Method and device for compression rolling a wheel blank, and vehicle wheel

Abstract

In order to form a radial undercut in the vicinity of the front rim flange on the inside of the rim of an integral vehicle wheel made of light metal during the compression rolling of a wheel blank of the vehicle wheel on a mandrel, it is proposed in the mandrel to use a slider device, around the radial outer edge of which the undercut is formed during the compression rolling and which is adjusted radially in the mandrel.

Description

[0001] Method and device for flow-forming a wheel blank and vehicle wheel

[0002] 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.

[0003] A vehicle wheel comprises a rim (also called 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 hole / wheel hub hole) and a wheel disc or a wheel rim (with spokes), whereby the wheel disc or wheel rim connects the wheel flange to the rim. When fitted to a vehicle, the wheel is placed on the wheel hub using the wheel hub hole 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 at a vehicle wheel axially, you can see a rim flange on the radially outer edge, which is the axial end of the rim. On the front side (outside, visible side) of the wheel is the front rim flange (outer flange) and on the back side (inside) of the wheel facing away from it is the rear rim flange (inner flange).The clear dimension 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. Axially immediately behind the rim flanges there 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, which prevents the tire from slipping into the rim.

[0004] A light-alloy wheel is usually made of an aluminum alloy, and less frequently 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.

[0005] 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 that is forged into a wheel. In the forging process, the wheel blanks are machined in several steps using hydraulic presses and thus gradually brought into the desired shape of the wheel.One processing step is flow forming, which is used to create 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, 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 known as 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 necessary. Otherwise, the formed rim contour can be mechanically post-processed.

[0006] During flow forming, the wheel blank is clamped between a spinning chuck, the outside 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 to 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 mandrel (a die), which are components of the spinning chuck.Through the radial pressing and axial movement of the spinning rollers, the material is compressed and stretched axially on the 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 guaranteed that after the wheel blank has been flow-formed, the rolled vehicle wheel or the rolled rim can be pulled off the clamping 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 clamping mandrel (the die) engages and which would prevent the flow-formed wheel from being demolded from the clamping mandrel by axial pulling after flow-forming, and that the rim and the clamping mandrel (the die) have a conical shape that tapers axially towards the wheel flange.

[0009] The production of a radial undercut on the radial inner side of the rim in the axially outer region of the rim during flow-forming of a wheel blank in order to reduce the wheel weight is therefore subject to considerable limitations according to the state of the art due to the requirement to be able to demold the wheel and the clamping 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 there is usually a comparatively large amount of wheel material, which also contributes significantly to the wheel's moment of inertia due to its large radial distance from the wheel axis.

[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 operation 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 region. This procedure is complex, can lead to stability and strength problems, impair the precise roundness of the wheel, create wheel imbalance, and does not allow the creation of an undercut on the radial inner side of the rim.

[0012] Based on this prior art, the present invention is based on the object of creating a method and a device with which a wheel with a reduced wheel weight can be produced after flow-forming. The same applies to the vehicle wheel.

[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 and 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 fed axially and radially from the outside to the wheel blank, has the special feature that when rolling out 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 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 that faces the placed wheel blank,and the slider 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 flow-forming of the rim, so that during the flow-forming it forms an abutment for the spinning roller on that axial region of the rim where the undercut is formed, and the slider device is retracted into the clamping mandrel after the flow-forming of the rim, 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 which 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 which 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 which faces 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 flow-forming of the rim, so that during the flow-forming it forms an abutment for the spinning roller on that axial region of the rim where the undercut can be formed, and the slider device is retractable into the clamping mandrel after the flow-forming of the rim, so that the vehicle wheel with the flow-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 according to the invention and / or a device according to the invention.

[0017] The invention has the advantage that when a wheel blank is flow-formed, a radial undercut can be formed on the radial inside of the rim in the axially outer region of the rim, which extends radially into the rim and in particular extends over the circumference of the rim in the rim material. This not only results in a reduced wheel weight, but by work hardening a wider outer wheel region by 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 which have a wide outer ring in the wheel rim for aerodynamic reasons, since 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 flow-formed, compacted material in the undercut area. With the invention, the separate subsequent machining step customary in the prior art for creating the undercut by turning (milling out) can be omitted. 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 production of the wheel blank by reducing its volume or weight accordingly.

[0018] The weight reduction of the vehicle wheel that can be achieved by an undercut produced according to the invention compared to a conventional standard cast wheel produced without an undercut can, for example, in the case of an 18-inch vehicle wheel, typically be between 0.4 kg and 1.2 kg.

