Racing bicycle hub

Abstract

Disclosed is a racing bicycle hub (1) designed as an inner bearing ring for a rolling bearing, wherein the racing bicycle hub (1) has at least one raceway (4) for rolling elements of the rolling bearing on the outside, and wherein at least one non-functional surface (12) of the racing hub (1) is laser-hardened.

Description

Technical field

[0001] The present invention relates to a racing bicycle hub according to the preamble of claim 1. Technical background

[0002] In motorsports, wheel hubs are subjected to particularly high loads due to the accelerations that occur there. Furthermore, rims mounted on the wheel hubs must be quickly interchangeable and are therefore usually attached to the hub with only a single bolt and nut. This single bolt and nut connection is also subjected to considerable stress during operation. To withstand these stresses, the cycling hubs are hardened. This is typically achieved using an induction hardening process or a conventional method such as martensitic and / or bainitic hardening.

[0003] To ensure that the functional surfaces of the racing hub—that is, the surfaces serving as the raceway or sliding surface—can withstand the stresses of operation, these functional surfaces have traditionally been induction hardened. While this is a cost-effective process, non-functional surfaces, such as the thread for the single locking nut, are not hardened. This leads to an increased risk of wear and deformation of these surfaces.

[0004] State-of-the-art heat treatments, such as martensitic hardening, bainitic hardening, case hardening, nitriding or induction hardening, also have the following disadvantages: - Batch processes (except induction hardening) without individual piece flow - Large appliances / ovens needed for large hubs (which are difficult to obtain) - Large distortion leads to large allowances for the soft component and costly rework. - Significant effort required for parts handling and logistics Surface damage requires hard machining to remove damaged surfaces (e.g., decarburization, oxidation, etc.). - Special, partial tooling costs and associated costs (e.g. inductors for induction hardening) - Long changeover times when switching production parts - Selective hardening is not possible (exception: induction hardening) - Space requirements for heat treatment plants

[0005] The object of the present invention is therefore to provide a racing hub that is inexpensive to manufacture and can withstand the stresses of racing in its entirety. Summary of the invention

[0006] This problem is solved by a racing hub according to claim 1.

[0007] The racing wheel hub is designed as an inner bearing ring for a rolling bearing and has at least one raceway on its outer surface for the rolling elements of the bearing. The functional surfaces of the racing hub can be hardened by known heat treatment processes, such as induction hardening. In this context, a functional surface of the racing hub is understood to be a raceway or sliding surface.

[0008] In contrast to previous racing hubs, where the non-functional surfaces are either also induction-hardened or not hardened at all, at least one of the non-functional surfaces of the racing hub proposed here is laser-hardened.

[0009] In this context, a non-functional surface is understood to be any surface other than the raceway or sliding surface, i.e., all non-raceway surfaces. Non-functional surfaces can, for example, be part of a thread used to attach the rim to the bicycle hub using a screw-nut connection, or they can be other surfaces that need to be wear-resistant, protected against deformation, or have a certain thickness, such as surfaces onto which other components are shrunk or attached, or surfaces that come into contact with other components.

[0010] By using laser heat treatment to harden at least one non-functional surface, this surface can be heated and hardened very precisely. Furthermore, the laser hardening process requires no post-processing and can be carried out as the final manufacturing step in a single operation or in combination with soft machining, e.g., on a lathe. The use of laser hardening also overcomes the disadvantages mentioned above.

[0011] In laser hardening, steel components are locally heat-treated to create a martensitic microstructure through rapid laser heating followed by cooling, primarily by heat conduction. If required for geometric reasons and / or due to the limited hardenability of the steel used, additional quenching media (e.g., compressed air or water) can be employed to increase the quenching rate.

[0012] Laser hardening is characterized by limited energy / heat input, resulting in low energy consumption and associated low CO2 emissions, minimal distortion, and limited or no surface oxidation. This allows for the elimination of subsequent hard machining steps to remove surface defects such as oxide layers, decarburized surfaces, and scale, which would occur with conventional hardening processes, and the integration of the hardening process into the soft machining process. This can reduce throughput time as well as handling and logistics costs in the production chain.

