EP2598267A1

EP2598267A1 - Die for forging

Info

Publication number: EP2598267A1
Application number: EP11729382.9A
Authority: EP
Inventors: Jürgen DOHMANN; Christoph Westerkamp
Original assignee: ThyssenKrupp Presta AG
Current assignee: ThyssenKrupp Presta AG
Priority date: 2010-07-26
Filing date: 2011-07-02
Publication date: 2013-06-05
Anticipated expiration: 2031-07-02
Also published as: US9149860B2; PL2598267T3; BR112013001320A2; EP2598267B1; WO2012013284A1; CN103025453B; DE102010036609A1; BR112013001320B1; US20130192330A1; CN103025453A; DE102010036609B4; ES2575107T3

Abstract

The invention relates to a die for forging a toothed section of a gear rack of a steering device, comprising a first die part (9) having a first molding recess (11) for molding the toothing and a second die part (10) having a second molding recess (12), which has the shape of the back area of the gear rack opposite the toothing. The die parts (9, 10) can be moved toward each other in a closing direction (13) into an end position, in which the die parts have a distance (s) from each other, wherein a main cavity (14) is formed between the die parts (9, 10) in the region of the molding recesses (11, 12) of the die parts (9, 10), said main cavity being open on opposite sides to secondary cavities (16, 17), which lie in respective regions between the first and second die parts (9, 10). The die further includes at least two secondary molding parts (18, 19), which lie in respective regions between the first and second die parts (9, 10) and which at least partially form the walls that bound the secondary cavities and which can each be moved relative to the die parts (9, 10) in a setting direction (29, 30) oriented at an angle to the closing direction (13).

Description

Drop forge

The invention relates to a die for forging a toothed portion of a rack of a steering apparatus having first and second die parts, of which the first die part has a first die recess for forming the teeth of the rack and the second die part has a second die recess has the shape of the toothing of the opposite back region 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 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, each lying in a lying between the first and the second die part. 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 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 is disclosed in EP 0 738 191 B1 and the manufacture of this rack is carried out 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 some advantages over Y-section racks in manufacturing, even in their non-toothed areas, and in mounting or 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, particularly at the edges This leads to a strong material flow of the material of the blank under high pressure, which leads to heavy wear on the die parts, in particular on the edges of the die parts, which delimit the main cavity to the secondary cavities the achievable gearing accuracies are limited, which also depend on the burr geometry, which can only be changed by reworking the die parts themselves.

From EP 1 007 243 B1, a forging method with a burr for producing round sprockets with a burr is known, wherein the secondary cavities limit the flow of the blank material out of 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.

WO 2005/053875 A1 discloses a forging method without a burr for producing round sprockets. Between the two die parts two punches are provided. In the closed state of the two die parts, these are se 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 produces 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 having the features of claim 1 or by a forging method having 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 divide at least two minor 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 1 10 ° is preferred and a right angle to

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 material displaced into the secondary cavities flows to secondary moldings, which in each case partially limit the flow of the displaced material in the respective secondary cavity. 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 of 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. An "open" training of the secondary cavities in the above sense would also be present if the secondary cavities are closed in the end position of the die parts to the outside, but their volume is so large that it is not completely filled by the displaced material of the blank 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 2 mm.

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 next to the Formaus- perception) in their contracted end position.

The thickness of the secondary moldings (measured in the closing direction) is favorably at least a quarter, preferably at most three quarters, of the spacing of the mutually facing end faces of the die parts (in their sections adjacent to the mold cavities) when the die parts assume 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 Kulissenfüh- ments, 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.

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

Fig. 1 is a schematic representation of a steering device for a motor vehicle; Fig. 2 is an oblique view of a portion of the rack of the steering device (the toothed area shortened and simplified shown);

3 is a schematic representation of an embodiment of a die according to the invention in the open position, with inserted blank, in cross-section (at right angles to the longitudinal extent of the die or at right angles to the longitudinal axis of the rack).

4 shows a representation analogous to FIG. 3 during the collision of the two die parts;

5 is a view similar to Figure 3 in the contracted end position of the Gesenkenteile.

Fig. 6 is a view similar to Figure 3 after forging, the forged rack removed from the die.

Figs. 7 and 8 are side and top views of the rack after forging;

Figure 9 is a cross-section through the die in the collapsed end position of the two die parts, without the molded rack, for illustrative purposes; 10 to 13 are views similar to Figures 3 to 6 of a second embodiment of the invention.

FIG. 14 is a view similar to FIG. 5 of a third embodiment of the invention; FIG.

FIGS. 15 to 17 representations analogous to FIGS. 3 to 5 of a fourth embodiment of the invention;

FIG. 18 is a view similar to FIG. 5 of a fifth embodiment of the invention; FIG. FIG. 19 shows a representation analogous to FIG. 5 of a sixth embodiment of the invention.

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

Fig. 1 shows schematically 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 shown in Fig. 2 in an oblique view. The rack 4 has a portion with a toothing 5, which is shown in Fig. 2 for the sake of simplicity shortened. 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 parallel to its longitudinal axis 39 displacement direction 40, which in Fig. 2 by a double arrow is indicated.