[0019] 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 constructed and designed in such a way that the part of the clamping mandrel (the die) formed by it, in the open, radially outwardly extended position, forms a smooth, closed 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.

[0020] An advantageous feature of the method according to the invention can be that a wheel blank is flow-formed which has, on the axial inner side of the wheel rim, in a radially outer region facing the front rim flange, a depression in the material of the vehicle wheel, which depression extends axially and over at least part of the circumference of the wheel rim. Such a depression can be formed during forging or casting of the wheel blank before it is flow-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.

[0021] In a further development of the invention, the recess on the axial inner side of the wheel blank, in particular at the radial height of its rim base, can have or consist of an axial groove. The groove can be arranged axially in a region corresponding to the rim shoulder of the subsequent vehicle wheel. The groove can extend axially up to at most the axial height of the rim flange facing the recess.

[0022] Advantageously, the axial recess is designed in such a way that it forms a common, connected cavity with the radial undercut and widens the radial undercut in the axial direction. This makes it possible to achieve a particularly large reduction in the weight 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 enlarged as much as possible in the direction of the front rim flange, at least to the extent that the rough casting can be removed from the casting mold. By means of subsequent flow forming, the rim can be shaped radially inwards after the undercut has been formed, so that the rigidity of the rim can be increased by geometric edges (drop center).

[0023] Advantageously, in a device according to the invention it can be provided that the slide device comprises a plurality of slide segments which are arranged next to one another in the circumferential direction and are adjustable in the radial direction and whose radial outer sides 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 depression-free surface on its radial outer side. The adjustable slide segments preferably provide a closed, gap-free counter-bearing for the uniform formation of the undercut in the wheel blank when the wheel blank is formed 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 can, for example, have the approximate shape of circular segments, circular sectors or another shape, can be moved radially outwards for flow-forming the wheel in order to form, in the extended position, with their radial outer sides a surface that is closed over the circumference and free of gaps and depressions. After flow-forming, the slide segments can be retracted radially inwards, whereby when the slide device is retracted, the wide and narrow slide segments move radially inwards and the narrow slide segments move radially inwards by a greater distance than the wide slide segments.As the narrow slide segments free up the lateral gaps between the wider slide segments, the wide slide segments can move laterally towards one another and can be pushed together, so that the circumference of the slide device is reduced 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 clamping mandrel, i.e. pulled off in the axial direction. The actuating device for extending and retracting the slide segments can be designed in any suitable way, for example as an electrical, pneumatic or hydraulic device. Spring devices can also be used to assist or effect the extension and / or retraction of slide segments.

[0026] 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 is designed in such a way that when the actuating mandrel is axially displaced in an activation direction, the slide segments are radially extended and when the actuating mandrel is axially displaced 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 mandrel. Specifically, the slide segments are radially extended by the axial displacement of the actuating mandrel in the activation direction, and the slide segments are radially retracted by the axial displacement of the actuating mandrel 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.

[0027] According to an advantageous further development, it can be provided that the actuating mandrel 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 mandrel to bring about a radially directed movement of those slide segments which are connected to the actuating mandrel via a contact surface oriented obliquely to the wheel axis. The oblique contact surfaces convert, so to speak, an axial movement of the actuating mandrel into a radial movement of slide segments and vice versa. The slide segments, which are each non-positively connected to the actuating mandrel 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 connected in a force-locking manner to the actuating mandrel via a contact surface aligned obliquely to the wheel axis.

[0028] 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 spreading them apart, it can be provided in preferred embodiments,that only the narrow slide segments are each frictionally connected to the actuating mandrel via a contact surface aligned obliquely to the wheel axis. Upon axial displacement of the actuating mandrel in the activation direction, the narrow slide segments are then adjusted radially outward by means of the inclined contact surfaces, whereby the narrow slide segments slide between the wide slide segments, thereby spreading them apart and adjusting them outward.

[0029] According to a further advantageous embodiment of a device according to the invention, it can be provided that the actuating device comprises a hydraulic device for axially displacing the actuating mandrel in the activation direction. With a hydraulic device, both the displacement force required to displace the actuating mandrel in the activation direction can be applied and this can be triggered in a controlled manner when the slide segments are adjusted radially outward by the actuating mandrel, and the holding force required to hold the slide segments in the extended position can be applied when the vehicle wheel is flow-formed over the extended slide device.

