Method for Manufacturing a One-Piece Vehicle Wheel

Description

The present invention relates to a method for manufacturing a one-piece vehicle wheel. Furthermore, the invention relates to a vehicle wheel and an apparatus for this purpose.

STATE OF THE ART

Vehicle wheels are an important component for the safe and efficient movement of a vehicle, especially those for passenger cars and commercial vehicles. Vehicle wheels are usually manufactured using established methods based on different technologies that take into account requirements in terms of weight, strength, durability, and manufacturing costs.

One well-known method for manufacturing vehicle wheels is the forging process. In this process, an aluminum or steel blank is pressed into the desired form under high pressure. The forging process is characterized by the high strength and load-bearing capacity of the components manufactured. However, the high energy consumption and associated costs are a disadvantage. Furthermore, the so-called casting process, in particular low-pressure casting, is often used for the manufacturing of aluminum wheels. In this process, liquid aluminum is poured into a mold and then cooled in a controlled manner. The use of modern casting technologies allows complex geometries to be realized. However, casting can result in porous structures that require additional post-processing or heat treatment to improve the material properties. Finally, a process known as flow forming is often used in the manufacturing of vehicle wheels for passenger cars and/or commercial vehicles. In this process, a wheel blank is processed while being rotated and subjected to force in order to achieve the desired final form and material thickness. This process can be used in particular in the manufacturing of heavy-duty wheels.

Recent developments show the potential use of additive manufacturing processes (e.g., 3D printing) for the manufacturing of prototypes or special wheels. These processes enable the manufacturing of highly complex geometries and the customization of wheels. However, due to long manufacturing times and high costs, additive manufacturing is currently only used to a very limited extent in mass manufacturing/production.

The ETRTO (European Tire and Rim Technical Organization) standard defines technical specifications for tires and rims for passenger cars and commercial vehicles, particularly with regard to their dimensions, tolerances, valve connections, and assembly/mounting requirements. The aim of the standard is to ensure the interoperability and safety of tires and rims, regardless of their manufacturer. In particular, the ETRTO standard regulates geometric parameters such as rim width, rim height, profile contours, and mounting angles, which are decisive for the compatibility of tires and rims. The ETRTO standard has an indirect but significant impact on the manufacturing processes for passenger car and commercial vehicle wheels. On the one hand, the given specifications influence the design requirements that must be taken into account when designing rims. On the other hand, these requirements affect the choice of manufacturing methods, such as forging, casting, or rolling rims, as certain geometries and tolerances must be precisely adhered to in order to ensure compliance with the standard. Furthermore, technological advances in the manufacturing of vehicle wheels have led to the development of innovative manufacturing processes that can ensure compliance with the ETRTO standard.

Despite the existing standardization, the state of the art offers scope for innovation, particularly with regard to improving manufacturing accuracy, material utilization, and adaptation to specific application requirements, such as wheels for electric vehicles or special commercial vehicles. Such developments aim to meet standard requirements as well as achieve additional properties, such as increased energy efficiency or improved strength.

Vehicle wheels in steel construction are known to consist of a rim and a wheel disc arranged at the rim. In commercial vehicle wheels, for example, the wheel disc is pressed into the rim with a slight oversize and then permanently connected with a circumferential (partially interrupted) weld seam. The wheel disc is connected either in the rim in the transition area, the so-called ledge (cylindrical transition area between the rim shoulder and the rim well), or directly in the rim well. To achieve this, the contours of the rim and disc run parallel to each other in the axial direction from the outside of the wheel to the weld seam, which results in higher material usage and a kind of gap between the two parts. The gap between the wheel disc and the rim contour often impairs the aerodynamics of the vehicle wheel. As part of aerodynamic optimization, some vehicle manufacturers therefore use hubcaps to improve the aerodynamics of the wheel by covering its entire surface.

There are also designs with a disc and rim connection in the outer shoulder area. However, these have the distinct disadvantage that the fit of both parts can only be manufactured with great effort due to the shoulder bevels of 5° and 15°, and here too, the material overlaps lead to increased material consumption and additional weight of the wheel.

A disadvantage of the known manufacturing methods is that challenges remain in further weight reduction, cost optimization, and the integration of new material technologies, which offer scope for innovative methods.

It is an object of the present invention to at least partially overcome the disadvantages of the prior art described above. In particular, it is an object of the present invention to provide an improved method for manufacturing a vehicle wheel.

DISCLOSURE OF THE INVENTION

According to aspects of the invention, a method with the features of claim 1, a vehicle wheel with the features of claim 16, and an apparatus with the features of claim 17 is provided. Further features and details of the invention are apparent from the respective subclaims, the description, and the drawings. Of course, the features and details described in connection with the method according to the invention also apply in connection with the vehicle wheel according to the invention and the device according to the invention, and vice versa, so that mutual reference is always possible with regard to the disclosure of the invention.

