Method and apparatus for press rolling a wheel blank and vehicle wheel

Abstract

To form a radial undercut near the front rim flange on the inside of the rim of a one-piece light alloy vehicle wheel during the press rolling of a wheel blank on a mandrel, it is proposed to use a slide device in the mandrel, around whose radial outer edge the undercut is formed during press rolling and which is adjusted radially in the mandrel.

Description

[0001] The invention relates to a method and a device for flow-forming a wheel blank in the production of a one-piece vehicle wheel made of light metal, and to a one-piece vehicle wheel.

[0002] A vehicle wheel comprises a rim (also called the rim well; this is the radially outer part of the wheel on which a tire mounted on the wheel rests), a central wheel flange (with hole pattern / bolt circle, wheel connection surface and center bore / wheel hub bore) and a wheel disc or wheel rim (with spokes), whereby the wheel disc or wheel rim connects the wheel flange to the rim. When mounted on a vehicle, the wheel is placed on the wheel hub using the wheel hub bore and then fastened to the wheel hub using the holes in the hole pattern and wheel bolts, wheel studs or wheel nuts. If you look axially at a vehicle wheel, you can see a rim flange on the radially outer edge, which axially closes the rim. On the front (outside, visible side) of the wheel is the front rim flange (outer flange) and on the rear (inside) of the wheel, facing away from it, is the rear rim flange (inner flange).The clearance between the front and rear rim flanges is called the rim's internal width. The rim extends between the two rim flanges. A radially inward-facing depression in the rim is the drop center. Directly axially behind the rim flanges is a rim shoulder on which a tire bead of a tire mounted on the wheel can rest. The rim shoulders each have a hump extending axially inward, preventing the tire from slipping into the rim.

[0003] A light alloy wheel is usually made of an aluminum alloy, and less commonly of a magnesium alloy, and can be painted. A distinction is made between one-piece and multi-piece wheels. A one-piece wheel consists of a single piece of metal, whereas a multi-piece wheel is assembled from several pieces, e.g., bolted or welded together, such as a rim and wheel disc.

[0004] A one-piece vehicle wheel made of light metal can be manufactured by primary forming (casting) or by forming (forging). The manufacturing process has a significant influence on the properties of the wheel. When a wheel is manufactured by forging, a wheel blank is first produced. The wheel blank is a semi-finished product or preform of a wheel and is also referred to as a "rough casting", "billet" or "socket". Usually, a cast block is cast in the form of a cylindrical rod, which can be over 6 m long, and from this the wheel blank, i.e. a cylindrical rod section whose length is precisely tailored to the later wheel, is sawn or severed and then serves as the starting semi-finished product, which is forged into a wheel.

[0005] In the forging process, the wheel blanks are machined in several steps using hydraulic presses, gradually bringing them into the desired wheel shape. One processing step is flow forming, which creates the rim with its final internal width, usually together with the rear rim flange. The outer edge of the wheel blank is heated, and the entire rim area, from the outer to the inner flange, is rolled out. Flow forming is also known as flow spinning, flow (pressure) rolling, rotation rolling, stretch rolling, flow forming, or flow forming. The wheel blank is rolled on a mandrel under intense pressure and at temperatures of up to 400°C. The mandrel is also called a die. If the shell contour corresponds to the shape of the rim, no shape-changing mechanical post-processing of the formed rim contour is required.Otherwise, the formed rim contour can be reworked mechanically.

[0006] During flow forming, the wheel blank is clamped between a spinning chuck, the outer side of which is designed to form the rim, and a counter chuck that can be moved axially relative to the spinning chuck. The spinning chuck, the counter chuck and the clamped wheel blank are set in rotation and the rim is rolled out while the material is thinned by means of one or more spinning rollers (stretching rollers) that can be fed axially and radially from the outside onto the wheel blank. The spinning rollers are moved with radial pressure along the rotationally symmetrical circumference of the rotating wheel blank, i.e. with an axial movement component. On the inside, the material of the wheel blank is supported against the pressure of the spinning rollers, for example by means of a clamping mandrel (a die), which are components of the spinning chuck. The radial pressing and axial movement of the spinning rollers compacts the material and stretches it axially against the clamping mandrel (the die).

[0007] Flow forming saves material and reduces processing steps because less material needs to be removed from the wheel blank. Another major advantage of flow forming is the compaction of the metal, resulting in improved microstructure, improved elongation, and greater material stability.

[0008] When manufacturing vehicle wheels from light metal by forging, casting, and flow-forming, the aim is always to save material and to compress it. Saving material also leads to a reduced weight of the wheel, which has a positive effect on its handling. To reduce the amount of material and the weight of the wheel, it is known to create a radial undercut in the wheel material, for example in the area of ​​the front rim flange on the radial inside of the rim. However, such an undercut can only be produced in the vehicle wheel with great effort using the methods and devices known in the art. For example, by machining after flow-forming, or even without flow-forming in the case of a so-called monoblock wheel.This is because it must be ensured that after the wheel blank has been flow-formed, the rolled vehicle wheel or the rolled rim can be removed from the mandrel (the die). In practice, according to the state of the art, this means that no undercut can be formed in the rim during flow-forming into which a radially protruding part of the mandrel (the die) engages and would prevent the flow-formed wheel from being removed from the mandrel by axial removal after flow-forming, and that the rim and the mandrel (the die) have a conical shape that tapers axially toward the wheel flange.

[0009] The creation of a radial undercut on the radial inner side of the rim in the axially outer area of ​​the rim during flow-forming of a wheel blank to reduce the wheel's weight is subject to significant limitations according to the state of the art due to the requirement to be able to demold the wheel and the mandrel after flow-forming. Therefore, with conventional flow-forming, it is not possible to further optimize the area of ​​the wheel near the outer flange, where a comparatively large amount of wheel material is usually located and which, due to its large radial distance from the wheel axis, also contributes significantly to the wheel's moment of inertia.

