Brake disc, method for machining a brake disc, and motor vehicle
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- BAYERISCHE MOTOREN WERKE AG
- Filing Date
- 2026-01-13
- Publication Date
- 2026-07-30
Smart Images
Figure DE2026100027_30072026_PF_FP_ABST
Abstract
Description
[0001] 24-3636
[0002] brake disc, method for machining a brake disc and motor vehicle
[0003] The invention relates to a brake disc for a motor vehicle, a method for machining a brake disc, in particular a brake disc for a motor vehicle, and a motor vehicle with a brake disc.
[0004] From DE 102008042818 A1, a brake disc is known, comprising a friction ring and a disc hub connected to the friction ring via connecting elements. The connecting elements are pins.
[0005] Furthermore, EP 2337967 B1 discloses a ventilated brake disc with a friction ring consisting of at least two discs separated by webs and a support element. Several connecting elements are attached to the circumference of the support element and project into support webs formed on the friction ring. These connecting elements are pins.
[0006] Furthermore, WO 2010 / 124890 A1 discloses a brake disc with a friction ring and a disc hub connected to the friction ring via connecting links. These connecting links are also pins.
[0007] The object of the present invention is to ensure thermal expansion of a friction ring attached to a brake disc hub via connecting elements relative to the brake disc hub. 24-3636
[0008] 2
[0009] This problem is solved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.
[0010] The invention relates to a brake disc for a motor vehicle, in particular a car, and especially a passenger car. The brake disc can be part of a braking system of the motor vehicle. The braking system is a technical device of the motor vehicle designed to decelerate the motor vehicle and thus reduce its speed, in particular until the motor vehicle comes to a standstill. In addition to the brake disc, the braking system can include at least one brake pad, which is to be applied to a friction surface of the brake disc for braking the motor vehicle. The friction surface is thus designed to be brought into contact with the brake pad when the brake disc is used as intended on the motor vehicle for deceleration.To brake the motor vehicle, at least one brake pad is pressed against the friction surface of the brake disc, thereby braking the motor vehicle due to the resulting friction between the at least one brake pad and the brake disc. In particular, the brake disc has a friction surface on each of its axially opposite end faces, each of which is designed to be brought into contact with at least one brake pad for braking the motor vehicle.
[0011] The brake disc includes a friction ring, which provides a friction surface on each end face. The friction ring has a basic shape that is at least substantially annular. The friction ring comprises a base body and a coating arranged on the respective end faces of the base body. This coating is, in particular, a hard coating. (With other 24-3636)
[0012] 3
[0013] In other words, the friction ring has the coating on at least its respective end faces. The friction surfaces are provided by the coating. In particular, the friction surfaces, like the friction ring, have an annular shape. Here, the friction surfaces are each bounded radially to a central axis of the brake disc by a friction surface edge.
[0014] The brake disc further comprises a brake disc hub, which is radially enclosed by the friction ring. This means that the brake disc hub is located within the central opening of the annular friction ring. The brake disc hub is positioned such that its central axis coincides with the central axis of the brake disc. The brake disc is rotationally symmetrical about its central axis. This brake disc hub is, in particular, a cast aluminum component. The brake disc hub can therefore be cast from a material containing aluminum.
[0015] Furthermore, the brake disc comprises several pin-shaped connecting elements, each of which is inserted at one end through a corresponding insertion hole in the friction ring and at the other end is arranged in a corresponding recess in the brake disc hub. The respective insertion holes of the friction ring can each extend radially along the brake disc. In particular, the friction ring has several insertion holes arranged at regular intervals around the central axis of the brake disc. This allows the insertion holes to radiate outwards from the central axis of the brake disc in a star-shaped pattern within the friction ring. A connecting element is inserted into each insertion hole of the friction ring. The other end of each connecting element can be encased in the brake disc hub.In other words, the brake disc could have been manufactured by inserting a connecting element into each of the respective insertion holes of the friction ring and then casting the brake disc hub around the other ends of the connecting elements, which are arranged facing the central axis of the brake disc. The friction ring is thus connected to the brake disc hub via these connecting elements. The connecting elements therefore allow for particularly simple and secure fixing of the friction ring in the axial direction of the brake disc relative to the brake disc hub, as well as particularly simple and secure centering of the brake disc hub within the central opening of the 24-3636.