According to an aspect of the invention a method for manufacturing a one-piece vehicle wheel is provided, wherein the vehicle wheel comprises a disc segment and a rim segment, and wherein the method comprises:

• • providing a one-piece preform made of metallic material, in particular a disc blank made of metallic material or a bandage made of metallic material, wherein the metallic material is specified by a material quality and/or a material thickness,
  • forming a pot from the provided one-piece preform, wherein the pot comprises the disc segment and the rim segment,
  • profiling the disc segment and/or the rim segment of the one-piece vehicle wheel with regard to a respective material thickness in different areas of the respective segments on the basis of a cold forming process, in particular on the basis of a flow forming process.

This has the advantage that the producibility of the one-piece vehicle wheel is significantly simplified and improved by using a one-piece preform made of metallic material, which is then formed into a disc segment and a rim segment of the one-piece vehicle wheel. By profiling the respective segments, a variable material thickness can be achieved in order to meet the desired and/or required requirements, for example, of the ETRTO standard. Furthermore, this ensures the stability and strength of the vehicle wheel for safe operation.

A further advantage can be achieved within the scope of the invention if the diameter of the rim segment corresponds to a predetermined diameter of a rim well of the vehicle wheel after forming the pot, and wherein the method further comprises:

• • Forming a transition area of the vehicle wheel by means of a forming medium in a tool for manufacturing the vehicle wheel,
  • wherein the forming medium is pressed against a negative mold of the tool dependent on a controlled generated pressure in such a way that the transition area is formed on the basis of a given specification of a contour of the vehicle wheel,
  • wherein the transition area is specified as an area of the vehicle wheel which is arranged between a wheel mounting face of the disc segment and an outer rim shoulder of the rim segment in order to form a one-piece continuous contour of the vehicle wheel.

This allows the one-piece vehicle wheel comprising a continuous contour in the transition area of the vehicle wheel, which meets both the aerodynamic and functional requirements of the wheel, as required for passenger cars or commercial vehicles. Further, this ensures a high degree of flexibility in the forming of one-piece vehicle wheels, as the forming process can be adapted more cost-effectively and quickly. Furthermore, the forming of the transition area is significantly improved by means of the forming medium being used, as the contour of the vehicle wheel can be manufactured more precisely and quickly in the transition area. This also has the advantage that the transition area can be optimized by means of a special surface design of the contour in such a way that the aerodynamics are improved. In addition, the flexibility and adaptability of the forming medium make it possible to manufacture difficult and irregular geometries that would be difficult or impossible to achieve with rigid tools.

Within the scope of this invention, a forming medium should be understood to be a medium that is used in a forming process to interact with the workpiece, such as a preform made of metallic material or a cylindrical pot made of metallic material, by means of pressure or other physical influences, and to bring it into a specific form, such as a vehicle wheel. In the manufacturing of the vehicle wheel, in particular the disc and/or rim segment, a forming medium can be used to form the material and ensure consistent force distribution.

On the one hand, a typical forming medium can be oil, water, or a mixture of oil and water. These forming media can be used, for example, in a process known as Internal High-Pressure Forming (IHF, German: IHU). In IHF processes, also known as Hydroforming, a liquid medium such as oil or water is pressed into a preformed workpiece under very high pressure. This presses the material against the mold wall (die) and causes it to take on the contours of the mold.

On the other hand, an elastic medium such as an elastomer or a comparable elastic plastic can be used. This elastic medium acts on the material of the vehicle wheel to be manufactured according to the same principle as the liquid forming medium and deforms it by means of controlled pressure.

This principle corresponds to the so called Guerin method, which uses a flexible rubber cushion as the forming medium, pressing the material evenly against a rigid mold during pressing. The rubber cushion acts as an adaptable medium that fits to the workpiece and thus exerts consistent pressure on the material. For this reason, these technologies have rarely been used in rim manufacturing to date, as the strength requirements and precision are considered to be higher in this field. According to many years of expert opinion, such forming media in liquid or elastic form (as in the IHF or Guerin method) have therefore not been used in rim manufacturing, as rims must meet high structural requirements. Surprisingly, tests with the forming media used in this invention have shown that they can be advantageously applied in the inventive manufacturing method in terms of precision, safety, efficiency, and cost-effectiveness.

It is optionally conceivable that the preform made of metallic material comprises a seamless tube made of metallic material. The tube can then be cut to size to fit the vehicle wheel to be manufactured and then represents the preform, so to speak.