[0013] Furthermore, laser hardening is characterized by high energy density and short processing times. It is also advantageous that only a small volume is affected, or only a small portion of the workpiece cross-section is treated, and that no process gases are required. As mentioned above, laser hardening also eliminates the need for quenching the workpiece after heating, as quenching occurs primarily through heat conduction within the component. This has the advantage that no quenching medium, and therefore no pumps for quenching or cooling the system, are required.

[0014] Furthermore, the same laser source and optics can be used for different workpiece geometries, so that part-specific tooling can be avoided.

[0015] Another advantage of laser hardening is that it results in very little to no distortion of the bearing component, thus partially or completely eliminating the need for costly post-processing, especially complex hard machining. This also means that less material is required due to reduced deformation, resulting in better material utilization and further savings in costs and energy / CO2 emissions.

[0016] Furthermore, the laser hardening process can be integrated into the soft machining process (e.g., turning, etc.), i.e., the machining before the actual hardening, and / or the hard machining process (e.g., grinding, honing), i.e., the machining after hardening. Integration into existing machines is even possible. In addition, a flexible laser hardening unit can be integrated into the soft machining process—as well as into the hard machining unit—which can reduce cycle time and significantly increase productivity.

[0017] Since not only the functional but also the non-functional surfaces are hardened, wear particles and surface damage from relative movement or incorrect operation of the racing hub can be more comprehensively avoided. Furthermore, the combination of induction-hardened and laser-hardened surfaces can reduce warpage of the racing hub, which in turn requires less machining and thus saves costs and energy.

[0018] In particular, the functional surfaces may have undergone induction hardening. The other surfaces remain unaffected by the induction heat treatment and retain the initial hardness of the softer component (e.g., 20–40 HRC). Typical steel grades are all hardenable steels with the following exemplary chemical composition: carbon (0.40–1.10 wt.%), silicon (0.15–0.35 wt.%), manganese (0.60–1.10 wt.%), chromium (0.30–2.00 wt.%), and molybdenum (0.10–0.75 wt.%).

[0019] The laser hardening process of the non-functional surface(s) results in a shallow hardening depth (up to a maximum of 2 mm) to create a hard and wear-resistant layer on these surfaces, which, unlike raceways, are not subject to rolling contact but rather sliding contact. The laser hardening process increases wear resistance to prevent excessive wear and strength to prevent excessive plastic deformation.

[0020] According to one embodiment, the non-functional surface is a thread on the outside of the racing wheel hub, designed to receive a nut for securing a wheel. The thread is subject to sliding contact at the thread crest and flanks, as well as a certain contact pressure on the flank when the nut is tightened. Excessive wear, plastic deformation, and breakage of the thread or parts thereof can be prevented by targeted laser hardening, for example, to a hardness > 45 HRC.

[0021] Alternatively, the non-functional area could be other surfaces of the racing hub besides the track. These include, for example: - Sealing surfaces: The sealing surfaces are subject to sliding contact against the seal and should have a certain hardness to prevent wear, in particular > 50 HRC - Surfaces to which other components are attached or shrunk: These surfaces should also be hardened (especially to >45 HRC) to prevent cold galling due to micro-movements between the two components and wear marks during assembly. - Outer diameter, side surface / shoulder of an outer ring - Inner diameter, side surface / shoulder of an inner ring

[0022] According to a further embodiment, the thread is at least partially hardened. In particular, the thread tips can be laser-hardened, and the thread flanks can transition from the laser-hardened tips to a non-hardened area within the thread. Alternatively or additionally, a first turn of the thread can be laser-hardened.

[0023] By hardening the first thread, the area where a nut is initially placed to secure the rim to the racing hub can be particularly hardened. This area is subject to especially high loads on the thread (due to the nut being inserted). Hardening this initial section of the thread can prevent wear and deformation of the racing hub during rim installation, especially at the beginning when the nut is being fitted. Furthermore, the thread tips can be hardened, as they, like the first thread, are also subjected to higher loads compared to the thread flanks. Therefore, there can be a transition between a hardened area (> 50 HRC) and an unhardened area (20-35 HRC) within the thread.