[0010] To create a radial undercut on the radial inner side of the rim in the axially outer region of the rim, various approaches exist in the state of the art. A first possibility is to create the desired undercut by means of a rotary machining process after the spin-formed wheel has been removed from the mandrel (the die). This requires, on the one hand, an additional machining step and, on the other hand, a wheel blank that also contains the material to be removed in the rotary machining step.

[0011] WO 98 / 53937 discloses the creation of an undercut between the rim and the outer rim shoulder by splitting and forming the spin-formed wheel in the radial outer area. This procedure is complex, can lead to stability and strength problems, compromise the precise roundness of the wheel, create wheel imbalance, and does not allow for the creation of an undercut on the radial inner side of the rim.

[0012] Based on this prior art, the present invention seeks to provide a method and apparatus for producing a wheel with a reduced wheel weight after flow-forming. The same applies to vehicle wheels.

[0013] This object is achieved according to the invention by a method having the features of patent claim 1, by a device having the features of patent claim 4, and by a vehicle wheel having the features of claim 17. Embodiments, developments, and uses of the invention emerge from the dependent claims and the following description with associated drawings.

[0014] The method according to the invention for flow-forming a wheel blank in the production of a one-piece vehicle wheel made of light metal, wherein the wheel blank is placed on a clamping mandrel of a spinning chuck, the clamping mandrel is set in rotation with the wheel blank around the wheel axis, and the rim of the vehicle wheel is rolled out with material thinning by means of at least one spinning roller that can be advanced axially and radially from the outside to the wheel blank, has the special feature that, during the rolling out of the rim, a radial undercut is formed in the material of the vehicle wheel on the radial inside of the rim in an area facing the wheel rim. This is achieved by using a spinning chuck that has a slide device for forming the undercut, which is arranged in the clamping mandrel in the area of ​​the end of the clamping mandrel facing the mounted wheel blank, and the slide device is adjusted radially in the clamping mandrel to form the undercut.wherein the slider device is extended radially out of the clamping mandrel before the rim is flow-formed, so that during the flow-forming process it forms an abutment for the spinning roller at that axial region of the rim where the undercut is formed, and the slider device is retracted into the clamping mandrel after the rim has been flow-formed, so that the vehicle wheel with the flow-formed rim can be removed from the clamping mandrel.

[0015] The device according to the invention for flow-forming a wheel blank in the production of a one-piece vehicle wheel made of light metal, in particular for carrying out the method according to the invention, comprising a spinning chuck with a clamping mandrel for placing the wheel blank, a drive for rotating the clamping mandrel with the wheel blank around the wheel axis, and at least one spinning roller that can be fed axially and radially from the outside to the wheel blank for rolling out the rim of the vehicle wheel while thinning the material, has the special feature that the device is designed to form a radial undercut in the material of the vehicle wheel on the radial inside of the rim in an area facing the wheel rim during the rolling out of the rim and for this purpose has a spinning chuck that has a slide device for forming the undercut, which is arranged in the clamping mandrel in the area of ​​the end of the clamping mandrel facing the placed wheel blank,and the slider device for forming the undercut is radially adjustable in the clamping mandrel, wherein the slider device is extendable radially out of the clamping mandrel before the spin-forming of the rim, so that during the spin-forming it forms an abutment for the spinning roller at that axial region of the rim where the undercut can be formed, and the slider device is retractable into the clamping mandrel after the spin-forming of the rim, so that the vehicle wheel with the spin-formed rim can be removed from the clamping mandrel.

[0016] The one-piece vehicle wheel made of light metal according to the invention has the special feature that it was flow-formed using a method and / or a device according to the invention.

[0017] The invention has the advantage that, during the flow-forming of a wheel blank, a radial undercut can be formed on the radial inside of the rim in the axially outer region of the rim. This undercut extends radially into the rim and, in particular, extends over the circumference of the rim in the rim material. This not only reduces the wheel weight, but by work-hardening a wider outer wheel region through flow-forming, which can begin shortly after the front rim flange and include the area of ​​the hump there, the material properties are also improved in a wider region of the wheel. This applies in particular to vehicle wheels that have a wide outer ring in the wheel rim for aerodynamic reasons, as they have a large area in which rim material is concentrated.The invention thus combines the weight advantage of an undercut with the advantageous properties of pressure-formed, compacted material in the area of ​​the undercut.

[0018] With the invention, the separate subsequent machining step for creating the undercut by turning (milling out), which is common in the prior art, can be eliminated. This reduces both the equipment required and the machine cycle time. The volume of the undercut does not have to be removed from the rim by machining after flow-forming, but can be taken into account during the production of the wheel blank by reducing its volume or weight accordingly.

[0019] The weight reduction of the vehicle wheel achievable by an undercut produced according to the invention compared to a conventional standard cast wheel produced without an undercut can, for example, typically be between 0.4 kg and 1.2 kg for an 18-inch vehicle wheel.

[0020] According to an advantageous feature of the method and device according to the invention, it can be provided that the slide device, in the extended position, forms a closed, gap-free and depression-free surface on its radial outer side. The slide device is therefore advantageously designed or constructed such that the part of the clamping mandrel (the die) formed by it, in the open, radially outwardly extended position, forms a closed, smooth surface over its circumference on its radial outer side, i.e. on its surface which, during flow forming, faces the radial inner side of the rim or the radial outer side of the undercut, which surface has no gaps, depressions or elevations in the radial direction, so that the material of the wheel blank can be flow formed precisely on it.

[0021] An advantageous feature of the method according to the invention can be that a wheel blank is spin-formed which has a depression in the material of the vehicle wheel on the axial inner side of the wheel rim in a radially outer region facing the front rim flange, said depression extending axially and over the circumference of the wheel rim. Such a depression can be formed during forging or casting of the wheel blank before it is spin-formed. Such an axially extending depression in the wheel rim, which is formed in addition to the undercut extending radially in the rim, enables an even greater weight reduction of the vehicle wheel than the undercut alone. In preferred embodiments, such depressions are formed in spokes of the wheel rim. In these cases, they are also referred to as spoke pockets.