Then, during the manufacturing of the vehicle wheel, the outer diameter, the wall thickness, and the length of the tube can be selected in such a way that they meet the basic requirements of the finished vehicle wheel. In this step, the cross-section of the tube can still be adjusted, for example, by creating the desired contour for the rim and disc segment of the vehicle wheel. For example, the tube can be further formed by rotational forming or rolling. Depending on the vehicle wheel design, complex patterns can be created, e.g., by laser cutting, especially in lightweight construction applications. Based on an Internal High-pressure Forming process (IHF), the tube can be inserted into a die and the material is pressed against the die wall using a liquid forming medium to form the rim and disc segment of the vehicle wheel. This process is particularly suitable for the manufacture of one-piece, seamless vehicle wheels. Alternatively, the disc segment can be manufactured by flow-forming, for example, whereby material can be drawn out of the tube and distributed equally. This enables precise control of the material thickness and higher material strength through cold hardening. Further advantages of this method are that the finished vehicle wheel does not comprise any weld seams or joints, which increases the structural integrity and strength of the vehicle wheel, and that different tube preforms are widely applicable and can be adapted for different designs and applications.

It is also conceivable that part of the inventive method is based on hot forming, which can be used in combination with other forming methods. It is also possible that this type of forming takes place above a respective recrystallization temperature of a respective metal used. The hot forming is advantageously suitable for components that have to withstand high loads, such as vehicle wheels. Hot forming methods can include forging, hot rolling, or form hardening.

The recrystallization temperature can be defined as the temperature at which, for example, a metal recrystallizes completely within a certain observation period. As a rule of thumb, it is often estimated at 40% or 50% of the absolute melting temperature of the respective metal. Recrystallization is a term used in metallurgy and crystallography to describe the reduction of lattice defects in crystallites through structural changes resulting from nucleation and grain growth. It is accompanied by a decrease in strength and usually grain refinement. The prerequisite for this are dislocations being introduced by the forming, which act as nuclei for the formation of new crystallites. If the forming takes place above the recrystallization temperature, dynamic recrystallization of the respective metal can be observed.

Optionally, it is possible that prior to the forming of the transition area the method further comprises:

• • Inserting the pot into the tool for further forming the respective segments of the vehicle wheel, wherein the tool is divided horizontally or vertically, and wherein the respective divided tool is provided as a negative mold for forming the transition area.

This allows for easier handling of the pot due to its, for example, cylindrical or rotationally symmetrical geometry, as in the case of vehicle wheels, since they can fix the blank in its natural horizontal orientation. The division allows precise alignment and forming of the vehicle wheel. Furthermore, horizontal divisions of tools have the advantage of enabling a more compact machine design, which saves space in manufacturing.

The vertical division facilitates the exact centering of the workpiece, which is particularly important for rotationally symmetrical components such as rims in order to avoid imbalances.

Furthermore, vertically divided tools can be more easily integrated into multi-stage manufacturing lines, as they can be accessed from both sides. Large and heavy workpieces can be handled more easily, as they are supported by gravity in the vertical position.

A further advantage can be achieved within the scope of the invention if, during the forming of the transition area in the vertically divided tool, the forming medium is pushed in a horizontal direction on both sides in response to the controlled generated pressure so that the transition area of the pot is pressed against the negative mold of the vertically divided tool, and the method further comprises at least one of the following steps:

• • guiding the forming medium to support the forming of the transition area,
  • stabilizing an open end of the rim segment to prevent buckling or bulging of the rim segment.

In this way, the method for manufacturing a one-piece vehicle wheel can enable precise control of the forming of the transition area to ensure that this area is pressed against the negative mold of the vertically divided tool by expanding the forming medium. By guiding the forming medium and stabilizing the open end of the rim segment, precise control of the forming of the transition area can be achieved to prevent buckling or bulging of the rim segment of the pot.

“Guiding the forming medium” means a controlled, directional supply or movement of a component or material in response to a defined process parameter, wherein the supply is continuously or step-wise adjusted by one or more feedback mechanisms. The control may be realized by hydraulic, pneumatic, mechanical, electromagnetic, thermal, or software-based means, alone or in combination. “Guiding” does not require that the component is physically attached to a transport mechanism; it also covers the purposeful shaping of a flow field, pressure gradient, or field-induced motion that causes the component to follow a predetermined path.

Any embodiment of the inventive method that (i) supplies the forming medium to the transition area, (ii) imparts a directed influence (pressure, flow, thermal, acoustic, or electromagnetic), and (iii) employs at least one feedback element to adapt the influence in real time, falls within the meaning of “guiding of the forming medium” for the purposes of the claims.

