Method and mold for producing a wheel for a motor vehicle

Abstract

Method for producing a wheel (12) for a motor vehicle by die casting, in which a melt (18) is introduced into a cavity (30) of a casting mold (10), wherein the melt (18) passes from a hub (34) of the wheel (12) via a wheel disc (38) of the wheel (12) to a rim base (36) of the wheel (12), and wherein in the produced wheel (12) a passage opening (46) of the hub (12) to a visible side (40) of the wheel (12) can be covered by means of a hub cap (58), characterized in that at least a part of the melt (18) is directed via an annular sprue cross-section (64) which is formed on the visible side (40) of the wheel (12) and which, in the produced wheel (12) provided with the hub cap (58), extends in the radial direction over an outer edge (60) of the hub cap (58) and runs circumferentially around the outer edge (60) of the hub cap (58), is introduced into the cavity (30) of the casting mold (10),wherein this part of the melt (18) is introduced into the cavity (30) from outside a diameter (70) of the passage opening (46) and thus from the visible side (40) of the wheel (12), and wherein a further part of the melt (18) is introduced into the cavity (30) of the casting mold (10) via an inner peripheral region (72) of the passage opening (46), which borders on the annular sprue cross-section (64) towards a rotation axis (68) of the wheel (12).

Description

[0001] The invention relates to a method for producing a wheel for a motor vehicle by die casting, in which a molten material is introduced into a cavity of a casting mold. The molten material flows from a hub of the wheel via a wheel disc of the wheel to a rim well of the wheel. In the produced wheel, a through-opening of the hub towards a visible side of the wheel can be covered by a hub cap. Furthermore, the invention relates to a casting mold for producing a wheel for a motor vehicle using a die casting process.

[0002] DE 10 2020 100 704 A1 describes a method for producing a motor vehicle rim made of an aluminum alloy for a wheel of a motor vehicle. The method provides that the motor vehicle rim is produced in one piece and continuously in a casting mold by die-casting a casting material, wherein the casting mold has outlet openings through which casting material can exit the casting mold.

[0003] DE 10 2020 100 702 A1 describes a method for producing a motor vehicle rim made of aluminum, in which a casting material is introduced into a casting tool. By introducing the casting material into the casting tool by means of die casting, a hub, a rim center, and a rim well of the motor vehicle rim are produced, with the rim center connecting the hub to the rim well. The die casting can be carried out as vacuum die casting.

[0004] DE 10 2016 106 256 B3 describes a device for producing cast parts or rims for motor vehicles using a low-pressure casting process.

[0005] DE 10 2006 036 369 B4 describes a process for the production of components by integrated melting, casting and forming.

[0006] Cast wheels for motor vehicles are typically manufactured using a low-pressure casting process, also known as permanent mold casting. In this process, a comparatively low pressure of less than 10 bar is applied to a molten mass, causing the molten mass to rise into a permanent mold. Mold filling, i.e., filling a cavity formed in the mold or permanent mold with the molten mass, occurs comparatively slowly in low-pressure casting and can therefore take several seconds up to approximately 30 seconds.

[0007] Due to the comparatively high mold temperature and the comparatively long solidification time, low-pressure casting can achieve effective mold filling, even if the melt enters the cavity via a comparatively small sprue cross-section, where the wheel is formed as the melt solidifies. However, design freedom is limited in low-pressure casting for the production of wheels for motor vehicles or other automobiles, particularly with regard to the creation of delicate spokes with thin walls.

[0008] An alternative die-casting process is vacuum die casting, in which the cavity is subjected to a negative pressure or evacuation, and the melt is introduced into the mold cavity at a higher pressure than in low-pressure casting. In vacuum die casting, the melt is also subjected to very high pressure or holding pressure after the cavity has been filled, particularly at a pressure in the range of 350 bar to 1,000 bar.

[0009] With vacuum die casting, it is important to ensure that the mold filling process, i.e., the introduction of the molten metal into the mold cavity, is completed very quickly, especially within a period of less than 150 milliseconds. Otherwise, the molten metal may solidify in the area of ​​the mold wall before the filling process is complete. However, vacuum die casting enables the production of wheels with a high degree of design freedom and thin walls, as well as particularly delicate spoke designs.

[0010] The object of the present invention is to provide a method of the type mentioned at the outset, in which a particularly rapid filling of the cavity of the casting mold with the melt can be achieved, and to create a corresponding casting mold designed to carry out the method.