[0022] Advantageously, the axial recess is designed such that it forms a common, connected cavity with the radial undercut and widens the radial undercut in the axial direction. This allows a particularly significant weight reduction of the vehicle wheel in the area of ​​the front rim flange. An axial recess formed in the wheel blank during forging or casting in the rough casting, for example a spoke pocket, can thus be maximally enlarged in the direction of the front rim flange, at least to the extent that the rough casting can be removed from the mold. Through subsequent flow forming, after the undercut has been formed, the rim can be shaped radially inward, so that the rigidity of the rim can be increased through geometric edges (deep center).

[0023] Advantageously, a device according to the invention can be provided for the slide device to comprise a plurality of slide segments arranged adjacent to one another in the circumferential direction and adjustable in the radial direction, the radial outer sides of which are distributed over the circumference of the slide device. This can be provided, in particular, so that the slide device, in the extended position, forms a closed, gap-free, and recess-free surface on its radial outer side. The adjustable slide segments preferably provide a closed, gap-free counterbearing for uniformly forming the undercut in the wheel blank during forming of the wheel blank by flow-forming.

[0024] An advantageous further development of such a slide device can consist in that the slide device comprises wide slide segments and narrow slide segments, wherein the radial outer side of a wide slide segment covers a larger circumferential section of the slide device than the radial outer side of a narrow slide segment, the wide and narrow slide segments are arranged alternately next to one another in the circumferential direction and are in particular designed and radially adjustable by means of an actuating device such that when the slide device is extended, the wide and narrow slide segments move radially outwards, wherein the narrow slide segments can be moved radially outwards by a greater distance than the wide slide segments and can be moved between the wide slide segments and can spread them apart.

[0025] With a slide device designed in this way, the slide segments, which may, for example, have the approximate shape of circular segments, circular sectors, or another shape, can be moved radially outward for flow-forming the wheel. In the extended position, their radial outer sides form a circumferentially closed, gap- and recess-free surface. After flow-forming, the slide segments can be retracted radially inward. When the slide device is retracted, the wide and narrow slide segments move radially inward, and the narrow slide segments move radially inward by a greater distance than the wide slide segments.Because the narrow slide segments free up the lateral gaps between the wider slide segments, the wide slide segments can move laterally toward each other and can be pushed together, reducing the circumference of the slide device when the slide segments are retracted. As a result, after flow-forming, the slide device is pulled radially out of the radial undercut formed on its radial circumference during flow-forming, and the flow-formed vehicle wheel can be demolded from the mandrel, i.e., removed axially.

[0026] The actuating device for extending and retracting the slide segments can be designed in any suitable manner, for example, as an electric, pneumatic, or hydraulic device. Spring devices can also be used to assist or effect the extension and / or retraction of the slide segments.

[0027] A further advantageous feature of a device according to the invention can be that it has an actuating device for extending and retracting the slide segments, which comprises an actuating mandrel which is displaceable in the spinning chuck in the axial direction of the clamping mandrel and which is designed such that upon axial displacement of the actuating mandrel in an activation direction, the slide segments are radially extended and upon axial displacement of the actuating mandrel in the opposite deactivation direction, the slide segments are radially retracted.In this way, a radially directed movement of the slide segments can be effected by means of an axially directed actuation of the actuating pin. Specifically, the slide segments are extended radially by axially displacing the actuating pin in the activation direction, and the slide segments are retracted radially by axially displacing the actuating pin in the deactivation direction opposite to the activation direction. The activation direction can be arranged parallel to the axial direction and, in particular, correspond to it.

[0028] According to an advantageous further development, it can be provided that the actuating pin is non-positively connected to a plurality of slide segments, each via a contact surface oriented obliquely to the wheel axis. In this way, it is possible for an axially directed actuation of the actuating pin to cause a radially directed movement of those slide segments that are connected to the actuating pin via a contact surface oriented obliquely to the wheel axis. The oblique contact surfaces convert, so to speak, an axial movement of the actuating pin into a radial movement of slide segments and vice versa. The slide segments, each of which is non-positively connected to the actuating pin via a contact surface oriented obliquely to the wheel axis, can be all slide segments or, in preferred embodiments, only some slide segments.Such a preferred embodiment can consist in particular in that only each second slide segment in the circumferential direction is non-positively connected to the actuating mandrel via a contact surface aligned obliquely to the wheel axis.

[0029] In embodiments in which the slide device comprises wide and narrow slide segments, wherein the radial outer sides of the wide slide segments cover a larger circumferential section of the slide device than the narrow slide segments, the wide and narrow slide segments are arranged alternately next to one another in the circumferential direction and are designed and radially adjustable by means of an actuating device such that when the slide device is extended, the wide and narrow slide segments move radially outwards, wherein the narrow slide segments can be moved radially outwards by a greater distance than the wide slide segments and can be moved between the wide slide segments and can spread them apart, it can be provided in preferred embodiments that only the narrow slide segments are each non-positively connected to the actuating mandrel via a contact surface aligned obliquely to the wheel axis.When the actuating mandrel is moved axially in the activation direction, the narrow slide segments are then adjusted radially outwards by means of the inclined contact surfaces, whereby the narrow slide segments slide between the wide slide segments and thereby spread them apart and adjust them outwards.

[0030] According to a further advantageous embodiment of a device according to the invention, the actuating device can comprise a hydraulic device for axially displacing the actuating mandrel in the activation direction. A hydraulic device can be used to apply the displacement force required to displace the actuating mandrel in the activation direction and to trigger this displacement force in a controlled manner when the slide segments are moved radially outward by the actuating mandrel, as well as to apply the holding force required to hold the slide segments in the extended position when the vehicle wheel is pressure-formed over the extended slide device.