According to a further possibility, the method during the forming of the transition area in the horizontally divided tool may further comprise:

• • filling the pot with the forming medium,
  • closing the pot at the open end of the rim segment by means of a closing device,
  • applying the controlled generated pressure to the forming medium by means of a pressure device in order to press the forming medium against the transition area and force the transition area into the negative mold of the horizontally divided tool,
  • guiding a position of the closing device in dependence on the spread of the forming medium due to the controlled generated pressure exerted on the forming medium.

In this way, the method for manufacturing a one-piece vehicle wheel can enable precise control of the forming of the transition area to ensure that this transition area is pressed against the negative mold of the horizontally divided tool. By guiding the position of the closing device, precise control of the forming of the transition area can be achieved. The forming of vehicle wheels using liquid or elastic forming media makes it possible to ensure uniform pressure distribution of the forming medium on the transition area and/or gentle treatment of the material of the transition area.

Further, the guiding of the position of the closing device, in particular a closing cylinder, allows the closing device for following from the edge of the pot, i.e., the position of the closing device is guided in order to build up or maintain the pressure of the forming medium.

The guiding of the position of the closing device means a controlled positioning, moving, or actuation of the sealing or closing device in a manner that is dynamically linked to the spatial propagation of the forming medium, where the propagation is itself generated by a deliberately applied, controllable pressure on the medium. This guiding can be performed, for example, by pressure, heat, or electromagnetism. Any method according to the invention that (i) detects the spatial advance of the forming medium, (ii) applies a controlled pressure to the forming medium, and (iii) moves the closing device in a manner that is functionally dependent on the detected advance is covered by the term guiding of the closing device. The dependence may be linear, non-linear, stepwise, or event-driven, and the actuation may be continuous or discrete.

It may be further advantageous for the forming medium to be of a liquid form and/or an elastic form, wherein preferably the liquid form comprises water, and/or preferably the elastic form comprises an elastic plastic, in particular an elastomer.

This allows the pressure to be distributed equally over the entire surface of the workpiece, regardless of the tool geometry, in the case of liquid forms, i.e., liquids such as oil or water. This reduces the risk of local deformations, cracks, or material failure of the vehicle wheel to be manufactured. This enables, for example, internal high-pressure forming (IHF) for forming the vehicle wheel, which allows precise forming. Furthermore, in liquid-based forming processes such as internal high-pressure forming, the material is pressed against an existing mold wall as a negative mold, so that less complex tools are required.

In the case of an elastic mold, such as an elastomer, it adapts flexibly to complex geometries and presses the material equally against the mold. This advantageously minimizes stress in the material of the vehicle wheel. Furthermore, the die (molding tool) only needs to be manufactured on one side, as the elastic medium exerts pressure from the other side. This advantageously reduces tooling costs considerably. The forming of vehicle wheels using liquid or elastic forming medium therefore offers advantages such as consistent pressure distribution, material protection, the possibility of manufacturing complex geometries, and reduced tooling costs.

It is also conceivable that a diameter in an area of a transition from the disc segment and the rim segment substantially corresponds to a predetermined final diameter of the disc segment, and wherein the method further comprises:

• • forming a transition area based on a flow forming process, wherein the transition area is arranged between a wheel mounting face of the disc segment and the outer rim shoulder, preferably the outer rim flange, of the rim segment in order to form a one-piece continuous contour of the vehicle wheel.

This has the advantage that the transition area can be flexibly adapted in terms of material thickness and design. Furthermore, this enables the one-piece vehicle wheel to have a continuous contour in the transition area of the vehicle wheel, which meets both the aerodynamic and functional requirements of the wheel, as required for passenger cars or commercial vehicles.

For example, the method may further comprise:

• • inserting the pot into a tool comprising a first die and a second die,
  • reducing a diameter of the rim segment by means of the second die.
    This makes it possible to provide a desired form of the rim segment to be manufactured in order to meet the specified requirements of the standard. Furthermore, rim diameters can advantageously be provided as required, for example, for Passenger cars or commercial vehicles.

A die for rim manufacturing is typically understood to be a solid, precisely manufactured tool made of high-strength steel. It has a hollow cylindrical form whose inner contour corresponds exactly to the desired outer form of the rim. The surface of the die is smooth and polished to ensure a high-quality surface finish of the manufactured rim.

It is also advantageous if the profiling of the disc segment and/or the rim segment is performed based on a combination of an external high-pressure forming and flow forming process. In the external high-pressure forming (EHF; German: AHU), the disc and/or rim segment is formed or reshaped to form a continuous contour of the vehicle wheel. EHF is already used in the automotive industry for body parts where precise outer contours are required to meet aerodynamic or aesthetic requirements. However, it can be used alone or in combination with other methods effectively in the manufacturing of a one-piece vehicle wheel for the precise forming of individual areas of the wheel disc and/or rim segment.

