INTERNALLY VENTILATED ROTOR

Description

[0001] The invention relates to an internally ventilated rotor and the joining cores that can be used to manufacture it, as well as to a use of the internally ventilated rotor.

[0002] It is known that the service life of disc brake components can be significantly increased by improving cooling performance and thus achieving a lower operating temperature of the disc brake. Accordingly, numerous proposals for improving the cooling performance of disc brakes have been made in the prior art.

[0003] The German patent application DE 1O 2017 206 249 A1 describes a liquid-cooled brake disc for a disc brake. It is made of metal using 3D printing and has no internal ventilation.

[0004] High-strength, fiber-reinforced brake discs are often internally ventilated. They feature one or more cooling channels. Cooling occurs by transferring heat to the air flowing through the channels.

[0005] Various internally ventilated rotors for disc brakes have been proposed in the prior art. For example, DE 601 16 780 T2 relates to a method for manufacturing a brake ring that has ventilation channels and is made of a ceramic material such as C / SiC. The ventilation channels are formed using a core made of a metallic material, which is melted out.

[0006] Publication EP 3093517 A2 relates to a carbon-ceramic brake disc comprising a carrier body with cooling channels in the central section and friction layers. The carrier body consists of a plurality of layers having components more similar to those of the friction layers. The carrier body may consist of two or more layers. GB 2444927 A relates to a ventilated brake disc formed from a plurality of porous bodies. The porous bodies are arranged such that each wing formation is in contact with at least one other porous body to define a ventilation space within the formed brake disc. The porous bodies are connected to one another by means of a ceramic or other material arranged within the pores of the porous bodies.

[0007] Patent DE 101 64 627 C1 proposes that, during the manufacturing process, an electric current is passed through the pressable mass or the green body, as well as through at least one mold core, for heating purposes.

[0008] In the patent application DE 198 34 571 A1, it is proposed to add a metal- or silicon-containing core, which is used as a metal or silicon source during melt infiltration.

[0009] Patent DE 102 34 400 B3 relates to a process for manufacturing hollow bodies from fiber-reinforced ceramic materials, using compressible cores. During compression with a compressible binder and a fiber-containing compound, the cores are compressed by at least 5% in the compression direction. The cores consist of a material that undergoes subsequent carbonization in a non-oxidizing atmosphere at a temperature of approximately 750 °C to approximately 1100 °C, or is at least partially pyrolyzed with volume shrinkage. The patent describes the use of multilayer cores made of foamed polymers in sandwich-like structures.

[0010] The internally ventilated rotors available according to the publications cited above possess outstanding properties. However, there is still potential for improvement, particularly regarding their cooling performance. Due to the manufacturing process, the connecting areas between the cooling channels, which join the friction discs, are solid. They have the same composition as the friction discs, as the same difficult-to-mold material is used to produce both the friction discs and the connecting areas. During the manufacturing process, this material is filled into the recesses in the core where the connecting areas are formed. The recesses must be very wide to allow the material to fill the area effectively despite its difficult formability. Furthermore, any pyrolysis residues from the cores must be removed, which can lead to a less than ideal surface finish.

[0011] The present invention is based on the objective of providing an internally ventilated rotor for a disc brake that increases the service life of the braking system, in particular the brake disc and the brake pads, and is also easy to manufacture.

[0012] This problem is solved by an internally ventilated rotor with the features of claim 1, a joining core with the features of claim 11, and a use of the internally ventilated rotor according to claim 13. According to the invention, the internally ventilated rotor comprises two interconnected disk elements and a joining core with an internally ventilated cooling zone and a cooling element between the disk elements, wherein the cooling element connects the disk elements so that heat is transferred directly from the cooling element to the air located in the cooling zone, and wherein the disk elements and the cooling element contain fibers, the cooling element having a lower average volume fraction of fibers than the disk elements, and the cooling zone being open radially inwards and outwards so that air can flow through the cooling zone, characterized in that the joining core has a structure obtained by additive manufacturing.

[0013] In embodiments not according to the invention, the internally ventilated rotor comprises only one disk element arranged between cooling elements. At least one cooling element is arranged on each of the two surfaces of the disk element, with one cooling zone located on one side of the disk element and a second cooling zone located on the other side of the disk element.

[0014] Preferably, the internally ventilated rotor according to the invention is a silicon carbide ceramic internally ventilated rotor. In the context of the present invention, silicon carbide ceramic means that the rotor contains 10–90 wt.% SiC. It may also contain, for example, 5–40 wt.% free silicon. The mass fractions of Si and SiC can be determined according to DIN EN ISO 21068-2.

