Brake disc manufacturing method
By prefabricating brake discs with a radial gradient to counteract thermal deformation, the method addresses shape distortion and uneven wear protection, achieving uniform thickness and improved manufacturing efficiency.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- BRIDEN GAME M BE HER
- Filing Date
- 2025-10-14
- Publication Date
- 2026-04-28
AI Technical Summary
Existing brake disc manufacturing methods using laser metal deposition cause shape distortion and uneven wear protection layer thickness due to thermal stress, requiring additional preheating steps that increase cost and risk oxidation, and result in uneven wear and increased particulate emissions.
A method that prefabricates the substrate with a radial gradient to compensate for thermal deformation during wear protection layer formation, ensuring uniform thickness and high adhesion, eliminating the need for preheating and reducing distortion, thereby improving manufacturing efficiency and reducing costs.
The method achieves a brake disc with uniform wear protection layer thickness, high adhesion, and reduced particulate emissions by compensating for thermal stress through prefabrication, ensuring high precision and cost-effectiveness.
Smart Images
Figure 2026071181000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a brake disc according to claim 1.
Background Art
[0002] Brake discs, particularly those made of vermicular graphite cast iron, are known from the prior art. These brake discs have a substrate with a friction ring, and the friction ring has two opposing annular friction surfaces. In order to improve the wear characteristics of the substrate made of vermicular graphite cast iron, it is known to provide a wear protection layer on the two friction surfaces by laser metal deposition, which ensures a high mileage of the manufactured brake disc. In this process, the outer surface of each friction surface to be coated is melted by a laser beam, and at the same time, at least one coating powder is supplied onto the molten friction surface. This coating powder is preferably at least partially melted by the laser beam before reaching the molten friction surface, thereby causing a material bond to occur between the friction surface and the coating powder, and a wear protection layer is formed. As a result of this material bond, the wear protection layer formed by laser metal deposition has high coating adhesion and peeling resistance. Corresponding brake discs are described, for example, in European Patent Application Publication No. 3034902, German Patent Application Publication No. 102019207291, and German Patent Application Publication No. 102021104237.
[0003] A drawback of laser metal deposition is the change in brake disc shape due to high thermal input. During laser metal deposition, thermal stress causes the friction ring of the substrate to deform in the direction of the outer or inner friction surface of the brake disc, depending on the coating order of the friction surface. Furthermore, after laser metal deposition, the wear protection layer has a high surface roughness of up to 100 μm. Therefore, in the next process, such as grinding, the wear protection layer is smoothed so that the friction surface is perpendicular to the rotation axis of the brake disc. The distortion of the friction ring after laser metal deposition results in the drawback that the thickness of the wear protection layer varies greatly in the radial direction during the smoothing process. Due to distortion correction during smoothing, the amount of wear protection layer removed differs greatly in the radial direction.
[0004] To reduce substrate distortion, German Patent Application Publication No. 102020112100 proposes preheating the substrate to a temperature of 100°C to 700°C before laser metal deposition. However, the disadvantage of preheating a gray cast iron substrate is that it requires an additional process step, thereby requiring additional energy, cost, and time. Furthermore, preheating can cause oxidation of the two friction surfaces of the friction ring, which impairs the adhesion between the friction ring and the wear protection layer. [Overview of the Initiative]
[0005] The object of the present invention is to provide a brake disc and / or a method for manufacturing the same, in which a wear protection layer is provided on the friction surface with a uniform coating thickness, and this wear protection layer has high coating adhesion and peel resistance. The manufacturing process should be highly reliable and cost-effective, thereby reducing the manufacturing cost of the brake disc.
[0006] The features of the invention are described in claim 1. The improved forms are the subject matter of claims 2 to 11.
[0007] The present invention relates to a method for manufacturing a brake disc, particularly a coated brake disc, comprising (a) prefabricating a substrate having a hub fixing portion and a friction ring made of metal, particularly gray cast iron, wherein the hub fixing portion has an annular hub contact surface and the friction ring has two opposing annular friction surfaces extending around the axis of rotation of the substrate, by casting the substrate from metal and optionally removing material from the friction surface region and / or the hub contact surface region after casting, such that the annular friction surfaces have a radial gradient with respect to the hub contact surface. Subsequently, (b) a wear protection layer is formed on one or both of the friction surfaces such that the thermally induced stress in this step deforms the annular friction surfaces in such a way that the absolute value of the radial gradient is reduced to a lower absolute value of the residual radial gradient.