[0030] The displacement of the actuating mandrel in the deactivation direction, which is arranged opposite to the activation direction, for the radial retraction of 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 and the slide segments are not hydraulically retracted, but that the actuating device comprises spring elements designed for the radial 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 only be arranged on the narrow slide segments, with the wide slide segments being reset in a different way, for example by 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 spring elements acting against it cause the slide segments to be reset.

[0031] 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 in the clamping mandrel. For stability reasons, the slide device is preferably adjusted in the extended position of its slide segments towards the clamping mandrel 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 enable easier demolding and / or to facilitate, enable, trigger, or assist the retraction of the slide device or the slide segments.

[0032] 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 at least part of 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 designed in the form of a groove.

[0033] The axial recess preferably has or consists of at least one axial groove on the axial inside of the vehicle wheel. The at least one axial groove can be arranged at the radial height of the rim well facing the recess. Axially, the axial groove can be arranged at the height of the front rim shoulder and / or the wheel rim facing the recess and / or extend at most up to the axial height of the front rim flange facing the recess. The groove can preferably project radially beyond the radial inside of the rim well. The groove can extend at least over part of the circumference of the wheel rim.

[0034] In an advantageous development of the invention, it can be provided that the axial groove together with the radial undercut forms a common cavity which is arranged at least partially, in particular completely, radially outside the radial inside of the rim base assigned to the recess. By means of the groove and / or the axial recess, the weight reduction achieved in this area can be combined with the undercut serving the same function in combination with the efficient manufacturing process of flow forming in order to obtain a wheel that is manufactured efficiently and at the same time has a reduced weight compared to conventional wheels. 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 special 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. The figures show:

[0035] Fig. 1 is an axial longitudinal section through a known vehicle wheel without radial undercut,

[0036] Fig. 2 is an axial longitudinal section through a vehicle wheel according to the invention of Fig. 1 with a radial undercut,

[0037] Fig. 3 shows a first embodiment of a radial undercut,

[0038] Fig. 4 shows a second embodiment of an undercut,

[0039] Fig. 5 shows a third embodiment of an undercut,

[0040] Fig. 6 is an axial longitudinal section through a device according to the invention with a vehicle wheel,

[0041] Fig. 7 shows the device of Fig. 6 in a different position,

[0042] Fig. 8 shows a slide device of a device according to the invention in the extended position, Fig. 9 shows the slide device of Fig. 8 in the retracted position,

[0043] Fig. 10 is an exploded view of the slide device of Fig. 9,

[0044] Fig. 11 is an axial longitudinal section through a device according to the invention with a vehicle wheel,

[0045] Fig. 12 is an axial longitudinal section through a device according to the invention in a first position in isometric perspective,

[0046] Fig. 13 shows the device of Fig. 12 in a second position,

[0047] Fig. 14 shows the device of Fig. 12 in a second position,

[0048] Fig. 15 shows the device of Fig. 12 in a third position,

[0049] Fig. 16 shows the device of Fig. 12 in a fourth position,

[0050] Fig. 17 a detail of Fig. 14,

[0051] Fig. 18 a detail of Fig. 16,

[0052] Fig. 19 shows the device of Fig. 12 in a fifth position,

[0053] Fig. 20 shows the device of Fig. 12 in a sixth position, Fig. 21 shows a further embodiment of the vehicle wheel according to the invention and the wheel blank associated therewith in a schematic section,

[0054] Fig. 22 shows a further embodiment of the vehicle wheel according to the invention and the wheel blank associated therewith in a schematic section and

[0055] Fig. 23 shows a further embodiment of the vehicle wheel according to the invention and the wheel blank associated therewith in a schematic section.

[0056] Fig. 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 ends with the front rim flange 6, and on the back 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 manufactured by forging or casting and the rim 2 was essentially formed by flow forming.

[0057] Within the meaning of the invention, it can be seen that there is a comparatively large amount of material in the area of ​​the front rim flange 6 of the vehicle wheel 1 or the rim shoulder 8 adjacent thereto. However, this is not significantly significant for the stability and strength of the vehicle wheel 1 and, due to its weight, has a detrimental effect on the driving characteristics. For this reason, efforts are made 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, by which material and weight are saved.

[0058] Fig. 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 prior art, a similar undercut 12 could in principle only be produced by machining the wheel 1 after the rim 2 has been flow-formed and the wheel 1 has been removed from the mandrel used in the flow-forming. According to the prior art, however, it is not possible to form such an undercut 12 during the flow-forming of the rim 2.