[0015] The disc element volume can be, for example, 5-95% of the total rotor volume. The cooling element volume can also be, for example, 5-95% of the total rotor volume. The disc element volume includes the volume of all disc elements of the rotor, whereby any friction linings present are considered part of the disc element. The cooling element volume includes the volume of all cooling elements of the rotor, excluding the cavities used for internal ventilation. The total rotor volume is considered to be the sum of the cooling element volume and the disc element volume.

[0016] According to the invention, the cooling element has a lower average volume fraction of fibers than the disc elements. This means that the cooling element has a lower average volume fraction of fibers than the first disc element and also a lower average volume fraction of fibers than the second disc element.

[0017] This means the rotor components are optimized for their specific mechanical loads during braking. Firstly, the caliper and pads compress the disc, generating (only) compressive stresses. Secondly, the caliper (due to multiple distributed pistons) exerts uneven axial pressure at several points on the disc, which is rigidly connected to the axle. This causes the disc to bend. The highest stresses occur on the outer surfaces of the disc (highest deformation), with one outer surface experiencing compression and the other tensile stress. In the interior (where the cooling zone is located), the deformations are less, and therefore the stresses are also lower. The proposed rotor takes these varying stresses into account. The fiber content is lower where the stresses are lower and higher where the stresses are higher. The elongation at break is thus adapted to the stresses.Deformations adapted to those that occur in the different areas of the rotor during braking in practice.

[0018] A lower fiber content in the cooling element results in good and essentially direction-independent thermal conductivity. In the disk elements, the thermal conductivity is lower overall due to their higher fiber content. Nevertheless, heat dissipates very well from the rotor. In the axial direction, the disk element, which has lower thermal conductivity, has a very large cross-section available for axial heat conduction. After transitioning to the cooling element, the cross-section does become smaller, as the cooling zone occupies part of the cross-section. However, the cooling element, with its higher thermal conductivity and lower fiber content, is then available for axial heat flow. Overall, the fiber content in the rotor according to the invention is therefore optimized not only for mechanical stress but also for thermal stress.

[0019] Preferably, the cooling element has a higher average mass fraction of SiC than the disk elements. The respective mass fraction of SiC can be determined according to DIN EN ISO 21068-2.

[0020] The invention is not limited with respect to the connection(s) existing between the disc elements, provided that the connection(s) withstand the forces acting on the rotor during braking. The cooling element is arranged on at least one disc element, preferably on both disc elements. It is located between the disc elements.

[0021] Preferably, the cooling element connects the disc elements. This simultaneously improves heat dissipation and increases the mechanical stability of the rotor. A larger cooling surface is available when one or more cooling elements bridge the internally ventilated cooling zone. The direct transfer of heat from the cooling element to the air in the cooling zone is then particularly efficient. The mechanical stability of the rotor is also increased, as connecting cooling elements absorb at least some of the forces transmitted to the rotor by the brake pads during braking. Ultimately, a rotor in which one or more cooling elements connect the disc elements can be designed smaller, since the same heat dissipation and mechanical stability can then be achieved with thinner disc element walls. This allows for even lighter, high-performance braking systems.

[0022] The advantages described in the preceding paragraph are particularly pronounced when, in the section of the rotor where the brake pads bear, the connection(s) between the brake discs are closely spaced. This section of the rotor can be defined for any rotor using a hollow cylinder whose axis coincides with the rotor's axis of rotation. The distance of the inner surface of the cylinder corresponds to the smallest distance the brake pad is from the axis of rotation. The distance of the outer surface of the cylinder corresponds to the largest distance the brake pad is from the axis of rotation.

[0023] There are no restrictions regarding the path of the cooling element from one disc element to another. If additional connections exist between the disc elements, such as the disc element connection areas described in more detail below, these connection areas can be designed in such a way that the rotor would be sufficiently stable solely due to these connection areas. In this case, the shape of each cooling element can be optimized for maximum cooling performance, regardless of its mechanical properties. In principle, the cooling element can then have any shape that fits between the disc elements. However, to optimize heat dissipation, a person skilled in the art would choose a shape with a particularly large surface area oriented towards the internally ventilated area, as this ensures greater heat dissipation.It is generally preferred if the cooling element has at least one straight section extending from one disk element to another, which is aligned parallel or inclined to the axis of rotation. This ensures that the cooling element can withstand mechanical and thermal loads appropriately. In this case, additional connections between the disk elements, such as the disk element connection areas described in more detail below, can be completely or partially omitted, while still achieving outstanding mechanical strength of the rotor. A straight section extending from one disk element to another exists if at least one straight line can be found that runs completely within the section from a transition point of the section into one disk element to the transition point of the section into the other disk element.A section is aligned parallel to the axis of rotation if a straight line can be found that is also parallel to the axis of rotation. A section is aligned inclined to the axis of rotation if at least one straight line can be found that runs completely within the section from a transition point of the section into one disk element to a transition point of the section into another disk element, but no such straight line can be found that is also parallel to the axis of rotation.