[0031] The displacement of the actuating mandrel in the deactivation direction, which is arranged opposite to the activation direction, for radially retracting the slide segments after flow-forming can also be carried out by means of a hydraulic device designed for this purpose. According to a preferred embodiment, however, it is proposed that the actuating mandrel is not hydraulically adjusted in the deactivation direction, nor are the slide segments hydraulically retracted, but rather that the actuating device comprises spring elements designed for radially inward adjustment of slide segments. These spring elements can be arranged, for example, on the actuating mandrel and / or on several or all slide segments.In the embodiment with wide and narrow slide segments, they can preferably be arranged only on the narrow slide segments, wherein the wide slide segments are reset in a different way, for example by means of drivers attached to the narrow slide segments for this purpose, i.e. the narrow slide segments have drivers for radially retracting the wide slide segments. In such embodiments, the axial displacement of the actuating mandrel in the deactivation direction or the retraction of the slide segments can then advantageously be triggered in a simple manner by reducing the actuating force applied by the hydraulic device provided for extending the slide segments to such an extent that the opposing spring elements cause the slide segments to reset.

[0032] According to an additional advantageous feature, the demolding of the spin-formed vehicle wheel from the clamping mandrel can be facilitated if the slide device is axially adjustable within the clamping mandrel. For stability reasons, the slide device is preferably adjusted toward the clamping mandrel in the extended position of its slide segments and can be pulled away from the clamping mandrel in the axial direction to remove the spin-formed vehicle wheel from the clamping mandrel, for example, to facilitate demolding and / or to facilitate, enable, trigger, or assist the retraction of the slide device or the slide segments.

[0033] Preferably, the vehicle wheel has an axial recess on the axial inner side of the wheel rim in a radially outer region facing the front rim flange, which extends in particular over the circumference of the wheel rim and / or which, together with the radial undercut, forms a common, continuous cavity and expands the radial undercut in the axial direction. The undercut and / or the axial recess can be configured as a groove.

[0034] Further advantages and features of the invention emerge from the claims and the following description, in which exemplary embodiments of the invention are explained in detail with reference to the drawings. The features described therein can be used individually or in combination to create preferred embodiments of the invention. Identical or equivalent parts are designated by the same reference numerals in the figures and are usually described only once, even if they can be advantageously used in other embodiments. They show: Fig. 1 an axial longitudinal section through a known vehicle wheel without radial undercut, Fig. 2 an axial longitudinal section through a vehicle wheel according to the invention of Fig. 1 with a radial undercut, Fig. 3 a first embodiment of a radial undercut, Fig. 4 a second embodiment of an undercut, Fig. 5 a third embodiment of an undercut, Fig. 6 an axial longitudinal section through a device according to the invention with a vehicle wheel, Fig. 7 the device of Fig. 6 in a different positioning, Fig. 8 a slide device of a device according to the invention in the extended position, Fig. 9 the slide device of Fig. 8 in the retracted position, Fig. 10 an exploded view of the slide device of Fig. 9, Fig. 11 an axial longitudinal section through a device according to the invention with a vehicle wheel, Fig. 12 an axial longitudinal section through a device according to the invention in a first position in isometric perspective, Fig. 13 the device of Fig. 12 in a second position, Fig. 14 the device of Fig. 12 in a second position, Fig. 15 the device of Fig. 12 in a third position, Fig. 16 the device of Fig. 12 in a fourth position, Fig. 17 a detail to Fig. 14, Fig. 18 a detail to Fig. 16, Fig. 19 the device of Fig. 12 in a fifth position and Fig. 20 the device of Fig. 12 in a sixth position.

[0035] In Fig. Figure 1 shows an axial longitudinal section through a known one-piece vehicle wheel 1 made of light metal without an undercut, which was produced by forging or casting and flow-forming a wheel blank. It comprises a rim 2 (also called rim well), a wheel flange 3, and a wheel rim 4 with spokes 5. On the front side of the vehicle wheel 1, the radially outer edge of the wheel rim 4 terminates with the front rim flange 6, while on the rear side of the vehicle wheel 1 is the rear rim flange 7. The rim 2 extends between the two rim flanges 6, 7. Axially immediately behind the rim flanges 6, 7 there is a rim shoulder 8, 9 with a hump 10, 11. The wheel rim 4 was essentially produced by forging or casting, and the rim 2 was essentially formed by flow-forming.

[0036] Within the meaning of the invention, it can be seen that a comparatively large amount of material is located in the area of ​​the front rim flange 6 of the vehicle wheel 1 or the adjacent rim shoulder 8. However, this is not significantly significant for the stability and strength of the vehicle wheel 1 and, due to its weight, adversely affects the driving characteristics. For this reason, the aim is to form a radial undercut in the material of the vehicle wheel 1 on the radial inner side of the rim 2 in an area facing the wheel rim 4, thereby saving material and weight.

[0037] Fig. Figure 2 shows an axial longitudinal section through a vehicle wheel 1 according to the invention, which, starting from the vehicle wheel of Fig. 1, is provided with such a radial undercut 12. According to the state of the art, a similar undercut 12 could in principle only be created by machining the wheel 1 after the rim 2 has been spin-formed and the wheel 1 has been removed from the mandrel used in the spin-forming process. However, according to the state of the art, it is not possible to form such an undercut 12 during the spin-forming of the rim 2.