[0008] The advantage of this method is that it eliminates the need for additional steps such as known preheating processes. Therefore, this method is safe, fast, and cost-effective. Oxidation of the substrate and reduction in adhesion of the wear protection layer, which occur during preheating, are eliminated. The problem of distortion during laser metal deposition can also be effectively solved. Because a lower residual gradient is achieved in the radial direction, the brake disc already has high-precision dimensions after the wear protection layer is formed. Material removal and finishing of the friction surface can be performed more uniformly, so a uniform thickness of the wear protection layer is maintained. By defining the absolute value of the gradient, the process also includes cases where the friction surface deforms to such an extent that the sign of the gradient changes.
[0009] Technically, the radial gradient is optionally formed by material removal in the friction surface region or by additional or alternative material removal in the contact surface region.
[0010] Detailed improvements to the method result in a configuration where, after the formation of the wear protection layer, the residual radial gradient is substantially or completely 0° (particularly with respect to the hub contact surface), so that the friction surface is oriented at least substantially or completely perpendicular to the axis of rotation, particularly in the brake disc mounting state. This eliminates the need for finishing work to correct the shape of the friction surface. Finishing work is limited at least substantially to adjusting the surface roughness.
[0011] Specifically, the friction surfaces are configured to have a ring width with an inner diameter and an outer diameter, and during the prefabrication of the base, a radial gradient is formed on the friction surfaces along an axis perpendicular to the hub contact surface such that the inner diameter is offset relative to the outer diameter, with the absolute value of this offset being between 10 μm and 90 μm, preferably between 30 μm and 70 μm. The radial gradient thus formed is generally sufficient to compensate for thermal deformation during the formation of the wear protection layer.
[0012] Furthermore, according to this method, the friction surfaces may be configured to have a ring width with an inner diameter and an outer diameter, and after the formation of the wear protection layer, the residual gradient in the radial direction is formed such that the inner diameter is offset relative to the outer diameter in the axial direction perpendicular to the hub contact surface, and the absolute value of this offset is less than 50 μm, preferably less than 30 μm. With this maximum offset value, during finishing, it is necessary to locally remove the wear protection layer at a value below this to obtain a friction surface perpendicular to the rotation axis.
[0013] In certain improved forms of this method, the radial gradient is either constant in angle or continuous, becoming steeper as the distance from the axis of rotation A increases. These two methods of defining the radial gradient compensate for two main deformation patterns resulting from the formation of the wear protection layer. In particular, a constant gradient is suitable when the ring surface is inclined across the entire width of the ring, for example, because the internally positioned hub fixture deforms as a result of thermally induced stress. A continuous radial gradient that becomes steeper outward can compensate for bowl-shaped deformation across the width of the friction ring.
[0014] Optionally, the formation of the wear protection layer includes a thermal coating process such as laser metal deposition, in which the wear protection layer is applied to the substrate (particularly the friction surface region), or is formed on the substrate (particularly the friction surface region) in a thermal diffusion process such as nitriding.
[0015] In this method, the wear protection layer is preferably formed by laser metal deposition. This method involves high heat input to the substrate, resulting in thermally induced stress and strain, but this can be compensated for by a radial gradient during prefabrication. During laser metal deposition, the outer surfaces of the two friction surfaces to be coated are melted by a laser beam, and coating powder is supplied onto the molten friction surfaces. Preferably, the coating powder is at least partially liquefied by the laser beam before reaching the molten friction surfaces. This creates a material bond between the friction surfaces and the coating powder, forming the wear protection layer.
[0016] Optionally, the method may include a step of (c) after the formation of the wear protection layer, smoothing the friction surface, preferably by grinding, so that the friction surface is aligned in a direction perpendicular to the axis of rotation. This can reduce surface roughness at least. In addition, it is possible to equalize misalignment and runout that affect the friction surface.
[0017] Specifically, after smoothing, the thickness of the wear protection layer on one or both friction surfaces may have a thickness variation of less than 50%, preferably less than 30%. The thickness variation is defined in particular as the difference between the maximum and minimum thicknesses divided by the minimum thickness. This results in a nearly uniform thickness of the wear layer, reducing particulate matter emissions and achieving a longer service life.
[0018] During the prefabrication of the substrate, the annular friction surfaces should be formed rotationally symmetrically. This brings the friction surfaces closer to the target shape, and it is generally expected that other thermal distortions affecting the surroundings will not occur during the formation of the wear protection layer, especially when not using laser metal deposition. Furthermore, during the prefabrication of the substrate, the annular friction surfaces should be oriented parallel to each other. This also brings the friction ring closer to the target shape.