It is also conceivable that the method further comprises:

• • applying a flow forming process to the preform, in particular to a bandage made of metallic material, in order to reduce a thickness of the material of the preform in sections and, as a result, increase a width of the preform, in particular the steel bandage, thereby reinforcing specific sections of the rim segment, preferably an inner and/or outer rim flange,
  • profiling the formed material of the rim segment using a flow forming process to form the required material quality and the final form of the profile of the rim segment.

The flow forming allows the preform made of metallic material, for example a steel bandage, to be formed into the desired form or dimension by mechanical forces. This has a beneficial effect on the material properties and geometry of the pre-form.

In addition, it may be advantageous within the scope of the invention for the method to further comprise at least one of the following steps:

• • cutting out at least one opening in the area of the disc segment using a punching process, a laser cutting, plasma, or water jet cutting process,
  • cutting out at least three openings in the area of the disc segment using a punching process, a laser cutting, plasma, or water jet cutting process, wherein each opening has an identical form and/or wherein the at least three openings are arranged at equal distances from each other in the area of the disc segment.

This allows, for example, for mechanically cutting openings out of the material during punching, e.g., using a punch and a die. This has the advantage that the disc segments of the vehicle wheel processed in this way comprise clean and precise cut edges. Furthermore, this method step can be easily integrated with other forming processes in a production line. During, for example, a forming of the disc segment, e.g., during deep drawing or flow forming, openings can be manufactured using previously inserted embossing or punching tools, which reduces the number of separate manufacturing steps. Precise openings can be created just as quickly and efficiently using laser cutting, plasma cutting, or water jet cutting methods. This is particularly advantageous in manufacturing complex or filigree designs for vehicle wheels. Furthermore, this method has the advantage of minimizing stress on the material of the vehicle wheel and preventing cracks or deformations.

Furthermore, it is conceivable that the method further comprises:

• • profiling the disc segment, in particular the transition area and the wheel mounting face, in such a way that an outside, closed contour line is provided in order to achieve an aerodynamic effect of the vehicle wheel.

This allows the contour line of the disc segment of the vehicle wheel to ensure the advantageous aerodynamic properties of a corresponding separate wheel cover. Furthermore, the contour line of the vehicle wheel from the wheel mounting face to the outer rim flange facilitates material savings regarding the vehicle wheel, which has a favorable effect on the CO2-footprint of the product.

It is possible within the scope of the invention that the method further comprises:

• • profiling the disc segment, in particular the transition area, in such a way that a transition element of the transition area has an orientation relative to a central axis of the vehicle wheel which is directed axially from the outside to the inside, axially from the inside to the outside, or substantially perpendicular to the central axis of the vehicle wheel.

This has the advantage that a vehicle wheel can be flexibly applied to different vehicle wheel types with a suitable offset (ET value) based on the manufacturing principle. The offset is understood as the axial distance between the inner contact surface of the wheel and the center of the rim contour. Furthermore, this allows the required vehicle wheel to be provided for different vehicles, such as passenger cars, commercial vehicles, a truck, or a trailer, with a corresponding alignment of the transition element of the disc segment.

It is also conceivable that the method further comprises:

• • Calibrating a diameter of the rim segment depending on the material quality.

This allows for guaranteeing uniform and precise compliance with the intended diameters. Furthermore, this minimizes deviations and ensures an optimal fit of the vehicle wheel. Furthermore, this allows the calibration process to smooth out small surface irregularities in the area of the rim segment that may arise during the manufacturing process.

It is further possible that, after forming the pot, the diameter of the rim segment corresponds to a predetermined diameter of a rim well of the vehicle wheel, and the profiling further comprises:

• • Forming a transition area between the disc segment and the rim segment of the vehicle wheel by means of rotating profile rollers,
  • wherein, after the forming of the transition area, the disc segment comprises a circular geometry.

This has the advantage that the one-piece vehicle wheel comprises a continuous contour line in the transition area of the vehicle wheel, which meets both the aerodynamic and functional requirements of the wheel, as required for passenger cars or commercial vehicles. Furthermore, the forming of the transition area by means of the profile rollers is further improved, as the contour of the vehicle wheel in the transition area can be manufactured more precisely and quickly. This also has the advantage that the transition area can be optimized by a special surface design of the contour in such a way that the aerodynamics are improved.

It is possible that the profiling of the rim segment further comprises at least one of the following steps:

• • performing a further profiling step using the rotating profile rollers to provide a conical end on an open end of the pot,
  • performing several further profiling steps using the rotating profiling rollers in such a way that a material of the rim segment only flows from the open end of the pot in direction of the transition area during the several profiling steps in order to reshape the specified rim contour.