[0024] In rotors particularly preferred according to the invention, the cooling element (3) comprises a microstructure obtainable by additive manufacturing, in particular by 3D printing, e.g., by binder jetting. This is preferably a carbon-based microstructure. This allows the geometry of the internally ventilated cooling zone to be optimized with regard to heat dissipation, without having to consider manufacturing-related limitations of subtractive manufacturing processes. This enables the economical generation of intricate structures with undercuts in all spatial directions and of open-pore structures for the flow of fluids, as are also found in open-pore foamed materials. For this purpose, the person skilled in the art uses computer-aided optimization (CAO), in particular computer-aided topology optimization. Such a microstructure of the cooling element is obtained in a variety of ways, e.g.,when the method for manufacturing rotors according to the invention, as described in WO 2017 / 089494 A1, is modified. In this process, according to WO 2017 / 089494 A1, claim 1, steps a) to d), a green body with the desired shape of the cooling element of a rotor according to the invention is produced. The green body can be produced in any desired shape, e.g., in the form of a rod, a rib structure, a grid, a bar structure, a three-dimensional truss structure, or in the form of the joining core described in more detail below, which is also part of the present invention.

[0025] Depending on the shape of the green body produced according to WO 2017 / 089494 A1, claim 1, steps a) to d), different further procedures can now be carried out to obtain a rotor according to the invention.

[0026] If the green body formed according to WO 2017 / 089494 A1, claim 1, steps a) to d), is also a joining core according to the invention, the green body can be further processed according to the method described in DE 102 34 400 B3. In the method of DE 102 34 400 B3, the joining core according to the invention is used instead of the core described therein, and the rotor according to the invention is obtained according to steps two, three, four, five, and six of claims 1, 2, and 8 of DE 102 34 400 B3. In step six, however, the material derived from the joining core is also infiltrated with silicon.

[0027] If the green body is not a joining core according to the invention, but is, for example, a rod, a rib structure, a grid, a bar structure, or a spatial truss structure, the green body cannot be used in place of the core in the method of DE 102 34 400 B3. Instead, disc element green bodies are formed from the material described in DE 102 34 400 B3 and cured. The green bodies formed according to WO 2017 / 089494 A1, claim 1, steps a) to d) are applied to one side of one of the cured disc element green bodies, for example, bonded with a phenolic resin. The green bodies can also be partially incorporated into the disc element green bodies, for example, the green bodies can be pressed into the disc element green bodies if the disc element green bodies are not yet fully cured. The other disc element green body is then applied to the applied green bodies, for example, bonded with a phenolic resin.Subsequently, carbonization and silicification are carried out as described in WO 2017 / 089494 A1, claim 1, steps e) and f).

[0028] As an alternative to 3D printing, e.g. binder jetting, selective laser sintering (SLS) or selective laser melting (SLM) can be used.

[0029] Preferably according to the invention, the cooling zone (1) comprises a channel that runs through the cooling element (3) from a cooling element opening (5) closer to the axis of rotation to a cooling element opening (6) further away from the axis of rotation. This ensures that the surface of the entire channel (and optionally also the surface of the entire internally ventilated cooling zone) acquires the surface properties controlled by the manufacturing process (e.g., 3D printing) and that the heat dissipation properties can be improved accordingly.

[0030] The rotors according to the invention can have a cooling structure, such as the bar structures, rib structures, and / or grids already described above in connection with additive manufacturing and 3D printing. The surface of the cooling structure can have a freeform shape. The cooling structure can, for example, be a gyroidal structure. A freeform surface is understood to be a surface that is, for example, multiply curved. The term grid is intended here to encompass three-dimensional grids as well as essentially two-dimensional grids. One type of grid has a multitude of channels, for example, round channels, that are open radially inwards and outwards. However, the cooling structure is not limited to bar structures, rib structures, and / or grids. Any structure consisting of a multitude of bars, ribs, and / or grids, arranged chaotically or in an ordered manner, constitutes a cooling structure.The bars, ribs, and / or grids, especially the bars, can intersect each other. A cooling structure refers specifically to any regular structure in which the structural areas present in one volume element are found identically or as mirror images in another volume element of the cooling structure. Such cooling structures, particularly those produced using additive manufacturing or 3D printing, allow for the creation of particularly large surface areas in the internally ventilated cooling zone, thereby further improving heat dissipation. For example, the cooling structure can be a lattice girder structure comprising two parallel bars that intersect two further parallel bars at their points of intersection. Alternatively, the cooling structure can be a three-dimensional truss structure.A spatial truss structure is defined as any structure in which members are arranged triangularly, whereby some of the members (especially those functioning as chords) may be planar. A more delicate design of the cooling structures can increase the surface area and thus enhance turbulence and the associated heat input into the airflow.

