 and spaced therefrom. Between these second side surfaces 21 and the end face 23 is thus a gap 42, 42, which is a part of the side cavities 16, 17 and in which in the last portion of the collapse of the die parts 9, 10 material of the blank 15 flows, as from the comparison of FIGS. 11 and 12 is apparent.

The secondary cavities 16, 17 are in this embodiment in the collapsed end position of the die parts 9, 10 not open to the outside. However, these secondary cavities 16, 17 are only partially filled with the displaced material of the blank 15 in the end position of the die parts 9, 10. In this sense, it is also possible to speak of "open" secondary cavities or to speak of an "open total cavity" which comprises the main cavity 14 and the secondary cavities 16, 17.

The ridge geometries 32, 33 differ from the geometry of the ridges 32, 33 of the first embodiment.

The secondary moldings 18, 19 remain stationary during the collapse of the die parts 9, 10.

Fig. 14 shows a third embodiment, which apart from a modification in the region of the secondary moldings 18, 19 corresponds to the first embodiment. The secondary moldings 18, 19 have here in the region of their ends directed towards the main cavity 14 projections 38, through which the intermediate space 42, 43 between the secondary moldings 18, 19 and the end face 26 of the first die part 9 in the region of the projections 38 is reduced. Thereby punctures in the ridges 32, 33 are formed, whereby the separation of the ridges 32, 33 is facilitated. In order to place the punctures at the starting point of the ridges 32, 33 of the trainees main body of the rack 4, the side moldings 18, 19 here continue to the main cavity 14, ie the end faces 22 of the secondary moldings 18, 19 limit the Hauptkavität. The material emerging into the secondary cavities passes directly here into the interspaces lying between the secondary mold parts 18, 19 and the end face 26 (located next to the mold cavity 11) of the second die part 9 42, 43. The secondary moldings 18, 19 remain stationary when the die parts 9, 10 move together.

Also, a storage of the secondary moldings 18, 19 analogous to the second embodiment would be possible to form such punctures. The projections 38 would then be aligned with the end face 23 of the second die part 10.

A fourth embodiment will be described with reference to FIG 15 to 17 explained. The storage of the secondary parts 18, 19 corresponds to that in the Fig. 3 to 9 illustrated first embodiment, but could for example also in the Fig. 10 to 13 correspond to the embodiment shown. In contrast to the embodiments described above, the secondary moldings 18, 19 in this embodiment, during the collision of the Gesenkenteils 9, 10 in the respective adjustment direction 29, 30 method, and in any case from the time from which displaced material of the blank 15 to them starts (previously they can be stationary or already be moved). This is also from the comparison of FIGS. 16 and 17 clear. It may be further influenced by the flow of the material of the blank 15. By influencing the material of the blank such an optimization of the flow processes and thus of the entire forging process can be achieved, for example, to increase the hydrostatic pressure in a final section of the collapse of the die parts 9, 10 again. In this case, however, material can continue to flow into the secondary cavities 16, 17, since they are in any case not filled completely. At least in the last section of the merging of the die parts 9, 10 before reaching the contracted end position material of the blank 15 passes into the intermediate spaces 42, 43 which lie between the side mold parts 18, 19 and the end face 26 of the die part 9.

In addition to the optimization possibilities of the flow in the establishment of the forging process by different geometries of the secondary moldings 18, 19 can here be optimizations by the positions and movements of the secondary moldings 18, 19 (which may also be referred to as punches, at least in this embodiment) during forging.

The adjustment of the secondary moldings 18, 19 can be done by actuators not shown in the figures. Furthermore, a coupling with the movement of the adjustable die part 9 can take place, for example, in that during the movement of the die part 9 inclined surfaces are adjusted, against which the ends of the side moldings 18, 19 remote from the main cavity rest.

Fig. 18 shows a fifth embodiment, which apart from the shape of the mold recess 12 of the second die part 10 corresponds to the first embodiment. The mold recess 12 has here wedge-shaped mutually extending side surfaces, whereby the toothing 5 opposite back region of the rack 4 is formed over the toothed portion with a corresponding shape. The trained rack shape could also be referred to as a rack with triangular cross-section.