[0011] This object is achieved by a method having the features of patent claim 1 and by a casting mold having the features of patent claim 9. Advantageous embodiments with expedient further developments of the invention are specified in the dependent patent claims and in the following description.

[0012] In the method according to the invention for producing a wheel for a motor vehicle by die casting, a melt is introduced into a cavity of a casting mold. The melt flows from a hub of the wheel via a wheel disc of the wheel to a rim base of the wheel. In the manufactured wheel, a passage opening of the hub leading to a visible side of the wheel can be covered by a hub cap. At least a portion of the melt is introduced into the cavity of the casting mold via an annular sprue cross-section formed on the visible side of the wheel, with this portion of the melt being introduced into the cavity from outside a diameter of the passage opening and thus from the visible side of the wheel. In the manufactured wheel provided with the hub cap, the annular sprue cross-section extends radially beyond an outer edge of the hub cap.In other words, the outer circumference of the annular sprue cross-section is larger than the outer circumference of the hub cap at its outer edge. Furthermore, the annular sprue cross-section extends circumferentially around the outer edge of the hub cap when the hub cap is attached to the wheel in the manufactured wheel.

[0013] In the method according to the invention, a further portion of the melt is introduced into the mold cavity via an inner circumferential region of the passage opening. The inner circumferential region borders the annular sprue cross-section toward a rotational axis of the wheel. By using the inner circumferential region of the passage opening, in addition to the annular sprue cross-section formed on the visible side of the wheel, to introduce the melt into the mold cavity, a particularly large cross-section through which the melt flows is provided when filling the cavity.

[0014] The use of both the inner circumferential area of ​​the passage opening and the annular sprue cross-section to introduce the melt into the mold cavity in the die-casting process is therefore particularly advantageous. This applies in particular when the inner circumferential area and the annular sprue cross-section merge seamlessly. In this configuration, a continuous flow front is preferably formed across the inner circumferential area of ​​the passage opening and the annular sprue cross-section, along which the melt is introduced in the die-casting process or during die casting into the region of the mold cavity in which the wheel is formed.

[0015] The inner circumferential region of the passage opening, which is also used for introducing the melt into the cavity of the casting mold, is preferably formed in an end region of the passage opening close to the visible side of the wheel and is formed as the inner side of a wall of the hub, this wall of the hub delimiting the passage opening in the circumferential direction.

[0016] By utilizing the annular surface of the sprue cross-section for introducing the melt into the cavity, a particularly large cross-section is provided through which the pressurized melt can flow. This allows for very rapid filling of the mold cavity with the melt. In other words, mold filling time can be significantly reduced compared to a process in which a smaller cross-section is available for introducing the melt into the mold cavity, in which the wheel of the motor vehicle, particularly a motor vehicle, is formed due to the solidification of the melt.

[0017] In this way, a particularly high casting quality can be achieved for the wheel produced using the die-casting process, because the mold cavity can be completely filled with the melt even in a very short period of time. Even a comparatively large-volume wheel can therefore be produced with high quality using the die-casting process.

[0018] The provision of the annular sprue cross-section formed in the hub area is based on the realization that an asymmetrical sprue system, in which the melt is not fed centrally from the wheel hub but rather from the outside into the cavity, is not effective. This is because such a sprue system, in which the melt is not fed centrally from the wheel hub, cannot achieve a satisfactory level of reproducible quality across the entire wheel. However, the latter is achievable due to the use of the annular sprue cross-section to introduce at least part of the melt into the mold cavity.

[0019] The use of the annular sprue cross-section to introduce at least part of the melt into the mold cavity also makes it possible to achieve particularly low dosing or filling weights. Accordingly, a comparatively small mass of melt is sufficient to completely fill the cavity and the sprue system, wherein the wheel comprising the hub, the wheel disc, and the rim base is formed in the cavity due to the solidification of the melt. In particular, because the melt is introduced centrally from the wheel hub into the cavity, the sprue system using the annular sprue cross-section advantageously has a smaller volume than is the case with sprue systems in which the melt is not fed axially and centrally from the wheel hub, but rather radially from the outside or from the side.This makes it possible to manufacture or produce the bike in a very resource-saving and energy-efficient manner.

[0020] In addition, a die-casting machine, which applies pressure to the melt to force it into the mold cavity, can be kept particularly small. This is especially true when a three-platen tool technique is used to prepare the mold. This involves a first, fixed platen, a second, movable platen, and a third, also movable platen, which are used to prepare the mold. This allows the wheel to be manufactured particularly cost-effectively or with high efficiency.