This allows for providing a desired shape and material quality of the rim segment to be manufactured in order to meet the specified requirements of the standard. Furthermore, rim diameters can be advantageously provided as required, for example, for Passenger cars or Commercial vehicles. Furthermore, the desired rim contour can be advantageously divided into one or more profile forming processes in such a way that a consistent forming takes place during the method according to the invention, which allows the rim material to flow only from the open pot end. Thus, when carrying out a multi-stage profiling process, the transition area between the disc segment and the rim segment can be formed in the first profiling step, and in the following profiling steps, the disc segment can be so to speak decoupled during the subsequent further profiling steps for forming the rim segment.

The invention also relates to a vehicle wheel for a vehicle, in particular for a passenger car or a commercial vehicle, which is manufactured according to the method of the invention. The vehicle wheel according to the invention thus offers the same advantages as those described in detail with reference to the method of the invention.

The invention also relates to an apparatus for manufacturing a vehicle wheel, wherein the apparatus comprises means adapted to carry out the method according to the invention. The apparatus according to the invention thus offers the same advantages as those described in detail with reference to the method according to the invention.

Further advantages, features, and details of the invention are apparent from the following description, in which embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. Showing:

FIG. 1 a schematic visualization of a method according to embodiments of the invention,

FIG. 2 a schematic representation of a process according to embodiments of the invention,

FIG. 3 is another schematic representation of a sub-process according to embodiments of the invention,

FIG. 4 is another schematic representation of a sub-process according to embodiments of the invention,

FIG. 5 a further schematic representation of a sub-process according to embodiments of the invention, and

FIG. 6 a schematic representation of a vehicle wheel according to embodiments of the invention.

In the following figures, identical reference numerals are used for the same technical features, even if they belong to different embodiments.

FIG. 1 shows a schematic visualization of a method according to embodiments of the invention. In particular, FIG. 1 shows a method 100 for manufacturing a one-piece vehicle wheel 1, wherein the vehicle wheel 1 comprises a disc segment 2 and a rim segment 3. The method 100 comprises, in a step 101, providing a one-piece preform 4 made of metallic material, in particular a disc blank 4 made of metallic material or a bandage 4 made of metallic material, wherein the metallic material is specified by a material quality and/or a material thickness. In step 102, a pot 5 is formed from the provided one-piece preform 4, wherein the pot 5 comprises the disc segment 2 and the rim segment 3. In step 103, the disc segment 2 and/or the rim segment 3 of the one-piece vehicle wheel 1 are profiled with regard to a respective material thickness in different areas of the respective segments 2, 3 on the basis of a cold forming process, in particular on the basis of a flow forming process.

Furthermore, FIG. 1 shows an apparatus 70 for manufacturing a one-piece vehicle wheel 1, comprising means, in particular tools 50, 60, which are designed to carry out the method 100 according to the invention.

FIG. 2 shows a schematic representation of a process according to embodiments of the invention. In particular, FIG. 2 shows an exemplary process flow for manufacturing a one-piece vehicle wheel. The manufacture of the one-piece vehicle wheel 1 involves a multi-stage process comprising various techniques and methods to achieve the final form and structure of the vehicle wheel 1. An exemplary process flow is described in detail below:

The step 201 may, for example, consist of unwinding a metal strip or rim blank from a metal roll provided. The metal may be, for example, a high-quality steel alloy of any type or aluminum. After unwinding in step 201, the rim blank may be further processed or adjusted in accordance with the further steps 202, 203, wherein the adjustment may comprise straightening the rim blank, for example, straightening the surface and deburring the edges of the metal strip. Subsequently, in step 204, the metal strip that has been processed in this way is then cut to the required length, corresponding to the size of the rim to be manufactured. In step 205, the cut material, i.e., the cut rim blank, in particular the steel rim blank, is bent into a circular or cylindrical shape, which forms the one-piece preform for the vehicle to be manufactured. In step 206, the ends of the steel rim blank bent in this way can be welded together at the blunt ends to form a closed ring. After welding, in step 207, the surface of the rim is smoothed, for example, to remove irregularities, such as those at the weld seam. The circularly bent steel rim blank is inserted between the flow forming tools in step 208 for the flow forming process. Special tools (e.g., pressure rollers) are used for the flow forming process, which are configured so that they can reduce the thickness of the steel rim blank locally in a targeted manner. The material displaced by the pressure rollers causes the rim blank to grow in width in the axial direction. In step 209, the flow forming process is used to further form the material of the rim under pressure in sections in order to increase its strength and reduce its weight. Furthermore, in this step, a desired diameter of the rim 2 is provided in such a way that it corresponds to the diameter of a specified rim well of the vehicle wheel 1. This creates a shape, in particular a so-called pot 5, which has an open end.