[0031] The cooling structure can be completely enclosed by the cooling element and extend, for example, from one wall of the cooling element to another wall of the cooling element, with the cooling element being connected to each of the disk elements via one of the walls. This enables particularly simple manufacturing of the rotor, since the joining core can then be used instead of the core described in DE 102 34 400 B3. Such a rotor is obtained if a joining core according to the invention, produced, for example, by means of 3D printing, is used to manufacture the rotor, as exemplified in Fig. 3 shown.

[0032] The joining cores described herein are preferably available by means of 3D printing or at least partially formed by 3D printing.

[0033] Alternatively, the cooling structure can be formed by a multitude of cooling elements and the two disc elements, with the cooling elements connecting the disc elements. For example, the disc elements can be the chords on both sides of a frame structure, e.g., a truss, and the cooling elements can be the connecting members. This is in Figures 4 and 5 Shown as an example of a frame structure with a large number of parallel bars.

[0034] In certain rotors, part of the cooling structures can be completely enclosed by a cooling element, and another part of the cooling structures can be formed by a multitude of cooling elements and the two disk elements.

[0035] The ratio of the rotor's inner surface area to its outer surface area can be at least 1:1, preferably at least 1.5:1, more preferably at least 2.5:1, particularly preferably at least 4:1, and most preferably at least 8:1. Cooling structures with extremely large surface areas can be created, especially through 3D printing, so that the ratio of inner surface area to outer surface area of ​​over 5:1 currently achieved in motorsports can be reached or even exceeded by the present invention. The inner surface of the rotor is the surface of the rotor oriented towards the internally ventilated cooling zone. It is available for cooling. The outer surface of the rotor is the sum of the surfaces of the two essentially parallel, planar, outwardly oriented surfaces of the rotor.This further increases the cooling effect of the internally ventilated cooling zone, allowing the rotors and brake units to be designed to be even smaller and lighter overall.

[0036] A person skilled in the art can experimentally determine the minimum distances or diameters that must be maintained in the cooling structures to prevent the cavities within the cooling structure from filling with liquid silicon under the given infiltration conditions. The smallest distance between two cooling structure areas adjacent to a cavity is preferably greater than 2 mm, since the tendency of silicon to fill the cavities decreases with increasing distance.

[0037] The internally ventilated rotor can have a disk element connection area that joins the disk elements, where the mean volume fraction of fibers in the disk element connection area corresponds to the mean volume fraction of fibers in the disk elements. The statement that the mean volume fraction of fibers in the disk element connection area corresponds to the mean volume fraction of fibers in the disk elements means that the two mean volume fractions of fibers differ by at most a factor of 1.5. That is, one mean volume fraction of fibers is at most 1.5 times higher than the other mean volume fraction of fibers. Such disk element connection areas can be designed using the [method / method / method - context needed]. Fig. 3The joining core shown is formed. This core has 10 evenly distributed recesses around its circumference, through which the mass used to form the disk elements extends directly from one disk element into the other. This creates an (additional) material-bonded connection between the two disk elements, further increasing the mechanical strength of the rotor.

[0038] The present invention also relates to a joining core for the manufacture of an internally ventilated rotor according to the invention, wherein the joining core has a structure that is sufficiently porous, or becomes sufficiently porous by pyrolysis (e.g. treatment at at least 400 °C in an N2 atmosphere) to be joined with a molten metal or semimetal, e.g. silicon, to be able to be infiltrated and has a surface (14) that coincides with the outer shell surface of a hollow cylinder and / or has a surface (15) that coincides with the inner shell surface of the hollow cylinder, characterized in that the structure is obtained by additive manufacturing.

[0039] The structure, which is sufficiently porous to be infiltrated with a molten metal or semimetal, e.g. silicon, can be formed, e.g., according to WO 2017 / 089494 A1, claim 1, steps a) to e).

[0040] A structure which becomes sufficiently porous by pyrolysis to allow infiltration with the molten metal or semimetal, e.g. silicon, can be formed according to WO 2017 / 089494 A1, claim 1, steps a) to d).

[0041] Because the joining core according to the invention has a surface that coincides with the outer surface of a hollow cylinder and / or a surface that coincides with the inner surface of the hollow cylinder, the joining core can be used particularly well for manufacturing the rotor according to the invention. For manufacturing the rotor, the joining core can then be used particularly advantageously in a press mold, which is bounded externally by a cylindrical outer wall and internally by a cylindrical inner wall. The mold itself then has the shape of the hollow cylinder. At least one of the surfaces of the joining core according to the invention then rests against one of the walls of the mold, so that the molding compound containing fibers and resin does not come into contact with this surface of the joining core during the subsequent pressing step.