[0021] Furthermore, a great deal of design freedom allows for the incorporation of design elements into the wheel, which can be particularly delicate. In particular, comparatively delicate and / or sharp-edged spokes can be formed in the area of ​​the wheel disc, with the spokes connecting the wheel hub to the rim well.

[0022] A light metal melt, such as an aluminum alloy and / or a magnesium alloy, or the like, can be used as the melt. This, as well as the provision of delicate spokes in the area of ​​the wheel disc, is advantageous in terms of the wheel's low weight. Furthermore, by completely filling the cavity with the melt, a high degree of wheel strength can be achieved. This is especially true if a die-cast material is used to provide the melt, which is high-strength after solidification or after solidification and an optional heat treatment.

[0023] The finished wheel can be connected to a wheel hub of the motor vehicle or motor vehicle via the hub, which has the through-opening. For this purpose, the wheel can be bolted to a flange of the wheel hub. In particular, the hub can be placed onto an extension of the wheel hub, with the extension protruding into the through-opening of the wheel hub. When the wheel is attached to the wheel hub of the motor vehicle, the visible side or outer side of the wheel is visible to an observer standing next to the motor vehicle.

[0024] Likewise, an outer side or visible side of the hub cap is visible to the observer if the hub cap is attached to the wheel and the opening of the hub towards the visible side of the wheel is covered or concealed by the hub cap.

[0025] The hub cap can interact, in particular, by means of at least one locking element with a corresponding locking element provided on the wheel side. For example, a locking lug can be used as such a locking element formed on the wheel side, which is engaged behind by the at least one locking element of the hub cap when the hub's through-opening on the visible side of the wheel is covered by the hub cap.

[0026] Preferably, the wheel is produced using a vacuum die-casting process, in which the cavity is subjected to a negative pressure via at least one outlet opening of the casting mold during and / or before the melt is introduced into the cavity. The use of the vacuum die-casting process is advantageous with regard to a desirably rapid filling of the cavity with the melt. In particular, by providing a high speed with which a piston introducing the melt into the cavity is moved and by subjecting the cavity to the negative pressure via at least one outlet opening of the casting mold, it can be achieved that the mold filling, i.e. the filling of the cavity with the melt, is completed in less than 150 milliseconds, preferably in less than 100 milliseconds.This is particularly advantageous because it ensures that the melt only solidifies once the filling process is complete.

[0027] In particular, in the vacuum die casting process, flow velocities of the melt in the range of approximately 50 meters per second to approximately 100 meters per second can occur in a sprue channel of the casting mold, through which the melt is conveyed to the annular sprue cross-section.

[0028] Furthermore, in the vacuum die casting process, the melt in the mold cavity can be subjected to a pressure ranging from approximately 350 bar to approximately 1,000 bar. This pressure is thus significantly higher than the pressure prevailing in low-pressure casting, which is typically only a few bar and usually less than 10 bar.

[0029] However, even when using the vacuum die casting process, the speed of a piston used to force the melt into the mold, as well as the flow velocity of the melt in the sprue cross-section, cannot be increased indefinitely. This is due to the characteristics of the die-casting machine used in vacuum die casting or the vacuum die casting process. Especially with a large wheel diameter and thus a larger amount of melt to fill the cavity, it is therefore a challenge to achieve mold filling times in the range of less than 150 milliseconds, and especially less than 100 milliseconds.

[0030] Therefore, it is particularly advantageous when manufacturing the wheel in the vacuum die casting process if the melt is introduced into the cavity of the casting mold both via the annular sprue cross-section and via the inner circumferential area of ​​the passage opening.

[0031] Preferably, after removal from the mold, the wheel is machined in the area of ​​the annular sprue cross-section using a cutting process. This can give the annular sprue cross-section a visually appealing appearance.

[0032] In particular, a design element can be created on the wheel in the area of ​​the annular sprue cross-section using the chip-cutting process. This ensures that, despite the use of the annular sprue cross-section for introducing the melt into the casting mold, this sprue area formed on the visible side of the wheel does not detract from the wheel's visual appearance. In fact, the visual appearance of the wheel is actually enhanced by the chip-cutting or chip-removing machining in the area of ​​the annular sprue cross-section.