[0024] As explained above, the case depth of at least one non-functional, laser-hardened surface can reach a maximum of 2 mm, and in particular a maximum of 1.5 mm. Case depth is defined as the area in which, due to heat input from the laser, a phase transformation of the base material occurs from a ferritic microstructure to a martensitic microstructure. In other words, laser hardening of at least one non-functional surface creates a transformed surface layer extending across the case depth, to which the untransformed microstructure is attached.

[0025] The hardness of at least one non-functional, laser-hardened surface can be greater than 45 HRC, and in particular greater than 50 HRC. As explained above, this hardness is sufficient to protect at least one non-functional surface from wear.

[0026] According to a further embodiment, the surface of the at least one non-functional, laser-hardened area has a texture. The texture can, for example, be designed to increase the coefficient of friction of the surface. Furthermore, the texture can form lubrication grooves and / or a lubricant reservoir.

[0027] As mentioned above, laser hardening involves a microstructural phase change, leading to a change in the specific volume or density of the physical phases, for example, during the transformation into martensite and / or bainite. The hardened and transformed areas have a larger volume than in the initial phase and result in a raised surface on the laser-hardened surface in the micrometer range.

[0028] In this process, surface areas with deeper hardening rise higher than those with shallower or unhardened hardening. This allows for the application of a specific surface texture and topology to the non-functional surface. Any number of surface areas with varying hardening depths can be incorporated, for example, to further refine the surface texture.

[0029] Alternatively, the texture can also be created by partial melting of the surface (cratering) or by internal residual stresses which can be caused by surface heat treatment.

[0030] As explained above, the differently hardened areas can be arranged in such a way that one area forms a lubricant reservoir and / or a lubricant groove, which is delimited by another area. This advantageously contributes to reduced wear at sliding contacts. Furthermore, this ensures that lubricant can be retained and / or directed to specific locations on the racing hub.

[0031] For example, a "golf ball topography" can be created to form lubrication pockets and thereby improve lubrication conditions. As mentioned above, this can be achieved either by selectively hardening local areas or by varying the hardening depth. The resulting depressions act as lubricant reservoirs.

[0032] This behavior or property can also be used to create textures for increased friction on non-functional surfaces, especially non-functional contact surfaces, in order to prevent relative movement (e.g., creep) between the racing hub and contact partners (housing / shaft). A positive fit or frictional fit with a very high coefficient of friction, which hinders the relative movement of the racing hub and its counterpart in application, can result in a lower press fit / reduced contribution of frictional engagement. This, in turn, leads to lower tensile stresses in the racing hub (e.g., racing hub shrunk onto shaft) and a longer component lifespan.

[0033] Therefore, an embodiment is also advantageous in which the at least one non-functional surface has a first surface area laser-hardened to a first hardening depth with a first coefficient of friction and a second surface area and / or third surface area hardened to a second, lower hardening depth with a second or third coefficient of friction, wherein the first coefficient of friction is higher than the second and / or third coefficient of friction.

[0034] By selectively increasing the coefficient of friction of the racing hub at specific points, the relative movement between the hub and a counterpart (e.g., a shaft, rim, or wheel) can be made more difficult during use. This increased friction, along with the specific surface texture, can result in a less tight fit and a reduced contribution to friction, leading to lower tensile stresses in the hub and a longer service life.

[0035] According to another embodiment, the laser-hardened area of ​​at least one non-functional surface is formed continuously.

[0036] This ensures that the non-functional surface, especially the thread, is completely smooth across its entire circumference, resulting in a uniform increase in friction and thus consistent power transmission. This can be achieved with one or more laser heads.

[0037] Alternatively, it can of course also be advantageous if the laser-hardened area of ​​at least one non-functional surface is designed as discrete surface area sections.

[0038] For example, a soft, non-laser-hardened area can be provided across the entire circumference between the start and end positions of a scan, or even multiple soft areas can be created, forming specific patterns. The hardening can, for instance, be configured as multiple rectangles / squares, multiple circular / oval dots, multiple triangles, or even as zigzag shapes, optionally with varying angles.