[0038] The reason for this is explained by the Fig. 3 illustrates a first embodiment of a radial undercut 12 according to the invention. Shown is an axial section through a vehicle wheel 1 in the area of ​​the front rim flange 6. A dashed line also shows a standard raw casting line 13 which delimits the undercut 12 radially inwards. When flow-forming the rim 2 according to the prior art, no radially projecting part of the clamping mandrel (the die) may protrude radially outwards beyond the standard raw casting line 13, i.e. engage in the area of ​​an undercut 12 produced later by milling, since this would prevent the flow-formed wheel 1 from being demolded from the clamping mandrel by axial withdrawal after flow-forming. The invention is directed to providing such undercuts 12 in the radially inner transition area between the wheel rim 4 and the wheel rim 5.the spokes 5 and the rim 2 already during the flow forming of the rim 2 in order to save the subsequent, additional machining step of machining which would otherwise be required and to take into account the material savings achieved by the undercut 12 already in the design of the wheel blank.

[0039] The Fig. Figure 4 shows a second embodiment of an undercut 12 that can be formed by means of the invention. The vehicle wheel 1 shown therein has, in addition to the undercut 12 extending radially in the rim 2, also a recess 14 in the material of the wheel 1 that extends axially and over the circumference of the wheel rim 4 in a radially outer region facing the front rim flange 6. Such a recess 14 can be formed during forging or casting of the wheel blank, before the wheel blank or its rim 2 is flow-formed, and enables an even greater weight reduction of the vehicle wheel 1 than the undercut 12 alone. The axial recess 14 forms a common, connected cavity with the radial undercut 12 and expands the radial undercut 12 in the axial direction. The standard raw casting line 13 is also shown.

[0040] The Fig. 5 shows a variation of Fig. 4 a third embodiment of an undercut 12. As in Fig. 4, the axial recess 14 extends in the radial direction beyond the standard raw casting line 13 inwards, in particular on the back of the spokes 5.

[0041] The Fig. 6 and Fig. 7 illustrate the basic principle of the invention. In Fig. Figure 6 shows an axial longitudinal section through a device 15 according to the invention for flow-forming a wheel blank 16 produced by forging or casting during the production of a one-piece vehicle wheel 1 made of light metal with a vehicle wheel 1 mounted thereon. The device 15 comprises a spinning chuck 17 with a clamping mandrel 18 for mounting the wheel blank 16, a drive (not shown) for rotating the clamping mandrel 18 with the wheel blank 16 about the wheel axis, and at least one spinning roller (not shown here) that can be advanced axially and radially from the outside onto the wheel blank 16 for rolling out the rim 2 of the vehicle wheel 1 while thinning the material.The device 15 is designed to form a radial undercut 12 in the material of the vehicle wheel 1 on the radial inside of the rim 2 in a region facing the wheel rim 4 during rolling of the rim 2 and for this purpose has a spinning chuck 17 which, for forming the undercut 12, has a slide device 19 which is arranged in the clamping mandrel 18 in the region of the end of the clamping mandrel 18 which faces the attached wheel blank 16. The slide device 19 is radially adjustable in the clamping mandrel 18, namely, before the spin forming of the rim 2, it can be extended in the radial direction from the clamping mandrel 18, so that during the spin forming it forms an abutment for the spinning roller at that axial region of the rim 2 at which the undercut 12 can be formed, and after the spin forming of the rim 2, it can be retracted into the clamping mandrel 18, so that the vehicle wheel 1 with the spin formed rim 2 can be removed from the clamping mandrel 18.

[0042] The Fig. 6 shows the device 15 with the slider device 19 extended after the flow-forming of the rim 2. Due to the undercut 12 formed in the vehicle wheel 1 around the radial outer edge of the slider device 19 during the flow-forming process, the vehicle wheel 1 cannot be removed from the clamping mandrel 18 in this position of the slider device 19. As in Fig. 7, the slide device 19, which is retracted radially into the clamping mandrel 18 after the flow-forming, no longer engages in the radial undercut 12 formed during the flow-forming, so that the vehicle wheel 1 can be pulled off the clamping mandrel 18 in the axial direction despite the undercut 12.

[0043] The basic principle of the invention is therefore based on the use of a radially movable slide device 19, which serves as an abutment for the spinning rollers fed from the outside during the flow-forming process, which can begin already close to the front rim flange 6. This enables the realization of a radial undercut 12 in the rim 2 during flow-forming and a wider axial recess 14 in the area of ​​the wheel rim 4 when designing the wheel blank 16, whereby a reduced weight of the vehicle wheel 1 is achieved, but the vehicle wheel 1 can still be demolded from the clamping mandrel 18 after flow-forming. By implementing a movable slide device 19 in the spinning chuck 17 or the clamping mandrel 18 in an otherwise known flow-forming process, a vehicle wheel 1 with a large radial undercut 12 orwhen combined with an axial recess 14 with a large so-called “outer wheel pocket” formed by the undercut 12 and the recess 14, it can be formed with reduced manufacturing costs and shorter process times.

[0044] The Fig. 8 to 10 illustrate an example of a structural design of the slide device 19 of a device 15 according to the invention for realizing its radial adjustability. Fig. 8 and Fig. 9 show isometric sectional views of the slide device 19 in the mandrel 18 without vehicle wheel 1, wherein the slide device 19 in Fig. 8 extended and in Fig. 9. As in the Fig. 6 and Fig. 7, the slide device 19 of the Fig. 8 to 10 is also axially adjustable in the clamping mandrel 18, i.e., it can execute an axial stroke in the clamping mandrel 18. As illustrated, the slide device 19 is preferably located directly on the clamping mandrel 18 in the radially extended position and is axially slightly raised from the clamping mandrel 18 in the radially retracted position. This can enable easier demolding of the flow-formed vehicle wheel 1 and / or facilitate, enable, trigger, or assist the retraction of the slide device 19.