[0016] 4
[0017] Friction ring. The friction ring is designed to slide on the connecting elements, allowing it to expand along the central axis of the brake disc when the friction ring expands thermally. This sliding movement of the friction ring on the connecting elements compensates for thermal expansion of the friction ring relative to the brake disc hub. Consequently, as the friction ring expands, an edge of the friction ring that circumferentially defines the insertion opening moves radially towards the brake disc relative to the connecting element inserted into the corresponding insertion hole, in the direction of the brake disc hub. The lengths of the respective connecting elements swept by the edges of the friction ring that define the corresponding insertion openings during thermal expansion are the respective critical lengths of the connecting elements.In other words, the area of the connecting element swept radially along the brake disc by the edge that limits the insertion openings is the critical length range of this connecting element during the thermal expansion of the friction ring.
[0018] If the coating is applied to the base of the friction ring after the connecting elements have been inserted into their respective insertion holes, coating material can accumulate on the connecting elements due to overspray. If the coating material accumulates on one of the connecting elements in the critical length range, the thermal expansion of the friction ring can be blocked if the coating material protrudes so far beyond the connecting element in this critical length range that the friction ring, when expanding due to thermal expansion, abuts this coating material. This impact can prevent the circumferential edge of the friction ring from moving further radially beyond the critical length range of the connecting element towards the central axis of the brake disc.To ensure the thermal expansion of the friction ring, it is therefore necessary to prevent coating material accumulating in the critical length range of at least one of the connecting elements from blocking the thermal expansion of the friction ring. This can be achieved by providing a masking system in the coating system for applying the coating material to the base body, whereby the masking prevents the coating material from accumulating in the respective critical areas.
[0019] 5
[0020] Depositing coating material in critical length areas on the connecting elements could place high technical demands on the coating system. Therefore, the brake disc is designed to be modified in such a way as to effectively prevent the thermal expansion of the friction ring from being blocked by coating material located in the critical length area of at least one connecting element. In other words, a design feature of the brake disc is implemented to prevent coating material from depositing on the respective connecting elements in the critical length areas in such a way that this coating material protrudes axially to such an extent that it collides with the edge of the friction ring that defines the insertion opening when the friction ring expands due to heat.
[0021] The following section explains various design measures that can be used individually or in combination to achieve the aforementioned effect. The first design measure involves ensuring that the connecting element is covered on its sides opposite each other in the axial direction of the brake disc in the critical length range. This means that the connecting element in the critical length range is covered and thus masked by a component of the brake disc itself. The masking is therefore part of the brake disc. This eliminates the need for time-consuming, precise alignment of a separate masking element relative to the brake disc to avoid applying coating material to the respective critical length ranges of the connecting elements.Instead, by covering the respective critical length ranges of the connecting elements with a component of the brake disc itself, a precise masking of these critical length ranges can be achieved.
[0022] The second design measure provides that, in the critical length range of the respective connecting element, on both sides opposite each other in the axial direction of the brake disc, the axially extending distance between the connecting element and the edge circumferentially delimiting the insertion opening is chosen to be greater than the axially extending thickness of the respective coating, which is arranged on the same side of the connecting element as the distance in question. In other words, 24-3636
[0023] 6
[0024] The brake disc is designed such that, in the critical length region of the connecting element, a gap exists on both axially opposite sides of the connecting element, bordering the edge defining the insertion opening into which this connecting element is inserted. The axial extent of the gap is greater than the thickness of the coating located on the same side of the connecting element, relative to the axial direction of the brake disc, as the gap in question.This ensures that, even if coating material comes into contact with the connecting element in the critical length range, the edge of the friction ring that defines the insertion opening does not abut this coating material, even if the coating material in the critical length range has the same thickness as on the end face of the base body, due to this set distance. This occurs when the friction ring expands towards the central axis of the brake disc as a result of heating [WFM5Bi] and thus the edge defining the insertion opening moves radially over the critical length range of the connecting element. At temperatures below the manufacturing temperature of the friction ring, the friction ring may contract.The aforementioned third constructive measure thus makes it possible to ensure that, despite the deposition of coating material in the critical length area of the connecting element, the thermal expansion of the friction ring relative to the connecting element is possible by avoiding a collision between the edge limiting the insertion opening and coating material that could be deposited on the critical length area of the connecting element.