The next processing step 210 comprises a profiling and calibration process in which the rim profile of rim 2 is formed step by step in sections or locally in several, for example up to three, processing steps in order to achieve the final contour (line). During processing step 210, which may comprise several profiling steps, the profiling may further comprise forming 210a a transition area 40 between the disc 2/disc segment 2 and the rim 3/rim segment 3 of the vehicle wheel 1 by means of rotating profile rollers, wherein after forming the transition area 40, the disc segment 2 has a circular geometry. For example, the profiling of the rim segment 3 in step 210 may further comprise at least one of the following steps 210b, c:

• • performing 210b a further profiling step using the rotating profile rollers to provide a conical end at an open end of the pot,
  • performing 210c a plurality of further profiling steps using the rotating profiling rollers, such that a material of the rim segment only flows from the open end of the pot in direction toward the transition area during the plurality of profiling steps in order to reform the predetermined rim contour line.

The transition area 40 comprises, for example, a transition element 11, an outer rim flange 12, and an outer rim shoulder 14 of the vehicle wheel 1. In other words, the respective elements 11, 12, 14 of the transition area 40 are formed by the aforementioned profiling steps of processing step 210.

Then, in step 211, the hole in the rim segment 3 for the valve can be punched. Finally, the dimensions of the finished rim segment 3 can be checked (not shown).

FIG. 3 shows a schematic representation of a sub-process according to embodiments of the invention. In particular, FIG. 3 shows a part of the manufacturing process of the vehicle wheel 1, which shows the forming of the pot 5 by means of a forming medium 6 in a vertically divided tool 50. The left half of FIG. 4 shows the time phase before forming, and the right half of FIG. 4 shows the time phase after forming the transition area 40 of the vehicle wheel 1.

The pot 5 can be inserted into the tool 50 for further forming of the respective segments 2, 3 of the vehicle wheel 1 or the pot 5 and is adjacent to a die 53 at the top. The die 53 forms a negative mold for the desired vehicle wheel 1. The transition area 40 can be specified as an area of the vehicle wheel which is arranged between a wheel mounting face of the disc segment 2 and an outer rim shoulder of the rim segment 3, preferably an outer rim flange 12, in order to form a one-piece continuous contour of the vehicle wheel 1. This means, for example, that the die of the split tool 50 is provided as a negative mold for forming the transition area 40.

The diameter of the rim segment 3 of the pot 5 as shown in FIG. 3 can correspond to a predetermined diameter of a rim well 16 of the vehicle wheel 1 (see also FIG. 6). When forming the transition area 40, the forming medium 6 in the tool 50 is pressed against the negative mold 53 of the tool depending on a controlled generated pressure in such a way that the transition area 40 is formed on the basis of a given specification of a contour of the vehicle wheel 1 in order to form a one-piece continuous contour line of the vehicle wheel 1.

Furthermore, when forming the transition area 40 in the vertically divided tool 50, the forming medium 6 can be pressed in both directions horizontally depending on the controlled generated pressure, so that the transition area 40 of the pot 5 is pressed against the negative mold of the die 53. Optionally, a guiding of the forming medium 6 may be performed to support the forming of the transition area 40. Furthermore, for example, the open end of the rim segment 3 or pot 5 may also be stabilized in order to prevent buckling or bulging of the rim segment 3 of the pot 5.

FIG. 4 shows a further schematic representation of a sub-process according to embodiments of the invention. In particular, FIG. 4 shows a part of the manufacturing process of the vehicle wheel 1, which depicts the forming of the pot 5 by means of a forming medium 6 in a horizontally divided tool 50. The upper half of FIG. 4 shows the time phase before the forming, and the lower half of FIG. 4 shows the time phase after the forming of the transition area 40 of the vehicle wheel 1.

The pot 5 inserted into the horizontally divided tool 60 can be filled with a forming medium 6, such as a liquid mold 6 or a liquid medium 6, for forming. The liquid forming medium 6 can be, for example, a liquid such as water or oil. The pot 5 can then be closed at its open end (rim segment 3) by means of a closing device 63, such as a closing cylinder 63. By exerting a controlled generated pressure on the forming medium 6 by means of a pressure apparatus on the closing device 63, the liquid 6 as the forming medium can press against the transition area 40 and thus press this transition area 40 into the negative mold of the upper and lower tools 61, 62 in order to form the transition area 40, as shown, for example, in the lower half of FIG. 4. Guiding the position of the closing device 63 dependent on the expansion of the forming medium 6 due to the controlled generated pressure exerted on the forming medium 6 enables the precise forming process of the transition area 40.

FIG. 5 shows another schematic representation of a sub-process according to embodiments of the invention. In particular, FIG. 5 shows a part of the manufacturing process of the vehicle wheel 1, which depicts the tapering of the rim segment 3 of the pot 5 in a horizontally divided tool 50. The left half of FIG. 5 shows, by way of example, the time phase before the diameter of the rim segment 3 is reduced or tapered. The right half of FIG. 5 shows the time phase after the transition area 40 of the vehicle wheel 1 has been tapered.