[0045] In Fig. 8 shows that the slide device 19, in the extended position, forms a closed, gap- and depression-free surface on its radial outer side. On this surface, the wheel blank 16 can be flow-formed precisely and without the formation of webs. The slide device 19 comprises a plurality of slide segments 20, 21, each arranged circumferentially adjacent to one another and adjustable in the radial direction, whose radial outer sides are distributed over the circumference of the slide device 19. In the illustrated embodiment, there are a total of twelve slide segments 20, 21. The slide segments 20, 21 are not identical in design, but comprise six wide slide segments 20 and six narrow slide segments 21. The radial outer sides of the wide slide segments 20 each cover a larger circumferential section of the slide device 19 than the narrow slide segments 21.The wide slide segments 20 and the narrow slide segments 21 are arranged alternately next to one another in the circumferential direction and are designed and radially adjustable by means of an actuating device such that when the slide device 19 is extended, the wide slide segments 20 and the narrow slide segments 21 move radially outwards, wherein the narrow slide segments 21 can be moved radially outwards by a greater distance than the wide slide segments 20 and can be moved between the wide slide segments 20 and can spread them apart.

[0046] When the slide device 19 is extended, the narrow slide segments 21 slide radially outward in the gaps between the wide slide segments 20, thereby pushing the wide slide segments 20 radially outward and apart in a wedge-like manner. When the slide device 19 is retracted, the narrow slide segments 21 retract radially inward in the gaps between the wide slide segments 20, and the wide slide segments 20 can also move radially inward and toward each other. In the process, the circumference or radial diameter of the slide device 19 decreases, and it retracts radially from the undercut 12 formed during flow-forming.

[0047] An actuating device is used to extend and retract the slide segments 20, 21, which comprises an actuating mandrel 22 which is displaceable in the spinning chuck 17 in the axial direction of the clamping mandrel 18. Upon axial displacement of the actuating mandrel 22 in an activation direction, which in the design of the Fig. 8 corresponds to an axial direction, the slide segments 20, 21 are extended radially and upon axial displacement of the actuating mandrel 22 in the deactivation direction opposite to the activation direction, the slide segments 20, 21 are retracted radially. The direction of the activation movement 23 of the slide segments 20, 21 and the actuating mandrel 22 upon extension of the slide segments 20, 21 and the direction of the deactivation movement 24 of the slide segments 20, 21 and the actuating mandrel 22 upon retraction of the slide segments 20, 21 are illustrated by the arrows.

[0048] The actuating pin 22 is non-positively connected to a plurality of slide segments 20, 21, each via a contact surface 25 oriented obliquely to the wheel axis. In the illustrated embodiment, only every second slide segment, and specifically only the narrow slide segments 21, is non-positively connected to the actuating pin 22 in the circumferential direction via a contact surface 25 oriented obliquely to the wheel axis. The oblique contact surfaces 25 cause the narrow slide segments 21 to be pushed apart in a wedge-like manner and radially outward upon axial movement of the actuating pin 22 in the activation direction. As a result, they slide radially into the gaps between the wide slide segments 20 and also push them apart in a wedge-like manner and radially outward. For axially displacing the actuating pin 22 in the activation direction, the actuating device comprises a hydraulic device (not shown).

[0049] In the illustrated embodiment, the slide segments 20, 21 are not retracted hydraulically; rather, the actuating device comprises spring elements 26, by means of which the slide segments 20, 21 are adjusted radially inward. These spring elements 26 are arranged only on the narrow slide segments 21. The wide slide segments 20 are returned from the extended to the retracted position by means of drivers 27 attached to the narrow slide segments 21. When the force applied by the hydraulic device for extending the slide segments 20, 21 and holding the slide segments 20, 21 in the extended position during flow-forming is reduced in the activation direction, the spring elements 26 acting in the opposite deactivation direction cause the slide segments 20, 21 to be automatically and independently returned to the retracted position.

[0050] In the exploded view of the Fig. 10 of the slide device 19 one can see the six wide slide segments 20, the six narrow slide segments 21, a guide ring 28 for the slide segments 20, 21, which are each guided radially adjustably by the guide ring 28 by means of a linear slide guide 29, two of the six spring elements 26, which are designed as compression springs acting on the narrow slide segments 21 and pressing the narrow slide segments 21 radially inwards, and some of the total of twelve drivers 27, which are each arranged on both sides of a narrow slide segment 21 and engage laterally in the wide slide segments 20.

[0051] The Fig. 11 shows an axial longitudinal section through a device 15 according to the invention corresponding to the Fig. 9, but with a vehicle wheel 1 placed thereon after it has been flow-formed by the device 15 and shortly before it is removed from the device 15. It can be seen here that the slide device 19, which is retracted from the radial undercut 12 formed during flow-forming, does not hinder the upward removal of the vehicle wheel 1 from the clamping mandrel 18. The contact surfaces 25, which are aligned obliquely to the wheel axis, between the actuating mandrel 22 and the narrow slide segments 21, which, upon axial movement of the actuating mandrel 22 in the activation direction (axially downwards in the illustrated embodiment), cause the narrow slide segments 21 to be adjusted radially outwards in a wedge-like manner, are also clearly visible here.

[0052] The Fig. 12 to 20 illustrate the process sequence during flow forming of a wheel blank 16 using a method according to the invention or using a device 15 according to the invention, which is shown in the Fig. 8 to 10, for the production of a one-piece vehicle wheel 1 made of light metal according to the invention.

[0053] In the isometric axial longitudinal section of the Fig. 12 shows the initial position of the slide device 19, in which the slide segments 20, 21 are radially retracted into the clamping mandrel 18 and the clamping mandrel 18 is placed on a spinning chuck 17. The Fig. 13 shows the next process step, in which the slide segments 20, 21 are extended radially from the clamping mandrel 18. For this purpose, the actuating mandrel 22 was pulled axially downward, whereby the narrow slide segments 21 were pushed apart in a wedge-like manner and radially outwards via the contact surfaces 25 aligned obliquely to the wheel axis, and in the process pushed the wide slide segments 20 apart in a wedge-like manner and radially outwards until the narrow slide segments 21 and wide slide segments 20, in the extended position of the slide device 19, form a closed, gap- and depression-free surface on the radial outer side of the slide device 19. The radial position of the slide device 19 or the slide segments 20, 21 is then fixed, for example, by the hydraulic control of the actuating mandrel 22 or by a fitting clamp of the actuating mandrel 22.