[0042] The surface geometry required for the joining core according to the invention allows for the particularly elegant formation of an internally ventilated zone. This is especially true if the joining core has a cavity and the cavity is open to one of the surfaces coinciding with a shell surface, or to both of these surfaces. Since the molding compound does not come into contact with this surface(s) of the joining core, it cannot enter the cavity through the opening(s) in this surface or through the openings in these surfaces of the cavity. Therefore, the cavity is not filled by the molding compound and is subsequently available as (part of) the internally ventilated cooling zone(s).

[0043] The joining core according to the invention can be ring-shaped. An example of a ring-shaped joining core is shown in Figure 3This further simplifies the manufacturing of the rotor, as the risk of the joining core slipping during the pressing of the molding compound is reduced to a minimum, making the production of the rotor particularly easy and with the smallest possible scrap.

[0044] The joining core can be composed of joining core segments. This means that the joining core can be divided into several (at least 2, preferably at least 4, particularly preferably at least 6, very preferably at least 8, e.g., at least 10; preferably at most 100, particularly preferably at most 50, e.g., at most 36) joining core segments without cutting through the joining core material. Joining core material is understood to be the material that, as defined above, is sufficiently porous or becomes sufficiently porous through pyrolysis to be infiltrated with a molten metal or semimetal, e.g., silicon. The joining core segments can be axial segments, as shown in Figure 6 shown. This does not preclude additional tangential segmentation, which is shown in Figure 7 As shown. The joining core segments can therefore be axial segments and / or tangential segments.

[0045] Preferably, the segment surfaces of adjacent segments are shaped such that the contours of the segment surfaces interlock. This secures the joining core segments against slippage in a radial or tangential direction. Consequently, the joining core constructed from joining core segments is easier to handle, and the amount of scrap in the subsequent production of rotors according to the invention is reduced.

[0046] Segments can interlock, for example, like puzzle pieces.

[0047] Adjacent segments can also have undercuts. An undercut allows the adjacent segments to be connected. Connecting them can, for example, involve inserting one segment into an adjacent segment.

[0048] A further advantage is that joining core segments enable more efficient use of the 3D printer's build volume, for example, by alternating the segments in opposite directions. With non-segmented joining cores formed as a single piece, the build volume cannot be utilized as effectively. Furthermore, individual joining core segments better compensate for thermal stresses because the continuous contact areas with adjacent materials, which have different coefficients of thermal expansion, are smaller. Consequently, segmentation simultaneously increases the efficiency of additive manufacturing of joining cores and reduces scrap in the subsequent production of rotors according to the invention.

[0049] A joining core constructed from joining core segments can have openings between the joining core segments that extend through the joining core, from one surface of the joining core to the other surface of the joining core. This has the advantage that these openings can be filled during the subsequent manufacturing of rotors according to the invention, thereby creating disk element connection areas, which are described in more detail elsewhere herein. In this way, the proportion of more solid connection areas and the proportion of cooling elements with better heat dissipation can be specifically adjusted, depending on whether higher stability or cooling performance requirements are placed on a particular rotor according to the invention.

[0050] This also applies with additional tangential segmentation. The mechanically more stressed disc element connection areas can then be selectively formed between inner joining core segments located closer to the axis of rotation and outer joining core segments located further away from the axis of rotation, precisely where brake pads are pressed onto the rotor. Conversely, the cooling elements, which are part of the joining core segments, can be arranged radially further inwards and outwards, i.e., where the stress from the pressed-on brake pads is lower, thus allowing for greater optimization of cooling performance.

[0051] It is possible with minimal effort to selectively arrange the joining core segments radially inside and outside by supplementing a conventional core, such as the compressible core described in patent DE 102 34 400 B3, with joining core segments according to the invention. The joining core segments can, for example, occupy a portion of the space radially inside and outside that would otherwise be occupied by the compressible core.

[0052] Radial segmentation can be achieved particularly easily in a mold described in DE 601 15 964 T2. Core segments (e.g., core segments obtainable by means of 3D printing) can be attached to the pin elements described therein. The pin elements are brought into a working position as described in DE 601 15 964 T2. The lengths and shapes of the pin elements and core segments can be coordinated so that moving the pin elements into the working position brings the core segments into the position they are intended to occupy in the resulting rotor or brake pad. When the pin elements are returned to their rest position, the core segments remain in the desired position. In this position, they are held by the composite material mixture that has been pressed into the mold and at least partially cured therein.Here, the term "core segment" is used because it is inserted via the pins, and the core segments themselves are not joined together in this case. The syllable "join" was omitted here solely for this reason.