[0059] The reason for this is illustrated in Fig. 3, which shows a first embodiment of a radial undercut 12 according to the invention. This shows 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 limits the undercut 12 radially inwards. When the rim 2 is flow-formed according to the prior art, no radially projecting part of the clamping mandrel (the die) may project 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 region between the wheel rim 4 and .the spokes 5 and the rim 2 already during the flow forming of the rim 2 in order to save the otherwise necessary, subsequent, additional machining step of machining and to take into account the material savings achieved by the undercut 12 already in the design of the wheel blank.

[0060] Fig. 4 shows a second embodiment of an undercut 12 which 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 depression 14 in the material of the wheel 1 which extends axially and over the circumference of the wheel rim 4 in a radially outer region which faces the front rim flange 6. Fig. 4 shows two variants of the depression 14: In the first variant, the depression 14 extends approximately up to the radial height of the radial inside of the rim 2, which also corresponds to the radial height of the standard raw casting line 13. In the second variant, the depression 14 is radially widened by a groove 33, approximately up to the radial height of the radial outside of the rim 2. As a result, the standard raw casting line 13 assigned to this design of the recess 14 is also shifted radially outwards.The first variant of the recess 14 is shown separately in Fig. 21 and the second variant of the recess 14 in Fig. 23. Such a recess 14 can be formed during forging or casting of the wheel blank, before the wheel blank or its rim 2 is spin-formed, and enables an even greater reduction in weight 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 widens the radial undercut 12 in the axial direction. The standard raw casting line 13 is also shown. Fig. 5 shows a third embodiment of an undercut 12 in a modification of Fig. 4. As in Fig. 4, the axial recess 14 here also extends in the radial direction over the standard raw casting line 13 of the first variant of the recess 14 according to Fig. 4 inwards, particularly on the back of the spokes 5 .

[0061] 6 and 7 illustrate the basic principle of the invention. Fig. 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 placed thereon. The device 15 comprises a spinning chuck 17 with a clamping mandrel 18 for placing 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) which can be fed 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 out of the rim 2 and for this purpose has 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 which faces the attached wheel blank 16. The slide device 19 is radially adjustable in the clamping mandrel 18, namely, before the flow-forming of the rim 2, it can be extended in the radial direction out of the clamping mandrel 18, so that during the flow-forming it forms an abutment for the spinning roller on that axial region of the rim 2 on which the undercut 12 can be formed, and after the flow-forming of the rim 2, it can be retracted into the clamping mandrel 18, so that the vehicle wheel 1 with the flow-formed rim 2 can be removed from the clamping mandrel 18.

[0062] Fig. 6 shows the device 15 with the slider device 19 extended after the flow-forming of the rim 2. Because of the undercut 12 formed in the vehicle wheel 1 around the radial outer edge of the slider device 19 during the flow-forming, the vehicle wheel 1 cannot be pulled off the clamping mandrel 18 in this position of the slider device 19. As illustrated in Fig. 7, the slider 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.

[0063] 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 right next 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.

[0064] 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 clamping mandrel 18 without the vehicle wheel 1, the slide device 19 being extended in Fig. 8 and retracted in Fig. 9. As in the embodiment illustrated in Figs. 6 and 7, the slide device 19 of Figs. 8 to 10 is also axially adjustable in the clamping mandrel 18, i.e. it can perform an axial stroke in the clamping mandrel 18. As shown, the slide device 19 is preferably located directly on the clamping mandrel 18 in the radially extended position and is axially lifted slightly from the clamping mandrel 18 in the radially retracted position.This can enable easier demolding of the pressure-formed vehicle wheel 1 and / or facilitate, enable, trigger or assist the retraction of the slide device 19.

[0065] In Fig. 8 it can be seen that the slide device 19, in the extended position, forms a closed surface free of gaps and depressions on its radial outer side. The wheel blank 16 can be flow-formed on this surface precisely and without the formation of webs. The slide device 19 comprises a plurality of slide segments 20, 21, each arranged next 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 19. In the embodiment shown, 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.

[0066] When the slide device 19 is extended, the narrow slide segments 21 in the gaps between the wide slide segments 20 slide radially outwards and thereby press the wide slide segments 20 radially outwards and apart in a wedge-like manner. When the slide device 19 is retracted, the narrow slide segments 21 in the gaps between the wide slide segments 20 retract radially inwards and the wide slide segments 20 can also move radially inwards and towards one another. In the process, the circumference or the radial diameter of the slide device 19 decreases and it retracts radially from the undercut 12 formed during flow-forming.