[0033] Turning, in particular, can be used as a machining process. This allows for a very precise design of the design element. Additionally or alternatively, the area of ​​the annular sprue cross-section can be machined using milling and / or grinding.

[0034] Preferably, an annular groove is produced on the wheel removed from the casting mold using the machining process. After the hub cap has been attached to the wheel, this annular groove radially borders on or reaches the outer edge of the hub cap. Alternatively, the annular groove can be partially covered by an outer edge region of the hub cap. In the circumferential direction, the annular groove runs around the outer edge of the hub cap. The provision of such a channel-shaped depression in the region of the annular sprue cross-section ensures, on the one hand, a visually appealing design of this partial region of the wheel. In addition, the provision of the annular groove leads to a reduction in the mass of the wheel, which is advantageous with regard to a desirable low weight of the wheel.

[0035] To create the hub's passage opening, a pin element associated with the casting mold is preferably used, which has an extension. The extension, which is particularly designed in the manner of a counter-pin, projects into the melt, which is pressed into the cavity. The extension projects beyond the annular sprue cross-section, counter to the flow direction of the melt and toward the visible side of the wheel. Such a pin element can achieve particularly good flow onto the annular sprue cross-section. This is especially true if the pin element is rotationally symmetrical with respect to the wheel's axis of rotation.

[0036] Furthermore, the provision of the pin element allows for a particularly high flow velocity in the area of ​​the wheel's gate, i.e., where the component to be manufactured, in the form of the wheel, begins in the cavity filling with the melt. This is also advantageous with regard to the rapid filling of the cavity with the melt.

[0037] During die casting, the melt preferably flows over a rounded, free end of the extension. This allows for particularly low-friction and unhindered flow of the melt over the extension.

[0038] Additionally or alternatively, it can be provided that the melt is deflected during die casting at a transition from the extension to a base region of the pin element arranged within the passage opening by means of a rounded portion of the pin element in a radial direction toward the annular sprue cross-section. This also contributes to a particularly largely unobstructed flow of the melt toward the annular sprue cross-section.

[0039] Preferably, the annular sprue cross-section is provided with a substantially constant width in the radial direction. This allows for a very uniform filling of the mold cavity with the melt flowing through at least the annular sprue cross-section in the die-casting process.

[0040] Preferably, a plurality of spokes are formed in the area of ​​the wheel disc. This is advantageous in terms of low weight and good shock absorption by the wheel.

[0041] Preferably, the spokes are manufactured with a wall thickness of approximately 2 mm to approximately 10 mm. Such comparatively delicate and / or sharp-edged spokes, in particular, can be produced with particularly high process reliability by die casting, in which the annular sprue cross-section is utilized to introduce at least part of the melt into the mold cavity.

[0042] While a low-pressure casting process can only produce spokes with a comparatively large wall thickness, in particular with a wall thickness in the range of approximately 10 mm to approximately 25 mm, in the present case the spokes are preferably produced with a wall thickness of less than 5 mm.

[0043] The casting mold according to the invention is designed for producing a wheel for a motor vehicle using a die-casting process. A melt can be introduced into a cavity of the casting mold. A wheel hub, a wheel disc connecting the hub to a wheel rim, and the wheel rim can be provided through respective, connected partial regions of the cavity. In the produced wheel, a through-opening of the hub toward a visible side of the wheel can be covered by a hub cap. At least a portion of the melt can be introduced into the cavity of the casting mold via an annular sprue cross-section formed on the visible side of the wheel. This portion of the melt can be introduced into the cavity from outside a diameter of the through-opening and thus from the visible side of the wheel.Another portion of the melt can be introduced into the mold cavity via an inner circumferential region of the passage opening, which borders the annular sprue cross-section toward a rotational axis of the wheel. In the manufactured wheel equipped with the hub cap, the annular sprue cross-section extends radially beyond an outer edge of the hub cap. Furthermore, in the manufactured wheel equipped with the hub cap, the annular sprue cross-section runs circumferentially around the outer edge of the hub cap.

[0044] Using such a casting mold, the cavity of the casting mold can be filled with the melt particularly quickly. Accordingly, the casting mold is designed to carry out the method according to the invention.

[0045] In particular, the casting mold can be designed as a three-plate casting tool comprising a stationary first platen, a movable second platen, and a likewise movable third platen. Using such a casting mold, it is particularly possible to achieve a lower pressure during the casting process in the region of a parting surface where the second movable platen faces the third movable platen than would be the case with a two-plate tool or a two-plate casting mold with otherwise identical die-casting process parameters.