The teeth 8 of the toothed portion are shown in Fig. 2 as a straight toothing 5 at equal intervals and the same tooth shapes. Frequently, deviating tooth geometries are to be used, whereby helical gears are used. can be seen. 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 shown in Fig. 3 schematically 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 form recess 1 1 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 collapsed end position is shown in Fig. 5 (with the rack 4 molded blank 15) and for further illustration in Fig. 9 (without a rack shaped blank 15). An inverse embodiment in which the first die part 9 is stationary and the second die part 10 is in a closing direction. tion (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 1 1, 12 lie, a main cavity 14 is formed, see. 9. The main cavity 14 thus comprises the regions of the mold recesses 11, 12 and the region lying between the mold recesses 11, 12 between the two die parts 9, 10. In FIG. 9, this is located between the mold recesses 11, 12 Area schematically delineated by dashed lines with respect to the side of the mold recesses 1 1, 12 lying areas that lie between the die parts 9, 10. The delimitations are shown here in FIG. 9 in a straight line between edges on the edges of the mold recesses 11, 12. 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 a main cavity 14 can also be seen in cross-section (corresponding to FIG. 9) of the mold space are limited by the mold cavities 1 1, 12 of the two Gesenkenteils 9, 10, in the position in which the two Gesenkenteils 9, 10 at Forming process are moved together closest together, as well as by the lines formed by the tangential extensions of the inner contours of the mold recesses 1 1, 12 of the respective die part 1 1, 12 beyond the associated edge 27, 28 and 24, 25 out to the intersection of this Tangential extensions, starting from the two die parts 9, 10. The exact course of delimitation, so whether, for example, the option shown in Fig. 9 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 can also be referred to as "burr gaps." The secondary cavities 16, 17 each lie within a region which lies between the two die parts 9, 10, and indeed these regions lie on both sides (with reference to FIGS aforementioned center plane) next to the mold cavities 1 1, 12th

In the between the die parts 9, 10 and on both sides of the mold recesses 1 1, 12 lying areas each have a separate secondary 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 1 1 of the first die part 9 are. 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 explained below with reference to FIGS. 3 to 6.

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 shown in Fig. 4. 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 is shown in FIG. 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

Rack 4 visible. The mold cavities 1 1, 12 of the die parts 9, 10 extending 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. In this case, a stop plate 34, 35, which lies between the directed away from the main cavity 14 end of a respective secondary 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 shown in FIGS. 10 to 13. 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 pages 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 FIG 1 and 12 can be seen.

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 enters here directly into the intermediate between the secondary mold parts 18, 19 and the (adjacent to the Formausnehnung 1 1 lying) end face 26 of the second Gesenkteils 9 intermediate spaces 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 explained with reference to FIGS. 15 to 17. The mounting of the secondary moldings 18, 19 corresponds to the first embodiment shown in FIGS. 3 to 9, but could for example also correspond to the embodiment shown in FIGS. 10 to 13. 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 also 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 clear from the comparison of FIGS. 16 and 17. 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 secondary moldings 18, 19 and the end face 26 of the die part 9.

In addition to the possibilities of optimization of the flow in the establishment of the forging process by different geometries of the secondary moldings 18, 19 can here optimizations by the positions and movements of the Nebenform- parts 18, 19 (which at least in this embodiment can also be referred to as stamps) are carried out 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, except for the shape of the mold cavity 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 considered

Rack are designated with triangular cross section.

FIG. 19 shows a sixth exemplary embodiment which, apart from the differences mentioned below, corresponds to the first exemplary 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 not shown in Fig. 19 for the sake of simplicity. 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 shaping recess forming the toothing is arranged in the movable die part 9. An arrangement in the fixed die part 10 is possible. As far as applicable or executable all different individual features of the various examples can be interchanged and / or combined without departing from the scope of the invention.

Legend

to the reference numbers

Steering wheel 22 end face

Steering shaft 23 end face

Steering pinion 24 edge

Rack 25 edge

Gearing 26 end face

Steering housing 27 edge

Tie rod 28 edge

Tooth 29 Adjustment direction first die part 30 Adjustment direction second die part 31 Edge

first mold recess 32 burr

second mold recess 33 ridge

Closing direction 34 stop plates

Main cavity 35 stop plates

Blank 36 stop

Nebenkavität 37 stop

Nebenkavität 38 projection

, 18 'secondary molding 39 longitudinal axis, 19' secondary molding 40 displacement direction, 20 'first side surface 41 course

, 21 'second side surface 42 gap

43 space

Claims

claims

1. die for forging a toothing (5) having portion of a rack (4) of a steering device with first and second die parts (9, 10), of which the first die part (9) has a first mold recess (1 1) for forming the toothing (5) of the rack (4) and the second die part (10) has a second mold recess (12) which has the shape of the toothing (5) opposite the back portion of the rack (4), and which under forming one in the die inserted blank (15), starting from an open position in a closing direction (13) are moved together into an end position in which they have a distance (s) from each other, wherein in the region of the mold recesses (1 1, 12) of the die parts (9, 10 ) between the die parts (9, 10) has a Hauptkavität (14) is formed, which is open in the collapsed end position of the Gesenkenteils (9, 10) on opposite sides to Nebenkavitäten (16, 17), which in each case in egg nem lying between the first and the second die part (9, 10) lying area, characterized in that the die further comprises at least two secondary moldings (18, 19), each lying in between the first and the second die part (9, 10) Are lying area and of which the Nebenkavitäten limiting walls are at least partially formed and each with respect to the die parts (9, 10) in an angularly to the closing direction (13) standing adjusting direction (29, 30) are displaceable.