[0025] In a possible further development of the invention, the insertion hole has a centering area and a spacer area. In the centering area, which extends radially outwards from the spacer area along the brake disc, the wall of the friction ring circumferentially delimits the insertion hole rests circumferentially on the outside of the connecting element inserted into this insertion hole. In the spacer area, the insertion hole has a greater extent, at least in the axial direction of the brake disc, than in the centering area. In the centering area, the friction ring rests completely circumferentially against the connecting element, allowing the friction ring to be centered relative to the brake disc hub via this contact with the centering area. In the spacer area, the insertion hole extends at least in the axial direction of the brake disc.
[0026] 7
[0027] The wall of the friction ring, bounding opposite sides, increases the distance to the connecting element to ensure that, in the event of thermal expansion of the ring element, the ring element can move relative to the connecting element in such a way that the critical length region of the connecting element can be moved, at least partially, and in particular completely, into the space region of the friction ring, without creating a risk of collision between coating material deposited on the connecting element in the critical length region and the edge of the friction ring that defines the insertion opening or with the wall of the friction ring that defines the space region. The insertion hole is thus widened with its opening facing the central axis of the brake disc due to the design, which includes the centering region and the space region.This enlarged design of the insertion hole ensures that even if the edge of the friction ring, which defines the insertion opening, moves towards the central axis of the brake disc due to thermal expansion, this edge does not collide with coating material that has accumulated on the connecting element, for example, due to overspray, and thus does not impede the thermal expansion of the friction ring. The design of the insertion hole with its centering area and spacer ensures that the axial distance between the connecting element and the edge surrounding the insertion opening is greater than the axial thickness of the respective coating.It is therefore provided that the axial distance of the spacer area to the respective nearest sides of the connecting element is at least as large as the axial thickness of the respective coating located on the same side of the connecting element. Furthermore, it may be provided that the radial distance area of the spacer area is at least as long as the critical length of the connecting element.
[0028] In this context, it may be provided, in particular, that the spacing range is provided by a radial recess. The recess may, for example, be designed as a radial conical countersink, a radial flat countersink, or a blind hole recess in the friction ring. In particular, it is provided that a separate recess, in particular a conical countersink or 24-3636, is provided for each insertion opening.
[0029] 8
[0030] The countersink is provided for. This minimizes the removal of material from the friction ring by incorporating the respective countersinks. This ensures exceptional stability of the friction ring.
[0031] In a further possible embodiment of the invention, the connecting element has a cross-section that is tapered at least with respect to the axial direction of the brake disc in the critical length region. This tapering can extend over the entire critical length region or be provided only in a part thereof.This at least partial tapering of the connecting element, at least with respect to its axial extension along the brake disc, results in the following: in the critical length range, the axial distance between the connecting element and the edge circumferentially bounding the insertion opening on both sides of the connecting element opposite each other in the axial direction along the brake disc is greater than the axial thickness of the respective coating located on the same side of the connecting element as the distance in question. In other words, the tapering of the connecting element can be chosen to be so deep that it is deeper in the axial direction along the brake disc than the thickness of the coating located on the same side of the connecting element as the tapering in question.This ensures that all overspray can be contained within the tapered section, without any coating material protruding axially from the brake disc beyond a non-tapered area of the connecting element. It is possible that this required distance, at least in the axial direction, between the connecting element in the critical length range and the edge defining the insertion opening can be provided at least partially by the tapered section and at least partially by the insertion hole's clearance area, with the clearance area having a greater axial extent than the centering area.
[0032] Designing the connecting element with a tapered cross-section in the critical length range makes it possible to avoid collisions between the edge limiting the insertion opening and the coating material on the connecting element, thereby ensuring particularly high stability of the friction ring.24-3636
[0033] 9
[0034] The depth of the taper is chosen particularly depending on the coating thickness or the expected overspray.