[0019] In a modified version of this method, during the prefabrication of the substrate after casting, the annular friction surface and hub contact surface are oriented to be at least substantially or completely perpendicular to the axis of rotation, and the radial gradient is increased or exclusively formed by material removal (which is required in this case) in the region of the friction surface and / or the region of the hub contact surface. As a result, this method is readily applicable because material removal can be easily handled, in contrast to adjusting the mold, if the mold already has friction and hub contact surfaces arranged perpendicularly. Furthermore, by adjusting the material removal, the radial gradient can be corrected as part of quality control in the manufacturing process.
[0020] Optionally, the method may include inspecting the radial residual gradient of at least one friction surface after the formation of a wear protection layer, particularly by measuring it with a measuring probe, and correcting the radial gradient during the prefabrication of the next substrate such that the friction surface after the formation of the wear protection layer has a predicted radial residual gradient smaller than the radial residual gradient of the inspected friction surface. The advantage of this verification is that it improves the reliability of the manufacturing process with respect to the radial residual gradient of the friction surface. Casting quality and tool wear in any material removal during prefabrication, for example, affect the radial gradient of the friction surface during prefabrication. Process parameters for forming the wear protection layer may also affect the thermal strain of the friction surface. By inspecting the radial residual gradient, it becomes possible to apply mechanical parameters to form a predetermined radial gradient in the prefabrication process, preferably automatically, to make corrections.
[0021] Furthermore, the method may include forming an intermediate layer on one or both friction surfaces before forming the wear protection layer (a2). Such an intermediate layer can improve the adhesion and peel resistance of the coating. [Brief explanation of the drawing]
[0022] Further features, details, and advantages of the present invention will become apparent from the wording of the claims and the following description of exemplary embodiments with reference to the drawings. [Figure 1a] It is a diagram showing a schematic view of a brake disc after preliminary manufacture of a substrate according to the prior art. [Figure 1b] It is a diagram showing a schematic view of the brake disc in Fig. 1a after forming a wear protection layer on the friction surface. [Figure 1c] It is a diagram showing a schematic view of the brake disc in Fig. 1b after smoothing the friction surface. [Figure 2a] It is a diagram showing a schematic view of a brake disc after preliminary manufacture of a substrate according to the present invention. [Figure 2b] It is a diagram showing a schematic view of the brake disc shown in Fig. 2a after forming a wear protection layer on the friction surface. [Figure 2c] It is a diagram showing a schematic view of the brake disc shown in Fig. 2b after smoothing the friction surface.
Embodiments for Carrying Out the Invention
[0023] Figs. 1a, 1b, 1c, 2a, 2b, and 2c each show a schematic view of a brake disc 1. Therefore, a common description regarding the drawings will be given first. The reference numerals refer to the respective corresponding features. The brake disc 1 includes a substrate 2 having a friction ring 3 made of metal, preferably cast iron. The friction ring 3 has two annular friction surfaces 4 and 5 that are arranged parallel to each other and extend rotationally symmetrically about the (virtual) rotation axis A of the substrate 2. Each of the annular friction surfaces 4 and 5 has a ring width B that extends between an inner diameter RI and an outer diameter RA (reference numerals are shown only in Figs. 1a and 2a). The substrate 2 has a hub fixing portion 6 integrally formed with the friction ring 3 and includes a hub contact surface 7 that extends in a direction orthogonal to the rotation axis A. Thereby, the friction ring 3 is arranged on the hub fixing portion 6. Similarly, the (virtual) plane E is also oriented orthogonal to the rotation axis A.
[0024] The base body 2 of the brake disk 1 in Fig. 1a is manufactured by casting metal and, optionally, removing material in the region of the friction surfaces 4, 5 such that the annular friction surfaces 4, 5 are orthogonal to the axis of rotation A and / or parallel to the plane E. When forming the wear protection layer 10 on the two friction surfaces 4, 5 using a method involving heat input, particularly the laser metal deposition method, the friction ring 3 is deformed as shown in Fig. 1b due to thermal stress. The entire friction ring with the friction surfaces 4, 5 and the wear protection layer 10 forms an angle with respect to the plane E. When viewed in the circumferential direction, the friction surfaces can be represented as the side surface of a flat truncated cone. As shown in Fig. 1c, it is possible to correct this angle by smoothing the friction surfaces 4, 5, particularly the wear protection layer 10, and arranging the friction surfaces 4, 5 parallel to the plane E again. However, for example, as shown in Fig. 1c by microscopic examination, it is clear that the wear protection layer 10 has significant differences in layer thickness over the friction ring width B. During use, this can result in a situation where the wear protection layer 10 has already worn in the regions with a thin layer thickness, while still being effective in the regions with a thick layer thickness. As a result, even in a relatively early wear state, the discharge of fine particulate matter from the grey cast iron part of the friction ring 3 increases. Furthermore, since the cooperating brake pads wear unevenly, the friction surfaces 4, 5 begin to incline with respect to the plane E as the service life progresses.