[0053] Each joining core segment or core segment can have a cooling structure as described above. For example, it can have any combination of ribs, bars, and grids.

[0054] Regardless of whether the joining core is composed of joining core segments or not, the surfaces of the joining core, particularly those oriented axially, can have joining core recesses. During the manufacture of a rotor according to the invention, the material of the subsequent disk elements engages in these joining core recesses. This ensures an even stronger connection between the disk elements and the cooling element, which is based on the joining core. Consequently, the stability of the rotor can be further increased.

[0055] One wall of the core or cooling element can be curved (e.g., bent or corrugated). This has the advantage of better compensating for thermally induced stresses that can occur in the rotor during braking or even during infiltration with liquid silicon during rotor manufacturing. Despite the overall very low elastic deformability of the cooling element material or the core material, curvatures can reduce thermally induced stresses.

[0056] The invention also relates to a set comprising the joining core according to the invention and a press mold with a hollow cylindrical recess, wherein one surface of the recess coincides with the outer lateral surface of the hollow cylinder and another surface of the recess coincides with the inner lateral surface of the hollow cylinder.

[0057] According to the invention, the at least one cooling element of the rotor has a lower average volume fraction of fibers than the disk elements. Preferably, the average volume fraction of fibers in the cooling element does not exceed 40%. Preferably, the average volume fraction of fibers in the disk elements does not fall below 20%. The average volume fraction of fibers in the cooling element can, for example, be 0 to 40%. The average volume fraction of fibers in the disk elements can, for example, be 5 to 70%. It has been shown that this results in very high mechanical strength and, at the same time, particularly efficient heat dissipation. To determine the average volume fractions of fibers, the rotor, including the disk element(s) and cooling element(s), is cut through, the cut surfaces obtained from the cutting are ground, and the fiber content is determined visually (e.g., by measuring the thickness of the fibers).(using a microscope), the proportion of the cut surface area occupied by fibers is determined. If the fibers are not completely homogeneously distributed within the cooling and / or disc element, the rotor, including disc element(s) and cooling element(s), is cut multiple times, and all cut surfaces are included in the determination of the respective average volume fractions.

[0058] A transition from disc elements to cooling elements can be identified by the fact that, due to the manufacturing process, the material composition at the transition point differs from that of the directly adjacent disc elements and cooling elements. This is because precursors of cooling elements and disc elements are joined during the manufacturing process and only subsequently bonded together through metal or silicon infiltration. The respective areas for which the average volume fraction of fibers is to be determined are therefore sharply defined by the transitions. If such sharp transitions are not present, the point at which the volume fraction of fibers decreases most significantly is used instead to define the boundaries.Those areas with the lower volume fraction of fibers are then considered to belong to the cooling element with less fiber, and those areas with the higher volume fraction of fibers are then considered to belong to the disc element with more fiber.

[0059] Here, "fiber" preferably refers to carbon fiber. However, other high-temperature-resistant fibers known to experts are also conceivable.

[0060] The cooling element surfaces oriented towards the internally ventilated cooling zone can have a higher proportion of ceramic, e.g. silicon carbide, than the disc elements.

[0061] Disc elements can have perforations, such as perforated holes, extending from the surface of the disc elements into the internally ventilated cooling zone. This further increases cooling performance. Additionally, water and brake dust are drawn into the cooling channel through the perforations during braking, thus keeping the friction surface dry and clean.

[0062] In particularly preferred rotors according to the invention, a brake disc hub is attached via several, e.g., 4, 6, 8 or 10, mounting points. At each mounting point, a fastening element is inserted into the rotor. Each fastening element extends into a disc element connection area.

[0063] The invention also relates to the use of the internally ventilated rotor according to the invention as a brake disc for aircraft, trains, elevators, cable cars, motorcycles, passenger cars, buses, trucks, racing vehicles, quads, multi-purpose vehicles (MPVs), all-terrain vehicles (ATVs), for industrial applications, e.g. for cranes or paper machines, as a brake pad, as a clutch disc, as a grinding wheel carrier, as a heat sink, as a pump impeller and / or as a turbine component.

[0064] The invention is illustrated by the following figures, without being limited thereto. Figure 1 shows a first rotor according to the invention. Figure 1A shows a section of Figure 1 Figure 2 shows a view of the rotor according to the invention. Figure 1 , wherein part of the upper disc element 2 is not shown. Figure 3 shows an joining core according to the invention for producing the in Figure 1 and 2Figures 3A and 3B of the rotors shown depict excerpts from Figure 3 Figure 4 shows a second rotor according to the invention, wherein part of the upper disk element 2 is not shown. Figure 5 shows a third rotor according to the invention. Figure 6 shows a connecting core according to the invention constructed from segments. Figure 7 shows segments for a further connecting core according to the invention.