When processing the pot 5, it may be possible, for example, that a diameter in the area of a transition from the disc segment 2 and the rim segment 3 substantially corresponds to a predetermined final diameter of the disc segment 2, as shown in the left half of FIG. 5.

The transition area 40 can be formed, for example, on the basis of a flow forming process, whereby the transition area 40 is arranged between a wheel mounting face 10 of the disc segment 2 and the outer rim shoulder 14 of the rim segment 3, preferably the outer rim flange 12, in order to form a one-piece continuous contour of the vehicle wheel.

For example, the pot 5 can first be inserted into a die 54 of the vertically divided tool 50. Then, optionally, the rim segment 3 (and/or the disc segment 2) can be formed by means of a respective die 54 used or, alternatively, another tool 54 so that the diameter of the rim segment 3 is reduced or tapered.

FIG. 6 shows a schematic sketch of a profile of a vehicle wheel according to embodiments of the invention. FIG. 6 in particular shows a schematic cross-section of a vehicle wheel according to the invention, for example for a passenger car, for a commercial vehicle such as a city delivery van or box van, or for a trailer. The vehicle wheel 1 comprises a disc segment 2 and a rim segment 3. A transition area 40 is arranged between a wheel mounting face 10 of the disc segment 2 and an outer rim shoulder 14 of the rim segment 3, preferably an outer rim flange 12 of the rim segment 3. As shown in FIG. 6, the transition area 40 comprises the transition element 11, the outer rim flange 12, and the outer rim shoulder 14.

The disc segment 2 comprises a wheel mounting face 10 for connecting the wheel 1 to a vehicle hub (hub not shown) and a transition element 11, wherein the transition element is arranged between the wheel mounting face 10 and the outer rim flange 12. A transition area 40 comprises an area between the wheel mounting face 10 and the outer rim shoulder 14, i.e., this area 40 comprises, for example, a transition element 11 as well as an outer rim flange 12 and the outer rim shoulder 14. The transition element 11 of the disc segment 2 is arranged directly on the outer rim flange 12 of the rim segment 3 or is one-piece connected thereto. The transition element 11 according to FIG. 6 is shown with an orientation relative to a central axis of the vehicle wheel 1 that is directed axially from the outside to the inside. The wheel profile shown in FIG. 6 may be suitable for a passenger car, for example. Alternatively, other orientations for the transition element 11 relative to the central axis of the vehicle wheel, such as axially from the inside to the outside or essentially perpendicular to the central axis of the vehicle wheel 1, may also be provided. The transition element 11 and the outer rim flange 12 are designed as a circumferential, free-of welding-seams material section of the vehicle wheel 1.

The rim segment 3 may be provided, for example, as a drop center rim 3, which may be designed, for example, as a 5° or 15° steep shoulder rim. The rim segment 3 may also be symmetrical. The profile of the rim segment 3 may comprise different sections. According to the embodiment shown in FIG. 6, the rim segment 3 comprises an outer and an inner rim flange 12, 13 as well as an outer rim shoulder 14 and an inner rim shoulder 15. A drop center rim well 16 is formed between the two rim shoulders 14, 15, which may comprise a drop center base. Optionally, it is possible that so-called humps can be arranged between the rim shoulders 14, 15 and the drop center rim 16.

Furthermore, the transition element 11 may comprise a recess for a valve passage for a valve or ventilation holes.

The above description of the embodiments describes the present invention exclusively in the context of examples. Of course, individual features of the embodiments can be freely combined with each other, provided that this is technically sensible, without departing from the scope of the present invention.

LIST OF REFERENCE SIGNS

• • 1 Vehicle wheel
  • 2 Disc segment, disc
  • 3 Rim segment, rim
  • 4 Preform, disc blank, bandage
  • 5 Pot
  • 6 Forming medium
  • 10 Wheel mounting face
  • 11 Transition element
  • 12 Outer rim flange
  • 13 Inner rim flange
  • 14 Outer rim shoulder
  • 15 Inner rim shoulder
  • 16 (Deep) rim well, drop center rim
  • 40 Transition area
  • 50 Tool, vertically divided
  • 51 Lower part of the tool
  • 52 Support ring
  • 53 Die
  • 54 Additional die, additional tool
  • 60 Tool, divided horizontally
  • 61 Upper tool
  • 62 Lower tool
  • 63 Closing device, closing cylinder
  • 70 Apparatus for manufacturing
  • 100 Method
  • 101 Providing Step
  • 102 Forming Step
  • 103 Profiling step