[0025] Accordingly, according to the present invention, as shown in Figure 2a, in the manufacturing process, a base body 2 equipped with a metal friction ring 3 is pre-fabricated such that, after casting the base body 2 from metal and removing material in the areas of the friction surfaces 4 and 5 as needed, these friction surfaces 4 and 5 have a radial gradient W1 with respect to the hub contact surface 7 (and also with respect to the orthogonal plane E in the exemplary embodiment). This radial gradient W1 is selected empirically so that the subsequent formation of the wear protection layer 10 on the two friction surfaces 4 and 5 causes deformation such that the radial gradient W1 of the friction surfaces 4 and 5 decreases to a radial residual gradient W2, as shown in Figure 2b, due to the thermally induced stress in this process, so that the radial gradient W1 of the friction surfaces 4 and 5 becomes as close as possible to 0° with respect to the plane E. Optionally, an intermediate layer 11 can also be formed on the friction surfaces 4 and 5 before the formation of the wear protection layer 10. If these generate thermal stress in the base body 2, they can be compensated for in the next step of forming the wear protection layer 10. For this purpose, it is sufficient to consider this when defining the radial gradient W1.
[0026] In terms of absolute values, the prefabrication of the substrate 2 should actually result in the inner diameter RI having an offset V of 10 μm to 90 μm, preferably 30 μm to 70 μm, relative to the outer diameter RA, along an axis perpendicular to the hub contact surface 7 (and also along the rotation axis A in exemplary embodiments). The gradient W1 forming this offset does not need to be linear, since thermal stress does not necessarily result in a purely angular change. Therefore, it is quite possible for the friction surfaces 4 and 5 shown in Figure 2a to have curvature across the ring width B to form a radial gradient W1. Typically, the radial gradient W1 should be formed continuously and increase from the inner diameter RI towards the outer diameter RA. This makes it possible to counteract bowl-shaped deformation due to thermal stress. Therefore, nonlinearity can result in particularly high shape accuracy after the formation of the wear protection layer 10. Technically, it is somewhat simpler to form the radial gradient W1 as a constant angle.
[0027] After the formation of the wear protection layer 10, the radial residual gradient W2 is preferably 0°, which is preferably at least substantially linear across the ring width B. However, cases where the objective is not fully achieved are also within the scope of the invention. For example, after the formation of the wear protection layer 10, it may be sufficient for the inner diameter RI along an axis perpendicular to the hub contact surface (and in exemplary embodiments, along the rotation axis A) to have an offset V of less than 50 μm, preferably less than 30 μm, relative to the outer diameter RA. Depending on the thickness of the wear protection layer 10, this may be sufficient for the maximum possible uniform thickness after smoothing, as illustrated in Figure 2c. This objective is also achieved, in particular, when the radial residual gradient W2 has the opposite sign to the initial radial gradient W1. In relative terms, the thickness D of the wear protection layer 10 on the smoothed friction surfaces 4, 5 should have a thickness variation of less than 50%, preferably less than 30%, respectively. This is especially true when the thickness variation is defined as the difference between the maximum and minimum thicknesses divided by the minimum thickness.
[0028] Optionally, during the prefabrication of the cast substrate 2, the annular friction surfaces 4, 5 and the hub contact surface 7 may be positioned at least substantially or completely perpendicular to the axis of rotation A, and the radial gradient W1 (as shown in Figure 2a) may be increased or formed solely by material removal in the area of the friction surfaces 4, 5. This makes it possible, for example, to use an existing mold in this method. Material removal provides high flexibility with respect to the radial gradient W1 (e.g., linear or nonlinear gradient) by inspecting the residual radial gradient W2 in particular and correcting the radial gradient W1 in the next manufacturing cycle based on the results.
[0029] For example, the method may include, in particular, inspecting, measuring (e.g., using a measuring probe), the radial residual gradient W2 of at least one of the two friction surfaces 4, 5 after the formation of the wear protection layer 10, and then, during the prefabrication of the next substrate 2', modifying the radial gradient W1' such that, after the formation of the wear protection layer 10', its friction surfaces 4', 5' have a predicted residual gradient W2' that is smaller than the residual gradient of the inspected friction surfaces 4, 5.