[0067] An actuating device is used to extend and retract the slide segments 20, 21, which comprises an actuating mandrel 22 which can be displaced 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 embodiment of 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 when extending the slide segments 20, 21 and the direction of the deactivation movement 24 of the slide segments 20, 21 and the actuating mandrel 22 when retracting the slide segments 20, 21 are illustrated by the arrows shown in each case.

[0068] The actuating mandrel 22 is force-fittingly 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 force-fittingly connected to the actuating mandrel 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 like a wedge and radially outwards when the actuating mandrel 22 is moved axially in the activation direction. As a result, they slide radially into the gaps between the wide slide segments 20 and also push these apart like a wedge and radially outwards. For axially displacing the actuating mandrel 22 in the activation direction, the actuating device comprises a hydraulic device (not shown).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 in the activation direction is reduced, the spring elements 26 acting in the opposite deactivation direction cause the slide segments 20, 21 to automatically return to the retracted position.

[0069] In the exploded view of 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.

[0070] Fig. 11 shows an axial longitudinal section through a device 15 according to the invention corresponding to 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 removal of the vehicle wheel 1 upwards 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, can also be clearly seen here.

[0071] Figures 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 was described in Figures 8 to 10, for producing a one-piece vehicle wheel 1 made of light metal according to the invention.

[0072] The isometric axial longitudinal section of Fig. 12 shows the starting 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. Fig. 13 shows the next process step, in which the slide segments 20, 21 are radially extended from the clamping mandrel 18. For this purpose, the actuating mandrel 22 was pulled axially downwards, 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 the wide slide segments 20 were pushed apart in a wedge-like manner and radially outwards until the narrow slide segments 21 and wide slide segments 20 form a closed, gap- and depression-free surface on the radial outer side of the slide device 19 in the extended position 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.

[0073] Fig. 14 shows the next process step, in which a wheel blank 16 is placed on the device 15. The wheel blank 16 has previously been machined by forging, during which, 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 over the circumference 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 protruding axially downwards from the wheel blank 16. For this purpose, the counter chuck 30, which in Fig. 14 is not yet completely lowered onto the wheel blank 16, is lowered onto the wheel blank 16 and the wheel blank 16 is clamped between the spinning chuck 17 and the counter chuck 30.

[0074] In the next process step, which is illustrated in Fig. 15, the flow forming 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 protruding downwards from the wheel blank 16 (only one of which is shown), the rim 2 is rolled out of the round web protruding downwards from the wheel blank 16, with material thinning. Fig. 15 shows the position of the spinning roller 31 at the start and Fig. 16 its position at the end of the flow forming. The spinning roller 31 is guided axially downwards during the spinning process, whereby the material of the round web projecting downwards from the wheel blank 16 is pressed onto the clamping mandrel 18 and rolled out downwards.

[0075] The flow forming begins, viewed in the axial direction, very close axially behind the front rim flange 6, which results in advantageous 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. In Fig.

[0076] 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 flow forming and that the undercut 12 is formed on this abutment by flow forming with the spinning roller 31.

[0077] This can be seen even more clearly in the detailed views of Fig. 17 and Fig. 18. Fig. 17 shows, in a detail to Fig. 14, the position of the extended slider device 19 in the wheel blank 16 mounted on the device 15, still without undercut 12 before flow forming. Fig. 18 shows, in a detail to 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 that was formed around the radial outer edge of the slider device 19 by flow forming.

[0078] 16 and 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 pulled off 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 next process step illustrated in Fig. 19, the demolding of the flow-formed vehicle wheel 1 from the clamping mandrel 19 is therefore prepared by the slide segments 20, 21 of the slide device 19 being radially retracted.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, before or after this, the counter chuck 30 and the spinning roller 31 are removed.

[0079] Fig. 19 shows how the slide device 19, which is retracted radially into the clamping mandrel 18 after flow-forming, no longer engages in the radial undercut 12 formed during flow-forming, 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 illustrated in Fig. 20, in which the vehicle wheel 1 is half pulled upwards from the clamping mandrel 18. It can also be seen there that in some embodiments the slide device 19 is moved axially when the vehicle wheel 1 is demolded. After the finished flow-formed vehicle wheel 1 has been removed, the slide device 19 moves back to the starting position according to Fig. 12 and the device 15 is ready for flow-forming the next wheel blank 16.