2. Die according to claim 1, characterized in that the adjusting direction (29, 30) of the respective secondary molding (18, 19) with the closing direction (13) forms an angle of at least 45 °, preferably at least 70 °.

3. Die according to claim 1 or 2, characterized in that in the collapsed end position of the die parts (9, 10) Nebenkavitäten (16, 17) are open to 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, characterized in that a respective auxiliary part (18, 19) has first and second side surfaces (20, 21), of which the first side surface on an end face (23, 26) of the two Die parts (9, 10) rests and of which the second side surface (21) forms at least a portion of the respective Nebenkavität (16, 17) bounding wall.

5. Die according to claim 4, characterized in that the first and second side surface (20, 21) of a respective auxiliary molding (18, 19) via an end face (22) are interconnected, which is retreated relative to the main cavity (14) and a forms the respective Nebenkavität (16, 17) bounding wall.

6. Die according to claim 5, characterized in that the end face (22) of a respective auxiliary molding (18, 19) with the adjusting direction (29, 30) of a respective secondary molding part forms an angle of less than 45 °, preferably less than 20 ° ,

7. die according to one of claims 4 to 6, characterized in that the end face (23, 26) of the die part (9, 10) on which the first side surface (20) of the respective auxiliary molding (18, 19) is present, a portion comprising between the abutment region of the first side surface (20) of the respective secondary molding (18, 19) and the mold cavity (1 1, 12) of the respective die part (9, 10) and one of the respective Nebenkavität (16, 17) delimiting Wall forms.

8. Die according to one of claims 1 to 7, characterized in that a first and a second auxiliary molding (18, 19) are present, which at one of Sinked parts (10) are displaceably mounted on both sides of the mold recess (12) of this die part (10).

9. Die according to one of claims 1 to 8, characterized in that the second mold recess (12) of the second die part (10) seen in cross-section through the die has a circular arc shape.

10. Die according to one of claims 1 to 9, characterized in that between a respective secondary molding (18, 19) and an end face (26) of the die parts (9), which points to the other of the die parts (10), or between two Side moldings (18, 18 '; 19, 19') which delimit the same secondary cavity (16, 17) have a gap whose width decreases when the die parts (9, 10) move together.

1. A forging method for forging a section (5) of a toothed rack (4) for a steering device, wherein a blank (15) is formed between two die parts (9, 10), of which the first die part (9) is a first Mold recess (1 1) for forming the toothing (5) of the rack (4) and the second die part (10) has a second mold recess (12) which has the shape of the toothing (5) opposite the back region of the rack (4) , and which are moved together by forming the inserted into the die blank (15), starting from an open position in a closing direction (13) to an end position in which they have a distance (s) from each other, wherein in the region of the mold recesses ( 1 1, 12) of the die parts (9, 10) between the die parts (9, 10) a Hauptkavität (14) is formed in the collapsed end position of the die parts (9, 10) on opposite sides to Nebenkavi open (16, 17), which in each case lie in a region lying between the first and the second die part (9, 10), and in which the die parts (9, 10) move material of the blank (15) into the ne - Benkavitäten (16, 17) is displaced, characterized in that in the secondary cavities (16, 17) displaced material to secondary moldings (18, 19) starts, which in each case partially limit 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 forced into a gap (42, 43) within the respective secondary cavity (16, 17) is arranged and limited by a in the direction of one of the die parts (10, 1 1) directed surface (21) of the respective secondary molding (18, 19) and the end face (26, 23) of the die part or by a in Direction of the die parts (10, 1) directed surface (21) of the respective secondary molding (18, 19) and a surface of another secondary molding (18 ', 19') which is arranged in the same Nebenkavität (16,17).

12. Forging method according to claim 1 1, characterized in that the secondary cavities in the collapsed end position of the die parts (9, 10) are only partially filled with the displaced material of the blank (15).

13. forging method according to claim 1 1 or 12, characterized in that the secondary moldings (18, 19) during the forging of the toothed portion of the rack (4) relative to their actuating directions (29, 30) are held stationary.

14, forging method according to claim 1 1 or 12, characterized in that during the forging of the toothed portion of the rack (4) at least one of the secondary moldings (18, 19) in a setting direction (29, 30) is adjusted.

15. rack for a steering device of a motor vehicle, which is produced by the method according to any one of claims 1 1 to 14.