[0030] The present invention is not limited to any of the embodiments described above and can be modified in various ways.
[0031] All features and advantages evident from the claims, detailed description, and drawings, including structural details, spatial arrangement, and method steps, can be essential to the present invention, individually or in a wide variety of combinations. [Explanation of Symbols]
[0032] 1 Brake Disc 2 Base 3 friction rings 4,5 Friction surface 6 Hub fixing part 7 Hub contact surface 10. Abrasion protection layer 11 Middle Class A rotation axis B Ring width E orthogonal plane RI inner diameter RA outer diameter W1 Radial gradient W2 Radial residual gradient V Offset
Claims
1. A method for manufacturing a brake disc (1), a) A base body (2) comprising a hub fixing portion (6) and a friction ring (3) made of metal, wherein the hub fixing portion (6) has an annular hub contact surface (7) and the friction ring (3) has two opposing annular friction surfaces (4, 5) extending around the rotation axis (A) of the base body (2), a. The base body (2) is cast from metal, b. Optionally, by removing material from the area of the friction surfaces (4, 5) and / or the area of the hub contact surface (7), The steps include pre-manufacturing the annular friction surfaces (4, 5) such that they have a radial gradient (W1) with respect to the hub contact surface (7), b) A step of forming a wear protection layer (10) on either or both of the friction surfaces (4, 5) such that the thermally induced stress in this process deforms the annular friction surfaces (4, 5) in such a way that the absolute value of the radial gradient (W1) is reduced to a lower absolute value of the radial residual gradient (W2), A method that includes this.
2. The method according to claim 1, wherein, after the formation of the wear protection layer (10), the radial residual gradient (W2) becomes substantially or completely 0°, thereby orienting the friction surfaces (4, 5) in a direction at least substantially or completely perpendicular to the axis of rotation (A).
3. The method according to claim 1 or claim 2, wherein the friction surfaces (4, 5) each have a ring width (B) with an inner diameter (RI) and an outer diameter (RA), and during the prefabrication of the base body (2), the radial gradient (W1) of the friction surfaces (4, 5) is formed such that the inner diameter (RI) is offset (V) with respect to the outer diameter (RA) along an axis perpendicular to the hub contact surface (7), and the absolute value of the offset is between 10 μm and 90 μm, preferably between 30 μm and 70 μm.
4. The method according to any one of claims 1 to 3, wherein the friction surfaces (4, 5) each have a ring width (B) with an inner diameter (RI) and an outer diameter (RA), and after the formation of the wear protection layer (10), the radial residual gradient (W2) is formed such that the inner diameter (RI) has an offset (V) with respect to the outer diameter (RA) along an axis perpendicular to the hub contact surface (7), and the absolute value of the offset is less than 50 μm, preferably less than 30 μm.
5. The method according to any one of claims 1 to 4, wherein the radial gradient (W1) is at a constant angle, or the radial gradient (W1) is continuous and becomes steeper as the distance from the axis of rotation (A) increases.
6. The method according to any one of claims 1 to 5, wherein the wear protection layer (10) is formed by laser metal deposition.
7. c) The method according to any one of claims 1 to 6, comprising the step of smoothing the friction surfaces (4, 5) after the formation of the wear protection layer (10).
8. The method according to claim 7, wherein, after smoothing, the thickness (D) of the wear protection layer (10) on one or both of the friction surfaces (4, 5) has a thickness variation of less than 50%, preferably less than 30%.
9. The method according to any one of claims 1 to 8, wherein during the prefabrication of the substrate (2) after casting, the annular friction surfaces (4, 5) and the hub contact surface (7) are positioned at least substantially or completely perpendicular to the axis of rotation (A), and the radial gradient (W1) is increased or exclusively generated by the removal of material in the area of the friction surfaces (4, 5) and / or the area of the hub contact surface (7).
10. d) The method according to any one of claims 1 to 9, comprising the step of inspecting the radial residual gradient (W2) of at least one of the two friction surfaces (4, 5) after the formation of the wear protection layer (10), and correcting the radial gradient (W1') during the prefabrication of the next substrate (2'), after the formation of the wear protection layer (10'), such that the friction surfaces (4', 5') have an expected radial residual gradient (W2') that is smaller than the radial residual gradient (W2) of the inspected friction surfaces (4, 5).
11. a2) The method according to any one of claims 1 to 10, comprising the step of forming an intermediate layer (11) on either or both of the friction surfaces (4, 5) before forming the wear protection layer (10).