[0065] The in Figures 1, 1A and 2 The rotor shown comprises two interconnected disk elements. 2, an internally ventilated cooling zone 1 between the disc elements 2 and at least one (using the in Fig. 3 , 3A and 3B cooling element formed by the shown joining core 3. The cooling element 3 It exhibits a carbon-based microstructure obtained through 3D printing. The cooling zone 1 It is open inwards and outwards in a radial direction and comprises a multitude of channels, each of which passes through the cooling element.3 from a cooling element opening closer to the axis of rotation 5 to a cooling element opening further away from the axis of rotation 6 The rotor has several cooling structures. 10 in the form of rib structures, each with 5 Spacing of the ribs ensures that the channels are limited by the ribs of the cooling structure. This allows air to pass through the cooling zone. 1 flow. Each rib represents a straight section which contains the cooling element and is connected to a disc element. 2 to the other disc element 2 It runs straight. The cooling element 3 connects the disc elements 2 and is thus arranged in such a way that heat is drawn away from the cooling element. 3 directly onto the area in the cooling zone 1 The air present can be transferred.

[0066] In the rotor of the Figures 1, 1A and 2 is the cooling structure 10 completely from the cooling element 3It encompasses. It extends from a wall 8 of the cooling element 3 to another wall 9 of the cooling element 3, where the cooling element 3 over one of the walls each 8, 9 with one of the disc elements each 2 is connected. The ratio of the rotor's inner surface area to its outer surface area is greater than 1.5:1. The in Figures 1, 1A and 2 The rotor shown has ten disk element connection areas. 7 on, which the disc elements 2 connect as well.

[0067] Unlike the rotor of the Figure 1 and 2 is the rotor Figure 4 and at the rotor of the Figure 5 the cooling structure 10 a frame structure. The frame structure is constructed with the participation of a large number of cooling elements. 3 and the two disc elements 2formed. The disc elements form the chords on both sides of the respective frame structure.

[0068] The rotor of Figure 4 The cooling elements are rods aligned parallel to each other and parallel to the axis of rotation, which do not touch or cross each other and can be easily manufactured without 3D printing. The ratio of the rotor's inner surface area to its outer surface area is greater than 1.5:1.

[0069] The rotor of Figure 5 The frame structure consists of numerous intersecting bars, alternately inclined at 45° and -45° relative to the axis of rotation. The ratio of the rotor's inner surface area to its outer surface area is greater than 3:1.

[0070] In the three rotors shown in the figures, the disc elements are silicon carbide carbon fiber composite friction discs, and the cooling elements are silicon carbide cooling elements. All cooling elements 3They therefore have a lower average volume fraction of fibers than the disc elements. 2.

[0071] Figure 3 shows a ring-shaped joining core 13 for the production of a in Figure 1 and 2 The rotors shown, according to the invention. The joining core 13 is formed according to WO 2017 / 089494 A1, claim 1, steps a) to d) and has a microstructure that becomes sufficiently porous through pyrolysis to allow infiltration with silicon. The joining core 13 has a surface 14 on, which coincides with the outer surface of a hollow cylinder and forms a surface 15 on, which coincides with the inner surface of the hollow cylinder (see Figures 3A, 3B The hollow cylinder is in Figure 3 Shown as a dashed line. Joining core 13 It has a cavity. The cavity is adjacent to both surfaces. 14, 15open. In the case shown here, the openings of the cavity are in the surfaces. 14, 15 so large that from the surfaces 14, 15 Only the two edges remain, which are in Figures 3A and 3B They are clearly visible.

[0072] Figure 6 shows another embodiment of the ring-shaped joining core. 13. This one is made of joining core segments. 16 The assembly is constructed. To illustrate the shape of the individual joining core segments, one of the joining core segments is shown outside the plane of the joining core. In the embodiment shown here, each joining core segment has a first segment surface. 17 and a second segment surface 18 Both segment surfaces are shaped so that their contours interlock. This stabilizes the joining core segments. 16 against slippage in a radial or tangential direction. In the example shown here, both segment surfaces exhibit17, 18 Convex and concave areas. Convex areas of the first segment surface. 17 of a joining core segment 16 engage in concave areas of a second segment surface 18 a directly adjacent joining core segment 16, and vice versa. The two surfaces oriented upwards and downwards in the axial direction in the figure also have elongated joining core recesses. 19 and round joining core recesses 20 The arrangement of recesses above and below ribs or bars has the advantage that the wall thickness in the area of ​​the transition to the rib can be kept essentially the same as in other wall areas of the cooling element. The reduction of material accumulations promotes thermal expansion compensation between the materials and thus reduces internal stresses.