[0035] In a further possible embodiment of the invention, the connecting element is provided that, in the critical length region, its sides opposite each other in the axial direction of the brake disc are covered outwards by a radial projection of the friction ring and / or by a radial projection of the brake disc hub. It is particularly provided that the connecting element is covered outwards in the axial direction towards the friction surfaces along its entire critical length region and is thereby masked. This covering can be provided by the radial projection of the friction ring and / or by the radial projection of the brake disc hub.This results in the shielding of at least a partial area, in particular the entire critical length of the connecting element in the axial direction of the brake disc to the outside. This effectively prevents coating material from adhering to the connecting element in the critical length due to overspray, for example. The friction ring can be provided with a radial projection on its side facing the central axis of the brake disc, featuring at least one circumferential cold-running collar extending radially towards the central axis. This cold-running collar can also stabilize the friction ring during operation, minimizing the risk of it folding over or becoming misaligned.
[0036] Alternatively or additionally, for at least one of the connecting elements, and in particular for each connecting element, a separate radial extension of the friction ring can be provided as a projection enclosing the respective connecting element, which projects from the friction ring towards the brake disc hub. Within the respective radial extension is the insertion hole, which opens into the surrounding area on a side of the radial extension facing the brake disc hub via the insertion opening towards the brake disc hub.
[0037] In this context, it may be provided that the radial projection of the friction ring extends in a ring-like fashion around the central axis of the brake disc. Here, it is possible that the connecting element to the two parts is axially oriented.24-3636
[0038] 10
[0039] On the opposite side of the brake disc, each side is covered by an annular projection of the friction ring. This annular projection extends radially towards the brake disc hub. These annular projections thus cover all critical lengths of all connecting elements of the brake disc in the axial direction outwards, protecting them from accumulating coating material. Together, these annular projections define an annular groove that runs around the brake disc hub and is located on the side of the friction ring facing the brake disc hub. The respective insertion holes open into this annular groove.This means that the respective insertion openings are arranged in the base of the annular groove. Due to the arrangement of the insertion openings in the annular groove, the critical lengths of the connecting elements inserted into their respective holes are covered by the annular projections in the axial direction of the brake disc and thus protected from the accumulation of coating material. Consequently, the risk of collision between the edge surrounding each insertion opening and coating material that has accumulated in the critical length range of a connecting element is minimized, thus ensuring the proper thermal expansion of the friction ring.
[0040] In an alternative embodiment of the invention, the base body comprises gray cast iron and / or the coating comprises at least one hard material, in particular corundum and / or a carbide. The friction ring thus comprises the gray cast iron base body, which is coated with a layer system comprising at least one layer in the form of the coating. The base body can therefore comprise a gray cast iron alloy, in particular one of the alloys GG15 to GG35. Gray cast iron has a high melting point as well as particularly good heat storage and damping properties. Furthermore, gray cast iron is particularly easy to cast and machine. The layer system with which the base body is coated comprises at least one friction layer, which includes the at least one hard material. 24-3636
[0041] 11
[0042] The friction layer seals the friction ring on the outside and, when the brake disc is used as intended, can be brought into contact with the at least one brake pad for braking the vehicle. Hard materials are materials characterized by particularly high hardness. In particular, the hard material is an intermetallic phase, such as a metal carbide, or individual particles, as in the case of a ceramic. Because the friction layer contains at least one hard material, it exhibits particularly low wear and, consequently, a particularly long service life. Carbides are binary chemical compounds consisting of an element and carbon. In particular, the carbide is a metallic carbide, such as tungsten carbide, titanium carbide, iron carbide, silicon carbide, or nickel carbide.These metal carbides exhibit exceptionally high hardness, resulting in a particularly robust and wear-resistant friction layer. Corundum is a relatively common material belonging to the mineral class of oxides and hydroxides and possesses very high hardness. Aluminum oxide is the oxygen compound of the chemical element aluminum and is also known as electrocorundum in technical fields.