Fig. 19 shows a sixth embodiment, which apart from the differences mentioned below corresponds to the first embodiment. Here, on both the first die part 9 and the second die part 10, secondary mold parts 18, 18 ', 19, 19' are displaceably mounted in the positioning directions 29, 30. In each case one of the side surfaces 20, 20 'of the secondary moldings 18, 18', 19, 19 'abuts the respective die part 9, 10. The respective mutually facing side surfaces 21, 21 'of lying on the same side of the main cavity side moldings 18, 18' and 19, 19 'have between them a gap, the thickness of which decreases when moving together the die parts 9, 10, in the moved together end position of the Gesenkteile 9, 10 but not completely closed. At least in the last section of the collapse of the die parts 9, 10, material of the blank 4 flows into these intermediate spaces 42, 43.

The secondary moldings 18, 19 are withdrawn relative to the main cavity, while the secondary moldings 18 ', 19' are flush with the main cavity and their, Here, inclined end faces represent portions of the walls delimiting the main cavities. Various modifications to this are possible, for example all ancillary mold parts could be withdrawn from the main cavity 14. In preferred embodiments, at least two of the secondary moldings 18, 18 '; 19, 19 'withdrawn from the main cavity.

The displaceable bearings of the secondary moldings 18, 18 ', 19, 19' on the die parts 9, 10 are in Fig. 19 for the sake of simplicity not shown. For adjustment when wear begins again turntable 34, 34 ', 35, 35' may be provided, for example.

In further exemplary embodiments, displaceably mounted secondary molded parts could be provided only on the movable die part 9.

If separate secondary moldings are provided on both the fixed die part 10 and the movable die part 9 of the die parts 9, 10, then at least the secondary moldings arranged on one of the die parts 9, 10 are displaceable relative to the die part 9, 10 in positioning directions 29, 30 stored, preferably then such a displaceable storage for all secondary moldings 18, 19 is provided.

In the figures, the fixed die part 10 is shown below and the blank 15 is inserted into this fixed die part. A reverse arrangement, wherein the blank 15 is inserted into the movable die part 9 is also possible.

In the exemplary embodiments shown, the mold recess forming the toothing is arranged in the movable die part 9. An arrangement in the fixed die part 10 is possible. Legend to the reference numbers: 1 steering wheel 22 face 2 steering shaft 23 face 3 steering pinion 24 edge 4 rack 25 edge 5 gearing 26 face 6 steering housing 27 edge 7 tie rod 28 edge 8th tooth 29 setting direction 9 first die part 30 setting direction 10 second die part 31 edge 11 first mold recess 32 ridge 12 second mold recess 33 ridge 13 closing direction 34 Coupling pad 14 main cavity 35 Coupling pad 15 blank 36 attack 16 secondary cavity 37 attack 17 secondary cavity 38 head Start 18, 18 ' Besides molding 39 longitudinal axis 19, 19 ' Besides molding 40 displacement direction 20, 20 ' first side surface 41 course 21 21 'second side surface 42 gap 43 gap

Claims (14)