[0046] The advantages and preferred embodiments described for the method according to the invention also apply to the casting mold according to the invention and vice versa.

[0047] The invention therefore also includes further developments of the inventive casting mold that have features already described in connection with the further developments of the inventive method. For this reason, the corresponding further developments of the inventive casting mold are not described again here.

[0048] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0049] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 shows a highly schematic representation of a casting mould for producing a wheel for a motor vehicle, which is subjected to a melt in a vacuum die-casting process; Fig. 2 section of the casting mould according to Fig. 1 manufactured wheel, wherein a sprue element in the region of a hub of the wheel is still connected to the wheel; Fig. 3 partial and schematic view of the wheel according to Fig. 2 after removal of the sprue element, wherein a passage opening of the hub of the wheel towards a visible side of the wheel is covered by a hub cover; Fig. 4 schematically shows a plan view of an annular groove formed in the region of an annular sprue cross-section of the wheel, which extends in the radial direction to an outer edge of the hub cap and runs in the circumferential direction around the outer edge of the hub cap; Fig. 5 shows a section of the wheel during the casting process and an enlarged detail in the area of ​​the wheel hub; Fig. 6 shows a partial and schematic view of a variant of the die-casting process in which only a partial area of ​​an inner circumference of the passage opening of the hub is used to introduce melt into a cavity of the casting mold; Fig. 7 shows a section of a central area of ​​the wheel encompassing the hub, with the hub cap locked in the through-opening of the hub; and Fig. 8 shows a highly schematic sectional view of the wheel, which includes the hub, a wheel disc and a rim base.

[0050] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0051] In the figures, the same reference symbols designate elements with the same function.

[0052] In Fig. 1 schematically shows a casting mold 10 as used for producing a Fig. 8, which can also be used to create a wheel 12 for a motor vehicle, which is also shown in a highly schematic manner. A vacuum die-casting process is used to produce the wheel 12 in the casting mold 10. A piston 14 presses a melt 18 provided in a melting furnace 16 into the casting mold 10.

[0053] In the example in Fig. 1, a three-plate tool technique is used. Accordingly, the casting mold 10 comprises a first, stationary or fixed platen 20 and a second, movable platen 22. At a first parting surface 24, when the casting mold 10 is closed, the first platen 20 and the second platen 22 adjoin one another. Analogously, when the casting mold 10 is closed, the second, movable platen 22 adjoins a third, likewise movable platen 28 of the casting mold 10 in the region of a second parting surface 26. The second platen 22 and the third platen 28 define a cavity 30 into which the melt 18 is forced under high pressure by means of the piston 14 during the vacuum die-casting process. Furthermore, the casting mold 10 can comprise, in a manner not shown in detail here, a plurality of slides, which can participate in delimiting or forming the cavity 30.

[0054] The casting mold 10 has at least one outlet opening 32, through which the cavity 30 can be subjected to a negative pressure. By applying the negative pressure to the at least one outlet opening 32 and due to the high pressure with which the piston 14 presses the melt 18 into the cavity 30, a particularly rapid filling of the cavity 30 with the melt 18 can be achieved in the vacuum die-casting process. Due to the solidification of the melt in the cavity 30 of the casting mold 10, the wheel 12 is formed, which in Fig. 8 is shown in a very schematic sectional view.

[0055] According to Fig. 8, the wheel 12 comprises, in a manner known per se, a hub 34 and a wheel disc 38 connecting the hub 34 to a rim well 36 of the wheel 12, as well as the rim well 36. Towards a visible side 40 or outer side of the wheel 12, the rim well 36 ends with an outer flange 42 or outer rim flange, which can also be referred to as the front rim flange. In other words, the rim well 36 of the wheel 12 extends in the axial direction towards the visible side 40 up to the outer flange 42. In the opposite direction, the rim well 36 is delimited by an inner flange 44, which can also be referred to as the inner rim flange or rear rim flange.

[0056] The hub 34 of the wheel 12 has a through-opening 46, into which, for example, a pin-like extension of a wheel hub (not shown) of the motor vehicle can be inserted in order to connect the wheel 12 to the wheel hub in a rotationally fixed manner. A bolt circle or hole ring can encircle the hub 34, with individual holes 48 of the bolt circle being arranged, for example, in Fig. 2. By screwing wheel nuts or similar fastening elements into the holes 48 of the bolt circle, the wheel 12 can be fixed to the wheel hub (not shown) of the motor vehicle, which in this case is designed as a motor vehicle. Fig. 8 with Fig. 2 it is further apparent that the wheel disc 38 of the wheel 12 may be formed by a plurality of spokes 50 which connect the hub 34 to the rim base 36.