[0043] The invention further relates to a method for machining a brake disc, as already described in connection with the brake disc according to the invention. In this method, the coating is applied to the respective end faces of the base body while the respective connecting elements are inserted into their corresponding insertion holes. It is possible for the connecting elements to be pre-inserted into the insertion holes to ensure that the friction ring can be positioned with particular precision within a coating system during the application of the coating to the base body.Alternatively, it may be possible to refurbish a previously used brake disc whose coating applied to the base body is already worn, and consequently, to coat the respective end faces of the base body with coating material while the respective connecting elements are inserted into their corresponding insertion holes. The described method thus allows the base body to be coated with the respective end faces while the connecting elements are arranged in their corresponding insertion holes, 24-3636.
[0044] 12
[0045] where the risk of limiting or hindering the thermal expansion of the friction ring due to a collision between the edge of the friction ring that limits the respective insertion opening and coating material that has accumulated on the respective associated connecting element can be kept particularly low.
[0046] The invention further relates to a motor vehicle with a brake disc as already described in connection with the brake disc according to the invention. The brake disc is, in particular, part of a braking system of the motor vehicle. It can be provided that a brake disc is provided for at least two wheels of the motor vehicle, in particular for each wheel of the motor vehicle. Furthermore, the motor vehicle can have at least one, in particular at least two, brake pads for each brake disc, wherein these two brake pads can be applied to sides of the brake disc that are opposite each other in the axial direction of the brake disc for braking, in particular to the respective friction surfaces. The use of the described brake disc with its particularly long service life in the motor vehicle means that the respective brake discs in the motor vehicle only need to be replaced very rarely.Furthermore, the aforementioned brake disc allows for the possibility that, should wear of a coating on the brake disc occur, the brake disc can subsequently be provided with a new coating, whereby the risk of blockage due to thermal expansion of the friction ring is particularly low with this recoated brake disc.
[0047] Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.
[0048] The drawing shows in:
[0049] Fig. 1 shows a partial schematic sectional view of a brake disc for a motor vehicle in a first embodiment; 24-3636
[0050] 13
[0051] Fig. 2 shows a partial schematic sectional view of the cut brake disc in a second embodiment;
[0052] Fig. 3 shows a partial schematic sectional view of the cut brake disc in a third embodiment; and
[0053] Fig. 4 shows a partial schematic sectional view of the cut brake disc in a fourth embodiment. [WFM5B2]
[0054] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.
[0055] Figures 1 to 4 show schematic, partial sectional views of a brake disc 10 in different embodiments. The brake disc 10 is intended for use in a motor vehicle, in particular a car, especially a passenger car. The brake disc 10 is a so-called pin brake disc. The brake disc 10 comprises a friction ring 12 with a plurality of insertion holes 14. A pin-shaped connecting element 16 is inserted into each of these holes. The respective pin-shaped connecting elements 16 extend in the radial direction R of the brake disc 10. The radial direction R is perpendicular to an axial direction A of the brake disc 10. The axial direction A of the brake disc 10 runs parallel to a central axis 18 of the brake disc 10.When the axial direction A or the radial direction R is mentioned below, these statements always refer to the axial direction A of the brake disc 10 or to the radial direction R of the brake disc 10.
[0056] The friction ring 12 is ring-shaped, whereby the friction ring 12 encloses a volume arranged centrally with respect to the radial direction R of the brake disc 10. A brake disc hub 20 is arranged within this volume. This brake disc hub 20 is, in this case, an aluminum die-cast component, which is cast around the respective free ends of the connecting elements 16 inserted into the respective corresponding insertion holes 14. This means that the respective pin-shaped connecting elements 16 are inserted at one end into a 24-3636
[0057] 14
[0058] The connecting element 16 is inserted into the corresponding insertion hole 14 of the friction ring 12 and cast into the brake disc hub 20 at the other end. The insertion hole 14 opens into the surrounding area through an insertion opening 22, through which the connecting element 16 is inserted into the respective insertion hole 14. The insertion opening 22 is located on one side of the friction ring 12 facing radially towards the central axis 18.
[0059] The friction ring 12 comprises a base body 24, which is made of gray cast iron. Additionally, the friction ring 12 has a coating 26 on each of the end faces of the base body 24 that are opposite each other in the axial direction A of the brake disc 10. The respective coatings 26 provide a friction surface 28 on each end face of the friction ring 12. The respective friction surfaces 28 are thus provided by the coating 26. Each of the friction surfaces 28 is bounded radially to the central axis 18 of the brake disc 10 by a friction surface edge 30. It is provided that the base body 24 of the friction ring 12 is provided with the coating 26 on its respective end faces, while the connecting elements 16 are inserted into the respective insertion holes 14 of the friction ring 12.