[0054] The Fig. Figure 14 shows the next process step, in which a wheel blank 16 is placed on the device 15. The wheel blank 16 was previously machined by forging, whereby, for example, the front rim flange 6, the wheel rim 4 with spokes 5, the wheel flange 3 and the recess 14 extending axially and circumferentially on the inside of the wheel rim 4 were formed. Using the device 15, the rim 2 and the rear rim flange 7 are formed from this wheel blank 16 by flow-forming the round web projecting axially downwards from the wheel blank 16. For this purpose, the counter chuck 30, which is in the Fig. 14 is not yet completely lowered onto the wheel blank 16, lowered onto the wheel blank 16 and the wheel blank 16 is clamped between the spinning chuck 17 and the counter chuck 30.

[0055] In the next process step, which is Fig. 15, the spinning of the wheel blank 16 begins. The spinning chuck 17, the counter chuck 30, and the clamped wheel blank 16 are set in rotation about the wheel axis by means of a drive (not shown). By means of one or more spinning rollers 31, which can be fed axially and radially from the outside onto the wheel blank 16 or onto the round web projecting downwards from the wheel blank 16 (only one of which is shown), the rim 2 is rolled out of the round web projecting downwards from the wheel blank 16, with material thinning. Fig. 15 shows the position of the pressure roller 31 at the beginning and the Fig. 16 maintains its position at the end of the flow-forming process. The flow-forming roller 31 is guided axially downward during the flow-forming process, whereby the material of the round web protruding downward from the wheel blank 16 is pressed against the clamping mandrel 18 and rolled downward.

[0056] The flow forming process begins very close to the front rim flange 6 in the axial direction, which results in a beneficial compaction of the material of the vehicle wheel 1 in this area. The geometric shape of the rim 2 is determined by the shape of the clamping mandrel 18. Due to the shape of the clamping mandrel 18, the rear rim flange 7 is also formed during the flow forming process. Fig. 16 it can also be seen that the slide device 19 formed by the slide segments 20, 21 and radially adjustable in the clamping mandrel 18 forms an abutment for the spinning roller 31 in the extended position during spinning and that the undercut 12 is formed on this abutment by spinning with the spinning roller 31.

[0057] This is shown in the detailed views of the Fig. 17 and Fig. 18 can be seen even more clearly. Fig. 17 shows in detail Fig. 14 the position of the extended slide device 19 in the wheel blank 16 mounted on the device 15, still without undercut 12 before flow forming. Fig. 18 shows in detail Fig. 16 the position of the extended slider device 19 in the vehicle wheel 1 mounted on the device 15, now with undercut 12 after flow forming of the wheel blank 16. In this position, the slider device 19 fills the undercut 12 which was formed around the radial outer edge of the slider device 19 by flow forming.

[0058] In the Fig. 16 and Fig. 18 it can be seen that due to the undercut 12 formed in the vehicle wheel 1 around the radial outer edge of the slide device 19 during flow forming, in the position of the slide device 19 shown there after flow forming, the vehicle wheel 1 could not be removed from the clamping mandrel 18 because the slide device 19 engages radially in the undercut 12 formed during flow forming and the flow-formed vehicle wheel 1 would get caught on the slide device 19 with the formed undercut 12 during axial removal from the clamping mandrel 19. In the Fig. 19, the next process step is therefore to prepare for demolding the flow-formed vehicle wheel 1 from the clamping mandrel 19 by radially retracting the slide segments 20, 21 of the slide device 19. For this purpose, the axial upward movement of the actuating mandrel 22 is released by the hydraulic device associated with actuating the actuating mandrel 22, so that the spring elements 26 acting on the narrow slide segments 21 press them radially inward. By means of the drivers 27 arranged on the narrow slide segments 21, the wide slide segments 20 are also pulled radially inward by the narrow slide segments 21, and by means of the inclined contact surfaces 25 between the narrow slide segments 21 and the actuating mandrel 22, the actuating mandrel 22 is pushed axially upward. During this time, before or after this, the counter chuck 30 and the spinning roller 31 are removed.

[0059] The Fig. 19 shows how the slide device 19, which is retracted radially into the clamping mandrel 18 after the flow forming process, no longer engages in the radial undercut 12 formed during the flow forming process, so that the vehicle wheel 1 can be pulled off the clamping mandrel 18 in the axial direction despite the formed undercut 12. This is shown in the Fig. 20, in which the vehicle wheel 1 is pulled halfway upwards from the clamping mandrel 18. It can also be seen there that in some embodiments, the slide device 19 is moved axially during demolding of the vehicle wheel 1. After removal of the finished, flow-formed vehicle wheel 1, the slide device 19 returns to the starting position according to Fig. 12 and the device 15 is ready for flow forming the next wheel blank 16. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 98 / 53937

[0011]