[0057] In Fig. 2, the wheel 12 or a blank of the wheel 12 is partially shown after the solidification of the wheel 12 in the cavity 30 of the casting mold 10 (compare Fig. 1) and after removal from the casting mold 10. Here, the wheel 12 is still formed in one piece with a sprue element 52, which is to be removed from the blank to complete the wheel 12, for example by a machining process, such as turning.

[0058] During the vacuum pressure casting, during which the cavity 30 of the casting mold 10 is filled with the melt 18, the melt 18 flows at high speed through a sprue 54 formed in the casting mold 10, which is shown schematically in Fig. 1. Through a section 56 of the runner 54 adjacent to the finished wheel 12 (compare Fig. 1) is used in the Fig. 2 shown blank of the wheel 12 or intermediate product in the manufacture of the wheel 12, the sprue element 52 is formed.

[0059] In Fig. 3, the wheel 12 is shown in detail and after removing the sprue element 52 (compare Fig. 2) in a view of the visible side 40 or outside. Here, the through opening 46 of the hub 34 (compare Fig. 8) is covered towards the visible side 40 of the wheel 12 by means of a hub cap 58. The hub cap 58 has an outer edge 60 or outer rim.

[0060] In Fig. 3 also shows an annular groove 62, which is formed on the visible side 40 of the wheel 12 and which, after the hub cap 58 has been attached to the wheel 12, can extend radially to the outer edge 60 of the hub cap 58 or can be partially or partially covered by an outer edge region of the hub cap 58. After the hub cap 58 has been attached to the wheel 12, this annular groove 62 runs around the outer edge 60 of the hub cap 58 in the circumferential direction of the wheel 12.

[0061] The annular groove 62 is produced in the present case after removal of the wheel 12 or the blank of the wheel 12, which is still formed integrally with the sprue element 52, from the casting mold 10 in the region of an annular sprue cross-section 64. An approximate position of the annular sprue cross-section 64 is shown in Fig. 5 is shown in a detailed enlargement, which is a schematic representation of a section of the blank of the wheel 12 located in the casting mold 10. The annular sprue cross-section 64 is according to Fig. 5 on the visible side 40 or outside of the wheel 12.

[0062] When the hub cap 58 is attached to the finished wheel 12 and the through-opening 46 of the hub 34 is covered towards the visible side 40 of the wheel 12 by means of the hub cap 58, the annular sprue cross-section 64 extends in the radial direction beyond the outer edge 60 of the hub cap 58. In the circumferential direction, the annular sprue cross-section 64 or the annular groove 62 formed here runs around the outer edge 60 of the hub cap 58 (cf. Fig. 7).

[0063] By using the annular sprue cross-section 64 to introduce the melt 18 into the cavity 30 of the casting mold 10, particularly short mold filling times can be achieved when filling the cavity 30 for the purpose of producing the wheel 12.

[0064] The process of rapidly introducing the melt 18 into the cavity 30 during vacuum die casting will be described below with reference to Fig. 5. Here, the section 56 of the runner 54 is shown, through which the melt 18 flows during the filling of the cavity 30. A flow direction 66 of the melt 18 as it flows through the section 56 of the runner 54 is shown in Fig. 5 illustrated by an arrow.

[0065] Furthermore, in Fig. 5 shows a rotation axis 68 of the wheel 12, of which in Fig. 5 only the hub 34 and parts of the spokes 50 are shown schematically. Furthermore, in Fig. 5 a diameter 70 of the passage opening 46 of the hub 34 is illustrated by a double arrow.

[0066] Out of Fig. 5 it is further apparent that a part of the melt 18 is introduced into the cavity 30 from outside the diameter 70 of the passage opening 46 and thus from the visible side 40 or design side of the wheel 12. In addition, according to Fig. 5 an inner peripheral region 72 of the passage opening 46 is used to introduce a further part of the melt 18 into the cavity 30 of the casting mold 10.