[0060] It is provided that the coating 26 comprises at least one hard material, in particular a corundum and / or a carbide. Furthermore, it is provided that the coating 26 is applied to the base body 24 by a coating process involving powder deposition, in particular by laser cladding, cold gas spraying, or high-velocity flame spraying.
[0061] In particular, it is provided that the coating material is applied to the surfaces of the base body 24 to be coated by directing a jet, especially a powder jet, flowing at least substantially in the axial direction A of the brake disc 10 and encompassing the coating material. It is essential to prevent overspray of the coating material from settling on the respective connecting elements 16 in a critical length range 32. In spray applications, overspray refers to the portion of the sprayed coating material that is not applied to the surface of the base body 24 to be coated, but escapes into the environment as spray mist. 24-3636
[0062] 15
[0063] The friction ring 12 is designed to slide on the respective connecting elements 16. This allows, in the event of thermal expansion of the friction ring 12, an edge 34 of the friction ring 12, which circumferentially defines the insertion opening 22, to move radially R of the brake disc 10 relative to the connecting element 16 inserted into the associated insertion hole 14, towards the brake disc hub 20, over the critical length 32 of the connecting element 16. In this case, the critical length 32 of the respective connecting elements 16 extends radially R towards the brake disc hub 20 from a region of the respective connecting element 16 which is covered outwards by the edge 34 in the axial direction A of the brake disc 10.The radial length of the critical length range 32 corresponds to the radial length R of the connecting element over which the edge 34 moves maximally during the thermal expansion of the friction ring 12.
[0064] One way to protect the respective critical length regions 32 of the connecting elements 16 from the deposition of coating material is to provide at least one masking element during the coating of the base body 24, which is designed separately from the brake disc 10. This masking element must be precisely aligned relative to the brake disc 10 to reliably protect the critical length regions 32 of the connecting elements 16 from coating material. In this case, a design feature on the brake disc 10 is intended to significantly reduce the risk of a collision between the edge 34 defining the insertion opening 22 and coating material in the critical length region 32 of the connecting element 16 inserted into this insertion opening 22. The different embodiments of the brake disc 10 shown in Figures 1 to 4 illustrate various possible design features of the brake disc 10.
[0065] In the embodiment shown in Fig. 1, a groove 40 is provided on the side of the friction ring 12 facing the brake disc pot 20, which runs around the brake disc pot 20 and in which the respective insertion openings 22 are arranged.
[0066] In the embodiment shown in Fig. 2, it is provided that the connecting element 16 in the critical length range 32 is each supported on its sides opposite each other in the axial direction A of the brake disc 10 by a radial 24-3636
[0067] 16
[0068] The projection 44 of the friction ring 12 is covered on the outside. These radial projections 44 of the friction ring 12 thus mask the critical length region 32 on the sides opposite each other in the axial direction A. Here, with respect to the axial direction A, the projections 44 are each arranged between the connecting element 16 and the friction surfaces 28. The respective projections 44 can be provided by a cold-running collar.
[0069] Figure 3 shows a combination of two design measures, each of which can also be implemented separately. The first design measure is a modification of the friction ring 12 in Figure 3 such that the edge 34 defining the insertion opening 22 is offset in the axial direction A of the brake disc 10 relative to the outer surface of the connecting element 16 in the critical length region 32. In other words, there is a distance in the axial direction A between the critical length region 32 of the respective connecting element 16 and the edge 34. In particular, this distance in the axial direction A can be greater on each of the sides of the connecting element 16 opposite each other in the axial direction A of the brake disc 10 than the coating thickness in the axial direction A of the coating applied to the same side of the connecting element 16.This distance between the connecting element 16 in the critical length region 32 and the edge 34 ensures that, even if coating material is deposited in the critical length region 32 of the connecting element 16 to the full height of the coating thickness, the edge 34 can move along the radial direction R relative to the connecting element 16, particularly over the critical length region 32, without the edge 34 colliding with the coating material deposited on the connecting element 16 in the critical length region 32 and thus causing it to bind. Consequently, it is ensured that the friction ring 12 can expand radially R towards the brake disc hub 20 as a result of heat generation in the friction ring 12.