[0073] The in Figure 7 shown, larger and smaller joining core segments 16are derived from radially outer and inner areas of the joining core segments, which are in Figure 6 are shown. During the in Figure 6 Since the joining core 13 shown is axially segmented, an additional segmentation in the radial direction can be carried out, which is Figure 7 as indicated. In rotors according to the invention, the smaller joining core segments can 16 Therefore, define cooling element openings closer to the axis of rotation. The larger joining core segments 16 can define cooling element openings further away from the axis of rotation. Reference symbol list

[0074] 1 Internally ventilated cooling zone 2 Disc element 3 Cooling element 5 Cooling element opening closer to the axis of rotation 6 Cooling element opening further away from the axis of rotation 7 Disc element connection area 8, 9 Walls of the cooling element 10 Cooling structure 13 Joining core 14 Surface coinciding with the outer shell surface of a hollow cylinder 15 Surface coinciding with the inner shell surface of a hollow cylinder 16 Joining core segment 17 First segment surface 18 Second segment surface 19 Elongated joining core recesses 20 Rounded joining core recesses

Claims

1. Internally ventilated rotor comprising at least two disc elements (2) connected to one another and a joining core (13) with an internally ventilated cooling zone (1) and a cooling element (3) between the disc elements, wherein the cooling element (3) connects the disc elements, in such a way that heat is directly transferred from the cooling element (3) to the air in the cooling zone (1), and wherein the disc elements and the cooling element (3) contains fibers, the cooling element (3) having a lower average volume fraction of fibers than the disc elements (2), and wherein the cooling zone (1) is open in the radial direction inwards and outwards, so that air can flow through the cooling zone (1), characterized in that the joining core (13) has a structure that is produced by additive manufacturing.

2. Internally ventilated rotor according to claim 1, wherein the cooling element (3) has at least one section which runs straight from one disc element (2) to the other disc element (2) and is oriented parallel or inclined to the axis of rotation.

3. Internally ventilated rotor according to claim 1, wherein the mean volume fraction of fibers of the cooling element (3) is 0 to 40% and / or the mean volume fraction of fibers of the disc element (2) or the disc elements (2) is 5 to 70%.

4. Internally ventilated rotor according to claim 1, wherein the cooling element (3) comprises a structure obtainable by additive manufacturing, for example by 3D printing.

5. Internally ventilated rotor according to claim 1, wherein the cooling zone (1) comprises a channel which runs through the cooling element (3) from a cooling element opening (5) closer to the axis of rotation to a cooling element opening (6) further away from the axis of rotation.

6. Internally ventilated rotor according to claim 1, having a cooling structure (10) selected from bar structures, rib structures, and / or grids.

7. Internally ventilated rotor according to claim 6, wherein the cooling structure (10) is completely surrounded by the cooling element (3) and extends, for example, from one wall (8) of the cooling element (3) to another wall (9) of the cooling element (3), wherein the cooling element (3) is connected to one of the disc elements (2) via one of the walls (8, 9).

8. Internally ventilated rotor according to claim 6, wherein the cooling structure (10) is formed with the participation of a plurality of cooling elements (3) and the two disc elements (2), the cooling elements (3) connecting the disc elements (2).

9. Internally ventilated rotor (1) according to claim 1, wherein the ratio of the inner surface of the rotor (available for cooling) to the outer surface of the rotor (available for braking) is at least 1:1.

10. Internally ventilated rotor (1) according to claim 1, having a disc element connection area (7) which connects the disc elements (2), wherein the mean volume fraction of fibers in the disc element connection area (7) corresponds to the mean volume fraction of fibers in the disc elements (2).

11. Joining core (13) for the production of an internally ventilated rotor according to one of the preceding claims, wherein the joining core (13) has a structure that is porous or becomes porous by pyrolysis to be infiltrated with a molten metal or semi-metal, e.g. silicon, and has a surface (14) which coincides with the outer jacket surface of a hollow cylinder and / or has a surface (15) which coincides with the inner jacket surface of the hollow cylinder, characterized in that the structure is produced by additive manufacturing.

12. Joining core (13) according to claim 11, having a cavity, the cavity being open towards one of the surfaces (14, 15) or towards these two surfaces (14, 15).

13. Use of the internally ventilated rotor according to one of claims 1 to 10 as a brake disc for aircraft, trains, elevators, cable cars, motorcycles, passenger cars (cars), buses, trucks (lorries), racing vehicles, quads, multi-purpose vehicles (MPV), all-Terrain Vehicles (ATV), for industrial applications, e.g. for cranes or for paper machines, as a brake lining, as a clutch disc, as a grinding wheel carrier, as a heat sink, as a pump impeller and / or as a turbine component.