[0080] Fig. 21 shows a vehicle wheel 1 according to the invention with the axial recess 14 on the axial inside, with a radial undercut 12 on the radial inside and the standard rough casting line 13 similar to the Fig. 4 and 5 already described, so that to avoid repetition reference is made to the relevant description. Overlaid with the vehicle wheel 1 is the wheel blank 32 thereof before the flow forming process, shown in dashed lines. This illustration shows that the wheel blank 32 already has the axial recess 14 on the axial inside, but not the radial undercut 12 on the radial inside which is only formed during the flow forming process according to the invention.

[0081] Fig. 22 shows a further embodiment of the vehicle wheel 1 according to the invention together with the wheel blank 32 assigned to it, similar to the illustration in Fig. 21. In contrast to the embodiment according to Fig. 21, the vehicle wheel 1, like its wheel blank 32, has an axial groove 33 as a depression 14 on the axial inside. The groove 33 extends over part of the circumference and is arranged radially approximately at the height of the rim well 2 of the vehicle wheel 1 and its wheel rim 4. Axially, the groove 33 is arranged at the height of the front rim shoulder 8 of the vehicle wheel 1, wherein the groove 33 does not extend axially up to the height of the front rim flange 6 facing the groove 33. The groove 33 of the finished vehicle wheel 1 forms, together with the radial undercut 12, a continuous cavity, which advantageously means a weight reduction of the vehicle wheel 1.

[0082] Fig. 23 shows a further embodiment of the vehicle wheel 1 according to the invention together with the wheel blank 32 assigned to it. Starting from the wheel blank 32 according to Fig. 21, the recess 14 on the axial inside was widened radially outwards by the groove 33 already described. Due to the process, the standard raw casting line 13 was thereby displaced radially outwards. During flow forming, the radial undercut 14 was produced which, together with the recess 14 and its groove 33, forms a connected cavity, as already described for Figs. 4 and 5.

Claims

Patent claims 1. A 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 in that 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 mandrel (18) which faces the attached wheel blank (16),and the slide device (19) for forming the undercut (12) is adjusted radially in the mandrel (18), wherein the slide device (19) before the pressing, rolling of the rim (2) is extended in the radial direction from the clamping mandrel (18) so that during the flow-forming process 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 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).

2. Method according to claim 1, characterized in that a wheel blank (16) is spin-formed, which has on the axial inner side of the wheel rim (4) in a radially outer region facing the front rim flange (6) a recess (14) in the material of the vehicle wheel (1) extending axially and over at least part of the circumference of the wheel rim (4).

3. Method according to claim 2, characterized in 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 axially and radially from the outside on A spinning roller (31) which can be fed onto the wheel blank (16) for rolling out the rim (2) of the vehicle wheel (1) while thinning the material, characterized in that 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 the rolling out 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), and the slide device (19) is radially adjustable in the clamping mandrel (18) for forming the undercut (12), wherein the slide device (19) is radially adjustable in the clamping mandrel (18) before the spinning of the rim (2) can be extended from the mandrel (18),so that during the flow-forming process it forms an abutment for the spinning roller (31) at that axial region of the rim (2) where 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 in that 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 in that the slide device (19) comprises a plurality of slide segments (20, 21) arranged side by side in the circumferential direction and 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 in 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 spread them apart.

8. Device (15) according to one of claims 6 or 7, characterized in that it has an actuating device for extending and retracting the slide segments (20, 21), which has a (17) in the axial direction of the mandrel (18) adjustable actuating mandrel (22) 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 in that the actuating mandrel (22) is force-lockingly 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 in that only each second slide segment (20, 21) in the circumferential direction is connected in a force-fitting manner 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 in that only the narrow slide segments (21) are each connected in a force-fitting manner 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 in 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 in that the actuating device comprises spring elements (26) which are designed for radially adjusting slide segments (20, 21) inwards.

14. Device (15) according to claim 13, characterized in that 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 in 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 in that the slide device (19) is axially adjustable in the clamping mandrel (18).

17. One-piece vehicle wheel (1) made of light metal, characterized in that it was spin-formed 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 in that the vehicle wheel (1) has on the axial inner side of the wheel rim (4) in a radially outer region facing the front rim flange (6) an axial recess (14) which extends in particular over at least part of the circumference of the wheel rim (4) and / or which together with the radial undercut (12) forms a common, continuous forms a cavity and expands the radial undercut (12) in the axial direction.

19. Vehicle wheel (1) according to claim 18, characterized in that the axial recess (14) on the axial Inside of the vehicle wheel (1) has or consists of at least one axial groove (33), wherein the at least one groove (33) is arranged in particular at the axial height of the front rim shoulder (8).

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