[0070] In the embodiment shown in Fig. 3, this distance is achieved by providing a radially extending recess or indentation 42 in the side of the friction ring 12 facing the brake disc hub 20. By providing this recess 42, the respective insertion holes 14 each have a centering area 36 and a spacing area 38. The centering area 36 encloses in 24-3636
[0071] 17
[0072] In the radial direction R, the friction ring 12 abuts the spacer area 38 on the side facing away from the brake disc hub 20. In the centering area 36, a wall of the friction ring 12, which circumferentially delimits the insertion hole 14, rests against the outer surface of the connecting element 16 over its entire circumference. In the spacer area 38, at least in the axial direction, and in particular circumferentially around the connecting element 16, there is a gap between the wall of the friction ring 12, which delimits the friction ring 12 in the spacer area 38, and the connecting element 16. It is provided that the spacer area 38 has a greater extent than the centering area 36, at least in the axial direction A of the brake disc 10. In the embodiment shown in Fig. 3, the spacer area 38 is provided by the recess 42, in this case a conical recess, which circumferentially encloses the connecting element 16.
[0073] In the embodiment shown in Fig. 3, a second design feature is that the respective connecting element 16 is covered on its sides opposite each other in the axial direction A of the brake disc 10 by a radial projection 46 of the brake disc hub 20. It is particularly provided that the connecting element 16 is covered axially outwards by the radial projection 46 of the brake disc hub 20, at least partially in the critical length range 32 in the axial direction A of the brake disc 10. Furthermore, it is particularly provided in this case that the respective radial projections 44, 46 are arranged circumferentially around the central axis 18 on the friction ring 12 and on the brake disc hub 20, respectively. The projections 44, 46 can be ridges.
[0074] In the embodiment shown in Fig. 4, the connecting element 16 has a cross-section that is tapered at least with respect to the axial direction A of the brake disc 10 in the critical length region 32. This means that the connecting element 16 has a tapering 48 of the cross-section at least with respect to the axial direction A in the critical length region 32. This tapering 48 ensures that, in the critical length region 32, on both sides of the connecting element 16 opposite each other in the axial direction A of the brake disc 10, the distance in the axial direction A between the connecting element 16 and the edge 34 circumferentially bounding the insertion opening 22 is greater than the thickness of the 24-3636 in the axial direction A.
[0075] 18
[0076] respective coating 26, which is arranged on the same side of the connecting element 16 as the distance under consideration.
[0077] In the embodiment shown in Fig. 4, the cross-sectional reduction 48 is achieved by a constriction of the connecting element 16. This constriction ensures that, even when coating material is applied in the critical length range 32, the friction ring 12 does not slide radially R along the connecting element 16 over this critical length range 32, nor is it hindered or prevented by the coating material. The depth of the constriction extending in the axial direction A is approximately equal to the thickness of the coating 26.In particular, the taper 48 is selected such that the axially extending distance A between the connecting element 16 and the edge 34 circumferentially bounding the insertion opening 22 is greater in the critical length range 32 than the axially extending thickness A of the respective coating 26, which is arranged on the same side of the connecting element 16 as the distance under consideration. In particular, this axially extending distance A may be between 300 micrometers and 500 micrometers.
[0078] The described invention is based on the understanding that, in order to comply with required brake emission standards, it is advantageous to provide the base body 24 with the coating 26 comprising hard materials. The base body 24 can be coated with a two-layer system. In this system, at least the outermost layer comprises at least one hard material. Even the wear-resistant, hard-material-reinforced layer can be subject to a certain degree of abrasive wear during intended use in a motor vehicle. In the case of the pin-type brake disc shown in the figures, it is necessary during coating to protect the pin-shaped connecting elements 16 from overspray of the coating material. Overspray occurs with any type of coating using powder application. It is essential to prevent the thermal expansion and contraction of the friction ring 12 from being blocked by coating material applied to the respective connecting elements 16.