[0039] The patterns can include additional functions, such as the aforementioned lubricant reservoirs or grooves. However, they can also simply be designed as specific elements that, for example, visually identify the applicant as the manufacturer of the racing hub.

[0040] According to a further embodiment, the laser-hardened area has at least one soft spot or soft seam, wherein the soft spot / soft seam is arranged in an unloaded area of ​​the laser-hardened area and / or wherein the soft spot / soft seam is arranged perpendicular to a loading direction.

[0041] There can be one soft spot / seam or several soft spots / seams.

[0042] Such a soft spot / soft seam can also occur, for example, if an already hardened area is reheated. This can happen, for instance, if the laser scanning the surface to be hardened passes over areas of the surface that have already been heated and then cooled again. Such soft spots are not necessarily critical, especially in non-functional surfaces, as these are typically subjected to lower stresses, and localized, small-scale soft spots are not critical if the surface is otherwise hardened.

[0043] This significantly simplifies the hardening process, as it eliminates the need for complex plant technology or process control, especially for preheating, or similar measures that would be necessary for slip-free hardening, i.e., hardening without soft spots or soft seams.

[0044] In principle, the non-functional surface can be hardened by laser hardening with or without a soft seam.

[0045] The soft spot or soft seam is preferably aligned in the axial direction or perpendicular to the direction of loading.

[0046] In order to achieve a better load and stress distribution, according to another embodiment the soft seam can be executed at a different angle than parallel to the axial direction of the racing hub.

[0047] As explained above, functional surfaces of the racing hub can be induction-hardened. In particular, according to one embodiment, the raceway can have an induction-hardened raceway surface.

[0048] Induction hardening is an established surface hardening process. Compared to laser beam hardening, it allows for the relatively simple creation of slip-free hardened zones, even up to several millimeters deep. Equipment and induction tools are state-of-the-art and therefore readily available.

[0049] According to a further embodiment, the racing wheel hub has a soft zone between the induction-hardened raceway surface and the at least one non-functional, laser-hardened surface. This soft zone can arise as an unhardened area between the induction-hardened raceway surface and the at least one non-functional, laser-hardened surface. The soft zone can also arise from reheating an already hardened, in particular induction-hardened, area, especially by having the laser scanning the surface to be hardened pass over previously heated and cooled areas of the induction-hardened region.

[0050] The soft zone between the induction-hardened raceway surface and the laser-hardened surface has the following advantages: - Reduced energy consumption (CO2) by avoiding hardening of non-relevant areas (which do not require increased strength) - The original toughness remains unchanged, so that shock loads can be absorbed (not brittle martensite) - No mutual influence between the two heat treatments (heat influence)

[0051] Further advantages and advantageous embodiments are specified in the description, the drawings, and the claims. In particular, the combinations of features specified in the description and the drawings are purely exemplary, so that the features may also exist individually or in different combinations. Brief character description

[0052] The invention will now be described in more detail with reference to exemplary embodiments illustrated in the drawings. These exemplary embodiments and the combinations shown in them are purely illustrative and do not define the scope of protection of the invention. The scope of protection is defined solely by the pending claims.

[0053] They show: Fig. 1: A cross-sectional view of a racing bicycle hub; Fig. 2: A perspective detail view of a thread of the racing bicycle hub of Fig. 1; and Fig. 3: A schematic sectional view of a thread profile of the thread of Fig. 2. Detailed description of the invention

[0054] In the following, identical or functionally equivalent elements are marked with the same reference symbols.

[0055] Fig. Figure 1 shows a racing hub 1, which is designed as an inner bearing ring for a rolling bearing (not shown). For this purpose, the racing hub 1 has various surfaces 2 for the rolling bearing. These include, among others, a raceway 4 for the rolling elements of the rolling bearing and a seal seat 14 on which a seal for sealing the rolling bearing can be arranged. The raceway surface 4 is also referred to as the functional surface.

[0056] The functional surface 4 is arranged on a cylindrical section 10 of the racing hub. This section 10 is separated by a flange 6 from another section 8, which in turn has at least one non-functional surface 12, in this case a thread for receiving a nut (not shown).