[0067] The position or extent of this inner circumferential region 72 of the hub 34, via which the melt 18 is introduced into the cavity 30, is in Fig. 5 in an enlarged detailed view of a section of the hub 34 of the wheel 12. From this detailed enlargement, in conjunction with Fig. 4 further shows that the inner circumferential region 72 used for casting or as a sprue cross-section on the one hand and the annular groove 62 on the other hand form an outer end of the finished wheel 12.

[0068] In Fig. 6 schematically illustrates the conditions that would arise if only the inner circumference of the passage opening 46 of the hub 34 were used to introduce the melt 18 into the cavity 30 of the casting mold 10. Two lines 74 running parallel to the rotation axis 68 illustrate the sprue cross-section through which the melt 18 can flow in the region of the hub 34.

[0069] In contrast, Fig. 5 by two lines 76 aligned obliquely to the rotation axis 68, the cross section through which the melt 18 flows, enlarged compared to the parallel lines 74, is illustrated when the melt 18 is introduced into the cavity 30 of the casting mold 10.

[0070] Furthermore, Fig. 5 by further auxiliary lines 78 perpendicular to the rotation axis 68, through which the melt 18 can flow, within the section 56 of the runner 54. Auxiliary lines 80 corresponding to these auxiliary lines 78 from the position in the section 56 of the runner 54 are also shown in Fig. 6. From a comparison of Fig. 5 with Fig. 6 it is immediately apparent that the Fig. 5 are consistently longer than the vertical auxiliary lines 80 corresponding to these auxiliary lines 78, which are shown in Fig. 6 are shown.

[0071] Accordingly, the Fig. 5, enlarged gate cross-sections are provided because not only the inner circumferential area 72 of the passage opening 46 is used to introduce the melt 18 into the cavity 30, but also the annular gate cross-section 64 (compare Fig. 5), on which, after removing the sprue element 52 from the hub 34 of the wheel 12, the annular groove 62 (compare Fig. 7) is trained.

[0072] In order to ensure a very rapid filling of the cavity 30 of the casting mold 10 in the vacuum pressure casting process, it is therefore not sufficient to cast the wheel 12 only in the area of ​​the inner cross section of the hub cap or the hub cover 58, as is shown in Fig. 6. Rather, in the present case, the sprue area of ​​the wheel 12 is preferably supplemented, in addition to the inner cross section or the inner circumferential area 72, by an annular surface on the design side or visible side 40 of the wheel 12, wherein the additional, annular sprue cross section 64 is provided by this annular surface (cf. Fig. 5).

[0073] After casting the wheel 12, the annular groove 62 is produced in the area of ​​this annular sprue cross-section 64 (compare Fig. 4 and Fig. 7), preferably by a machining process, such as turning. In this process, a design element of the wheel 12, such as the annular groove 62, is created. The hub cap 58 can then be centrally positioned within this annular groove 62 on the finished wheel 12.

[0074] Out of Fig. 5 further shows that a pin element 86 belonging to the casting mold 10 can be used to produce the passage opening 46 of the hub 34, which pin element has an extension 88. The extension 88 projects into the melt 18, which due to the pressure exerted by the piston 14 (see Fig. 1) applied pressure into the cavity 30. According to Fig. 5, the extension 88 projects beyond the annular sprue cross-section 64 towards the visible side 40 of the wheel 12, opposite to the flow direction 66 of the melt 18.

[0075] During die casting, the melt 18 flows around a rounded free end 90 of the extension 88, which projects into the section 56 of the sprue 54. At a transition of the extension 88 to a foot region 94 of the pin element 86 arranged within the passage opening 46, the melt is deflected in the radial direction toward the annular sprue cross-section 64 by means of a rounded partial region 92 of the pin element 86.

[0076] Out of Fig. 7 it is evident that the hub cap 58 can have a plurality of locking elements 82, which engage behind at least one locking lug 84 corresponding to these locking elements 82, which is provided on the side of the hub 34 of the wheel 12. In Fig. 7, only one of these locking elements 82 is shown engaging behind the locking lug 84. Furthermore, according to Fig.7 the hub cover 58 has a clamping ring 86 which applies a spring force acting in the radial direction to the locking elements 82.

[0077] Overall, the examples show how an improved gating system can be provided for manufacturing wheels 12 in the die casting process.