[0079] Overall, the invention shows how a pin brake disc can be coated without using a separate masking system for the brake disc 10.4-3636
[0080] 19
[0081] Reference symbol list
[0082] 10 brake disc
[0083] 12 friction ring
[0084] 14 insertion holes
[0085] 16 Connecting element
[0086] 18 Central axis
[0087] 20 brake disc hub
[0088] 22 Insertion opening
[0089] 24 basic shapes
[0090] 26 Coating
[0091] 28 friction surface
[0092] 30 friction surface edge
[0093] 32 critical length range
[0094] 34 edge limiting the insertion opening
[0095] 36 Centering area
[0096] 38 Distance range
[0097] 40 Nut
[0098] 42 depression
[0099] 44 lead
[0100] 46 lead
[0101] 48 Rejuvenation
[0102] A axial direction
[0103] R radial direction
Claims
24-3636 20 Patent claims 1. Brake disc (10) for a motor vehicle, with a friction ring (12) providing a friction surface (28) on each end face, which comprises a base body (24) and a coating (26) arranged on each end face of the base body (24), wherein the friction surfaces (28) are each provided by the coating (26) and are each radially bounded to a central axis (18) of the brake disc (10) by a friction surface edge (30), a brake disc hub (20) which is radially enclosed by the friction ring (12), several pin-shaped connecting elements (16), each of which is inserted at one end through an insertion opening (22) into a respective insertion hole (14) of the friction ring (12), which extends radially (R) with its longitudinal direction, and is arranged at the other end in a respective recess of the brake disc hub (20), wherein the friction ring (12) is slidably seated on the connecting elements (16), whereby, in the event of thermal expansion of the friction ring (12), an edge (34) circumferentially bounding the insertion opening (22) moves in the radial direction (R) of the brake disc (10) relative to the connecting element (16) inserted into the associated insertion hole (14) in the direction of the brake disc hub (20) over a critical length region (32) of the connecting element (16), wherein the connecting element (16) in the critical length range (32) is covered outwards on its sides opposite each other in the axial direction (A) of the brake disc (10), and / or In the critical length region (32), on both sides of the connecting element (16) opposite each other in the axial direction (A) of the brake disc (10), the axially extending distance (A) between the connecting element (16) and the edge (34) circumferentially bounding the insertion opening (22) is greater than the axially extending thickness (A) of the respective coating (26) which is arranged on the same side of the connecting element (16) as the considered distance.24-3636 21 2. Brake disc (10) according to claim 1, characterized by the fact that The insertion hole (14) has a centering area (36) and a spacer area (38), wherein in the centering area (36), which extends outwards in the radial direction (R) of the brake disc (10) to the spacer area (38), the wall of the friction ring (12) circumferentially delimiting the insertion hole (14) bears circumferentially on the outside of the connecting element (16) inserted into this insertion hole (14), and wherein in the spacer area (38) the insertion hole (14) has a greater extent at least in the axial direction (A) of the brake disc (10) than in the centering area (36).
3. Brake disc (10) according to claim 2, characterized by the fact that The spacing range (38) is provided by a radial recess.
4. Brake disc (10) according to one of the preceding claims, characterized by the fact that the connecting element (16) in the critical length region (32) has a cross-section (48) that is tapered at least with respect to the axial direction (A) of the brake disc (10).
5. Brake disc (10) according to one of the preceding claims, characterized by the fact that the connecting element (16) in the critical length range (32) is covered on its sides opposite each other in the axial direction (A) of the brake disc (10) by a radial projection of the friction ring (12) and / or by a radial projection of the brake disc hub (20) to the outside.
6. Brake disc (10) according to claim 5, characterized by the fact that the radial projection of the friction ring (12) extends in a ring shape around the central axis (18) of the brake disc (10).
7. Brake disc (10) according to one of the preceding claims, characterized in that the base body (24) comprises grey cast iron and / or the coating (26) comprises at least one hard material, in particular a corundum and / or a carbide.
8. Method for machining a brake disc (10) according to one of the preceding claims, in which the coating (26) is applied to the respective end faces of the base body (24), while the respective connecting elements (16) are inserted into the respective associated insertion holes (14).
9. Motor vehicle with a brake disc (10) according to one of claims 1 to 7.