[0057] This thread 12 can be used, for example, to attach a rim to the racing hub 1. However, when screwing on the required nut, the thread 12 is subjected to stresses that can damage it.

[0058] Up to now, the non-functional surfaces, such as the thread 12, have not been hardened, primarily for cost reasons; only the functional surface 4 has been hardened by an induction hardening process. This led to the problem described above of potential damage, for example, to the thread 12.

[0059] Therefore, at least one non-functional surface of the racing hub shown here is hardened using a laser hardening process. This has the advantage, among others, that the non-functional surface can be hardened in a targeted manner without any thermal influence on other, previously hardened areas.

[0060] The following refers to Fig. 2 and Fig. 3. A thread 12 is described in more detail as a non-functional surface. As in Fig. As shown in Figure 2, the thread 12 consists of several turns 16-1, 16-2, which form a thread pitch 12 as well as thread crests (16 in Fig. 3) comprising thread flanks 18 that transition into the thread 20. Preferably, the first turn 16-1 of the thread 12 is hardened. This first turn 16-1 is the turn with which a nut first comes into contact and is therefore subject to the highest loads and wear. Laser-hardening this first turn 16-1 prevents it from being subjected to severe wear and / or deformation during the tightening of a nut.

[0061] Furthermore, the laser hardening process allows the thread crests 16 to be hardened. The flanks 18 of the thread 12 transition from the laser-hardened crests 16 into a non-hardened area in the thread pitch 20. This is primarily due to manufacturing requirements and has the advantage that the crests 16, which are potentially subject to higher loads, such as the first thread pitch 16-1, are hardened, thereby reducing wear on the thread 12.

[0062] This transition from a hardened area to an unhardened area is also found in Fig. Figure 3 is shown as an example. As can be seen, the area of ​​the thread tips 16 (hatched area) is hardened and transitions into an unhardened area (white area). This transition can also be gradual.

[0063] As explained above, the laser hardening process enables very precise hardening of various non-functional surfaces. This is particularly advantageous in the area of ​​the thread 12, as it allows for the targeted hardening of only the tips 16, the first thread pitch 16-1, or other areas of the thread.

[0064] In summary, this is a racing hub which, due to the laser-hardened non-functional surfaces, has a longer lifespan compared to previous racing hubs. Reference symbol list 1 racing hub 2 surfaces for rolling bearings 4 Career 6 flange 8 first section 10 second section 12 threaded seat 14 Seal seat 16 thread tip 16-1, 16-2 turn 18 Thread flank 20 threads

Claims

Racing bicycle hub (1) which is designed as an inner bearing ring for a rolling bearing, wherein the racing bicycle hub (1) has at least one raceway (4) for rolling elements of the rolling bearing on the outside, characterized in that at least one non-functional surface (12) of the racing hub (1) is laser hardened. Racing bicycle hub according to claim 1, wherein the non-functional surface (12) is a thread on the outside of the racing bicycle hub designed to receive a nut for fastening a wheel. Racing bicycle hub according to claim 2, wherein the thread (12) is at least partially hardened. Racing bicycle hub according to claim 2 or 3, wherein the tips (16) of the thread (12) are laser-hardened and wherein the flanks (18) of the thread (12) transition from the laser-hardened tips (16) into a non-hardened area in the thread (20). Racing bicycle hub according to one of claims 2 to 4, wherein a first turn (16-1) of the thread (12) is laser hardened. Racing bicycle hub according to one of the preceding claims, wherein the hardening depth of the at least one non-functional, laser-hardened surface (12) extends to a maximum of 2 mm, in particular to a maximum of 1.5 mm. Racing bicycle hub according to one of the preceding claims, wherein the hardness of the at least one non-functional, laser-hardened surface (12) is greater than 45 HRC, in particular greater than 50 HRC. Racing bicycle hub according to one of the preceding claims, wherein the raceway (4) has an induction-hardened raceway surface. Racing bicycle hub according to claim 8, wherein the racing bicycle hub (1) has a soft zone between the induction-hardened raceway surface (4) and the at least one non-functional, laser-hardened surface (12).

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