Claims

[1] Method for producing a wheel (12) for a motor vehicle by die casting, in which a melt (18) is introduced into a cavity (30) of a casting mold (10), wherein the melt (18) passes from a hub (34) of the wheel (12) via a wheel disc (38) of the wheel (12) to a rim base (36) of the wheel (12), and wherein in the wheel (12) produced, a passage opening (46) of the hub (12) to a visible side (40) of the wheel (12) can be covered by means of a hub cover (58), characterized bythat at least a part of the melt (18) is introduced into the cavity (30) of the casting mold (10) via an annular sprue cross-section (64) which is formed on the visible side (40) of the wheel (12) and which, in the wheel (12) produced and provided with the hub cover (58), extends in the radial direction beyond an outer edge (60) of the hub cover (58) and runs in the circumferential direction around the outer edge (60) of the hub cover (58), wherein this part of the melt (18) is introduced into the cavity (30) from outside a diameter (70) of the passage opening (46) and thus from the visible side (40) of the wheel (12), and wherein a further part of the melt (18) is introduced via an inner circumferential region (72) of the passage opening (46), which extends towards a rotation axis (68) of the wheel (12) to the annular sprue cross-section (64) is introduced into the cavity (30) of the casting mold (10). [2] Method according to claim 1, characterized bythat the wheel (12) is produced in a vacuum die-casting process in which the cavity (30) is subjected to a negative pressure via at least one outlet opening (32) of the casting mold (10) during and / or before the melt (18) is introduced into the cavity (30). [3] Method according to one of the preceding claims, characterized by that the wheel (12) is machined in the region of the annular sprue cross-section (64) by means of a chip-cutting process after being removed from the casting mould (10). [4] Method according to claim 3, characterized bythat an annular groove (62) is produced on the wheel (12) removed from the casting mold (10) by the chip-cutting process, which annular groove (62) adjoins the outer edge (60) of the hub cover (58) in the radial direction after the hub cover (58) has been attached to the wheel (12) or is at least partially covered by an outer edge region of the hub cover (58), and which runs in the circumferential direction around the outer edge (60) of the hub cover (58). [5] Method according to one of the preceding claims, characterized by in that, to produce the passage opening (46) of the hub (34), a pin element (86) belonging to the casting mold (10) is used, which pin element has an extension (88), wherein the extension (88) projects into the melt (18) which is pressed into the cavity (30), and wherein the extension (88) projects beyond the annular sprue cross-section (64) against a flow direction (66) of the melt (18) and towards the visible side (40) of the wheel (12). [6] Method according to claim 5, characterized by that the melt (18) flows over a rounded free end (90) of the extension (88) during the die casting and / or is deflected in the radial direction towards the annular sprue cross-section (64) by means of a rounded partial region (92) of the pin element (86) at a transition of the extension (88) to a foot region (94) of the pin element (86) arranged within the passage opening (46). [7] Method according to one of the preceding claims, characterized by that the annular sprue cross-section (64) is provided with a substantially constant width in the radial direction. [8] Method according to one of the preceding claims, characterized bythat a plurality of spokes (50) of the wheel (12) are formed in the region of the wheel disc (38), wherein the spokes (50) are produced with a wall thickness of approximately 2 mm to approximately 10 mm, in particular with a wall thickness of less than 5 mm. [9] Casting mold for producing a wheel (12) for a motor vehicle in a die-casting process, wherein a melt (18) can be introduced into a cavity (30) of the casting mold (10), wherein a hub (34) of the wheel (12), a wheel disc (38) of the wheel (12) connecting the hub (34) to a rim well (36) of the wheel (12), and the rim well (36) can be provided through respective, connected partial areas of the cavity (30), and wherein in the produced wheel (12), a passage opening (46) of the hub (34) towards a visible side (40) of the wheel (12) can be covered by means of a hub cover (58), characterized bythat at least a part of the melt (18) can be introduced into the cavity (30) of the casting mold (10) via an annular sprue cross-section (64) which is formed on the visible side (40) of the wheel (12) and which, in the wheel (12) produced and provided with the hub cover (58), extends in the radial direction beyond an outer edge (60) of the hub cover (58) and runs in the circumferential direction around the outer edge (60) of the hub cover (58), wherein this part of the melt (18) can be introduced into the cavity (30) from outside a diameter (70) of the passage opening (46) and thus from the visible side (40) of the wheel (12), and wherein a further part of the melt (18) can be introduced via an inner circumferential region (72) of the passage opening (46), which extends to a rotation axis (68) of the wheel (12) towards the annular sprue cross-section (64), can be introduced into the cavity (30) of the casting mould (10).

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