1. Die for forging a portion having a toothing (5) of a toothed rack (4) of a steering device, comprising first and second die parts (9, 10), of which the first die part (9) has a first moulding recess (11) for moulding the toothing (5) of the toothed rack (4), and the second die part (10) has a second moulding recess (12), which has the form of the back region of the toothed rack (4), lying opposite the toothing (5), and which can be moved together in a closing direction (13) from an open position into an end position, in which they are at a distance (s) from one another, while shaping a blank (15) placed into the die, wherein, in the region of the moulding recesses (11, 12) of the die parts (9, 10), there is formed between the die parts (9, 10) a main cavity (14), which in the moved-together end position of the die parts (9, 10) is open on opposite sides towards secondary cavities (16, 17), which respectively lie in a region lying between the first and second die parts (9, 10),
   characterised in that the die further has at least two secondary moulding parts (18, 19), which respectively lie in the region lying between the first and second die parts (9, 10) and by which the walls bounding the secondary cavities are at least partially formed, and which are respectively displaceable with respect to the die parts (9, 10) in an adjusting direction (29, 30) oriented at an angle to the closing direction (13).
2. Die according to claim 1, characterised in that the adjusting direction (29, 30) of the respective secondary moulding part (18, 19) forms an angle of at least 45°, preferably at least 70°, with the closing direction (13).
3. Die according to claim 1 or 2, characterised in that, in the moved-together end position of the die parts (9, 10), the secondary cavities (16, 17) are open towards the outside and/or are only partially filled with displaced material of the blank (15).
4. Die according to one of claims 1 to 3, characterised in that a respective secondary moulding part (18, 19) has first and second side faces (20, 21), of which the first side face abuts against an end face (23, 26) of one of the two die parts (9, 10) and of which the second side face (21) forms at least a portion of the wall bounding the respective secondary cavity (16, 17).
5. Die according to claim 4, characterised in that the first and second side faces (20, 21) of a respective secondary moulding part (18, 19) are connected to one another by way of an end face (22), which is drawn back from the main cavity (14) and forms a wall bounding the respective secondary cavity (16, 17).
6. Die according to claim 5, characterised in that the end face (22) of a respective secondary moulding part (18, 19) forms an angle of less than 45°, preferably of less than 20°, with the adjusting direction (29, 30) of a respective secondary moulding part.
7. Die according to one of claims 4 to 6, characterised in that the end face (23, 26) of the die part (9, 10) against which the first end face (20) of the respective secondary moulding part (18, 19) abuts has a portion which lies between the abutting region of the first side face (20) of the respective secondary moulding part (18, 19) and the moulding recess (11, 12) of the respective die part (9, 10) and which forms a wall bounding the respective secondary cavity (16, 17).
8. Die according to one of claims 1 to 7, characterised in that a first and a second secondary moulding part (18, 19) are provided, which are displaceably mounted on one of the die parts (10) on both sides of the moulding recess (12) of the die part (10).
9. Die according to one of claims 1 to 8, characterised in that, seen in cross section through the die, the second moulding recess (12) of the second die part (10) has an arcuate form.
10. Die according to one of claims 1 to 9, characterised in that, between a respective secondary moulding part (18, 19) and an end face (26) of one of the die parts (9), which is facing the other of the die parts (10), or between two secondary moulding parts (18, 18'; 19, 19'), which bound the same secondary cavity (16, 17), there is a gap, the width of which is reduced as the die parts (9, 10) are moved together.
11. Forging method for forging a portion having a toothing (5) of a toothed rack (4) for a steering device, wherein a blank (15) is shaped between two die parts (9, 10), of which the first die part (9) has a first moulding recess (11) for moulding the toothing (5) of the toothed rack (4), and the second die part (10) has a second moulding recess (12), which has the form of the back region of the toothed rack (4), lying opposite the toothing (5), and which can be moved together in a closing direction (13) from an open position into an end position (13), in which they are at a distance (s) from one another, while shaping the blank (15) placed into the die, wherein, in the region of the moulding recesses (11, 12) of the die parts (9, 10), there is formed between the die parts (9, 10) a main cavity (14), which in the moved-together end position of the die parts (9, 10) is open on opposite sides towards secondary cavities (16, 17), which respectively lie in a region lying between the first and second die parts (9, 10), and wherein, when the die parts (9, 10) move together, material of the blank (15) is displaced into the secondary cavities (16, 17), characterised in that the material displaced into the secondary cavities (16, 17) abuts against secondary moulding parts (18, 19), which respectively partially bound the flow of the displaced material in the respective secondary cavity (16, 17), and in that the material displaced into the secondary cavities (16, 17) is displaced into an intermediate space (42, 43), which is arranged within the respective secondary cavity (16, 17) and is bounded by a face (21) of the respective secondary moulding part (18, 19) that is directed in a direction of one of the die parts (10, 11) and the end face (26, 23) of the die part or by a face (21) of the respective secondary moulding part (18, 19) that is directed in the direction of one of the die parts (10, 11) and a surface of a further secondary moulding part (18', 19'), which is arranged in the same secondary cavity (16, 17) .
12. Forging method according to claim 11, characterised in that, in the moved-together end position of the die parts (9, 10), the secondary cavities are only partially filled with the displaced material of the blank (15).
13. Forging method according to claim 11 or 12, characterised in that, during the forging of the toothed portion of the toothed rack (4), the secondary moulding parts (18, 19) are kept stationary with respect to their adjusting directions (29, 30).
14. Forging method according to claim 11 or 12, characterised in that, during the forging of the toothed portion of the toothed rack (4), at least one of the secondary moulding parts (18, 19) is adjusted in an adjusting direction (29, 30).

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