Claims

[1] Method for flow-forming a wheel blank (16) in the production of a one-piece vehicle wheel (1) made of light metal, wherein the wheel blank (16) is placed on a clamping mandrel (18) of a spinning chuck (17) and the clamping mandrel (18) with the wheel blank (16) is set in rotation about the wheel axis and the rim (2) of the vehicle wheel (1) is rolled out with material thinning by means of at least one spinning roller (31) which can be fed axially and radially from the outside to the wheel blank (16), characterized bythat during the rolling out of the rim (2) on the radial inside of the rim (2) in a region facing the wheel rim (4) a radial undercut (12) is formed in the material of the vehicle wheel (1) by using a spinning chuck (17) which has a slide device (19) for forming the undercut (12), which is arranged in the clamping mandrel (18) in the region of the end of the clamping mandrel (18) facing the attached wheel blank (16), and the slide device (19) is adjusted radially in the clamping mandrel (18) for forming the undercut (12), wherein the slide device (19) is extended in the radial direction out of the clamping mandrel (18) before the flow-forming of the rim (2) so that during the flow-forming it forms an abutment for the spinning roller (31) on that axial region of the rim (2) on which the undercut (12) is formed, and the slide device (19) is drawn into the clamping mandrel (18) after the pressure-forming of the rim (2),so that the vehicle wheel (1) with the pressure-formed rim (2) can be removed from the clamping mandrel (18). [2] Method according to claim 1, characterized by that a wheel blank (16) is spin-formed, which has a recess (14) in the material of the vehicle wheel (1) on the axial inner side of the wheel rim (4) in a radially outer region facing the front rim flange (6), which recess extends axially and over the circumference of the wheel rim (4). [3] Method according to claim 2, characterized by that the axial recess (14) forms a common, continuous cavity with the radial undercut (12) and widens the radial undercut (12) in the axial direction. [4] Device (15) for flow-forming a wheel blank (16) in the production of a one-piece vehicle wheel (1) made of light metal, in particular for carrying out a method according to one of claims 1 to 3, comprising a spinning chuck (17) with a clamping mandrel (18) for placing the wheel blank (16), a drive for rotating the clamping mandrel (18) with the wheel blank (16) around the wheel axis and at least one spinning roller (31) which can be fed axially and radially from the outside to the wheel blank (16) for rolling out the rim (2) of the vehicle wheel (1) while thinning the material, characterized by , that the device (15) for forming a radial undercut (12) in the material of the vehicle wheel (1) is designed on the radial inside of the rim (2) in an area facing the wheel rim (4) during rolling of the rim (2) and for this purpose a spinning chuck (17) which, for forming the undercut (12), has a slide device (19) which is arranged in the clamping mandrel (18) in the region of the end of the clamping mandrel (18) which faces the mounted wheel blank (16), and the slide device (19) for forming the undercut (12) is radially adjustable in the clamping mandrel (18), wherein the slide device (19) can be extended radially out of the clamping mandrel (18) before the flow-forming of the rim (2), so that during the flow-forming it forms an abutment for the spinning roller (31) on that axial region of the rim (2) on which the undercut (12) can be formed, and the slide device (19) can be retracted into the clamping mandrel (18) after the flow-forming of the rim (2), so that the vehicle wheel (1) with the flow-formed rim (2) can be removed from the clamping mandrel (18). [5] Device (15) according to claim 4, characterized bythat the slide device (19) in the extended position forms a closed, gap-free and recess-free surface on its radial outer side. [6] Device (15) according to one of claims 4 or 5, characterized by that the slide device (19) comprises a plurality of slide segments (20, 21) which are arranged next to one another in the circumferential direction and are adjustable in the radial direction, the radial outer sides of which are arranged distributed over the circumference of the slide device (19). [7] Device (15) according to claim 6, characterized byin that the slide device (19) comprises wide slide segments (20) and narrow slide segments (21), wherein the radial outer side of a wide slide segment (20) in each case covers a larger circumferential section of the slide device (19) than the radial outer side of a narrow slide segment (21), the wide slide segments (20) and the narrow slide segments (21) are arranged alternately next to one another in the circumferential direction and are in particular designed and radially adjustable by means of an actuating device such that when the slide device (19) is extended, the wide slide segments (20) and the narrow slide segments (21) move radially outwards, wherein the narrow slide segments (21) can be moved radially outwards by a greater distance than the wide slide segments (20) and can be moved between the wide slide segments (20) and can be moved so as to spread them apart. [8] Device (15) according to one of claims 6 or 7, characterized by in that it has an actuating device for extending and retracting the slide segments (20, 21), which comprises an actuating mandrel (22) which is displaceable in the spinning chuck (17) in the axial direction of the clamping mandrel (18), which is designed such that upon axial displacement of the actuating mandrel (22) in an activation direction, the slide segments (20, 21) are radially extended and upon axial displacement of the actuating mandrel (22) in the opposite deactivation direction, the slide segments (20, 21) are radially retracted. [9] Device (15) according to claim 8, characterized by that the actuating mandrel (22) is non-positively connected to a plurality of slide segments (20, 21) via a contact surface (25) aligned obliquely to the wheel axis. [10] Device (15) according to claim 9, characterized bythat only each second slide segment (20, 21) in the circumferential direction is non-positively connected to the actuating mandrel (22) via a contact surface (25) aligned obliquely to the wheel axis. [11] Device (15) according to claims 7 to 9, characterized by that only the narrow slide segments (21) are each non-positively connected to the actuating mandrel (22) via a contact surface (25) aligned obliquely to the wheel axis. [12] Device (15) according to one of claims 8 to 11, characterized by that the actuating device comprises a hydraulic device for axially displacing the actuating mandrel (22) in the activation direction. [13] Device (15) according to one of claims 8 to 12, characterized by that the actuating device comprises spring elements (26) which are designed for the radial inward adjustment of slide segments (20, 21). [14] Device (15) according to claim 13, characterized bythat the spring elements (26) are arranged only on the narrow slide segments (21). [15] Device (15) according to one of claims 7 to 14, characterized by that the narrow slide segments (21) have drivers (27) for radially retracting the wide slide segments (20). [16] Device (15) according to one of claims 4 to 15, characterized by that the slide device (19) is axially adjustable in the clamping mandrel (18). [17] One-piece vehicle wheel (1) made of light metal, characterized by that it was pressure-rolled using a method according to one of claims 1 to 3 and / or a device (15) according to one of claims 4 to 16. [18] Vehicle wheel (1) according to claim 17, characterized bythat the vehicle wheel (1) has an axial recess on the axial inner side of the wheel rim (4) in a radially outer region facing the front rim flange (6), which recess extends in particular over the circumference of the wheel rim (4) and / or which, together with the radial undercut (12), forms a common, connected cavity and widens the radial undercut (12) in the axial direction.

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