Structured brake disc

Abstract

A brake disc having a surface (S) which is structured to enhance the adhesion of a coating on the surface (S), wherein the structuring of the surface comprises at least one groove (G) whose width decreases as the depth of the recess increases, and wherein the at least one groove (G) has the shape of a spiral structure.

Description

[0001] The present invention relates to a brake disc having a treated surface, and in particular to a brake disc having a coating applied thereto with enhanced adhesion. The technicians call this process "surface activation", which is actually a kind of structuring. Background Art

[0002] DE102010064350A1 proposes a brake disc and a method for treating the surface of a brake disc, wherein the adhesion of a coating on the surface is enhanced by roughening the surface by adding at least one recess in the surface, the width of the recess increases as the depth of the recess increases, and a form-fitting connection is formed between the brake disc and the coating by means of the undercut.

[0003] For this purpose, the cutting tool has at least two cutting edges, wherein the two cutting edges are inclined at an angle relative to the perpendicular to the workpiece surface and the two cutting edges simultaneously form a common plane in an orthogonal direction. The aim here is to provide a precisely reproducible surface activation so that the surface coating can be applied to the activated surface with the smallest possible fluctuations in the process parameters.

[0004] According to the prior art, the surface is structured, wherein the structure comprises at least one recess, the width of which increases with increasing depth of the recess. The prior art describes that this allows a form-fit connection to be produced between a subsequently applied coating and the workpiece, wherein the form-fit connection is precisely reproducible.

[0005] Furthermore, it is advantageous according to this prior art if the at least one recess is in the form of a spiral recess, similar to the grooves on a record. This allows the surface to be activated by material removal, in particular by turning, which can be done very quickly and inexpensively.

[0006] However, corresponding structuring, which contains recesses whose width increases with increasing recess depth, has the serious disadvantage that this geometry produces a shadowing effect during subsequent coating. This means that with increasing recess depth, the coating thickness decreases significantly and the adhesion-improving effect is therefore significantly reduced. This is particularly problematic in coating processes such as plasma evaporation and vapor deposition (PVD processes), where the coating particles are directed straight from the material source to the substrate. The corresponding situation also applies to thermal spraying.

[0007] It is therefore necessary to provide a structuring in which, on the one hand, the coating has a toothed structure ensured by the undercuts and, on the other hand, the coating can reach directly into the structure without the structure being obscured by the widening of the recesses provided by the prior art.

[0008] This object is achieved according to the invention by a brake disk according to claim 1. In accordance with the prior art, the brake disk has at least one recess in the form of a spiral recess.

[0009] However, unlike the prior art, the width of the recess does not increase with increasing depth, but decreases. According to the present invention, a recess having a first groove wall and a second groove wall is realized. One of the two groove walls, for example the first groove wall, is designed as a groove wall that is concave relative to the surface to be coated. In contrast, the other groove wall, for example the second groove wall, is not designed as a concave groove wall. The width of the recess decreases with increasing recess depth. Correspondingly, no shielding occurs during coating in the other non-concave groove wall area.

[0010] Now combine Figure 1 The present invention will be described in detail with examples. Figure 1 A detail of a brake disc 1 to be coated according to the invention is schematically shown. The brake disc has a structured surface S to be coated with a groove G. The groove G can also be referred to as a recess. The groove G is a spiral recess milled into the surface S of the brake disc, which has a first groove wall W1 and a second groove wall W2. An imaginary rectangle is also drawn, which has an angle L (at the angle L formed by the groove wall W1 and the surface S) and another angle R (at the angle R formed by the groove wall W2 and the surface S). The height of the imaginary rectangle corresponds to the groove depth. The imaginary rectangle and the groove wall W1 form an angle α, which defines the steepness of the overhanging groove wall W1 and thus the undercut. The imaginary rectangle and the groove wall W2 form an angle β, which defines the steepness of the (non-overhanging) groove wall W2. According to the invention, the geometry of the recess is selected so that α>β applies, because it is thereby ensured that the width of the recess decreases with increasing depth.

[0011] In contrast, Figure 2 A recess according to the prior art is shown, in which α<β applies, so that the recess width increases with increasing depth.

[0012] Figure 3 A top view of a brake disc with spiral recesses is schematically shown. According to the invention, the coated brake disc 1 has a surface S, wherein the surface S has groove-like grooves G, such as in Figure 1 As can be clearly seen in the figure. The groove-shaped groove G comprises a first groove wall W1, a second groove wall W2 and a groove bottom N. The groove-shaped groove G has a width B measured from the first groove wall W1 to the second groove wall W in a manner approximately parallel to the surface S and a depth T measured from the surface S to the groove bottom N in a manner approximately perpendicular to the surface S. The width B decreases from the surface S toward the groove bottom N. This has the advantage that the second groove wall W2 can be well coated, especially in a coating process / coating method, because the coating particles can freely approach the second groove wall W2. At the same time, it is ensured that there are groove undercuts required to enhance the durable adhesion of the coating. And according to Figure 2 In the prior art, both groove walls are in the coating shadow area and can only be poorly coated.

[0013] In accordance with Figure 1It can be clearly seen in the embodiment of the invention that the second angle γ measured from the groove bottom N to the second groove wall W2 is greater than 90°, in particular between 90° and 180°, preferably 135° and in particular an obtuse angle. It can also be clearly seen that the first angle α measured from the groove bottom N to the first groove wall W1 is less than 90°, in particular between 0° and 90°, preferably 55° and in particular an acute angle. The supplementary angle β complementary to the second angle γ is less than the first angle α, wherein the second angle γ and the supplementary angle β add up to 180°. The groove-shaped groove G has a trapezoidal cross section, wherein in particular one of the two groove walls W1, W2, in particular the first groove wall W1, in particular the second groove wall W2 and particularly advantageously as according to Figure 1 In the embodiment shown in FIG. 1 , both groove walls W1, W2 are flat. A flat design can be produced relatively easily, especially when the groove G is milled. In another embodiment, it may be suitable that the walls W1, W2 are not flat, for example, have a circular, elliptical, parabolic, hyperbolic or other orientation in some areas. However, it is important that the width B of the groove G decreases, in particular decreases, in the direction from the surface S to the groove bottom N. It may be suitable that the width B of the groove G can be constant in some areas. It is particularly advantageous that the width B of the groove G at the surface S is greater than the width B of the groove G at the groove bottom N.

[0014] In accordance with Figure 1 In an embodiment of the present invention, the groove bottom N is flat and, in particular, extends approximately parallel to the surface S. In another embodiment, the groove bottom N can have a circular, elliptical, parabolic, hyperbolic or other course in some areas.

[0015] The depth T is smaller than the minimum width B of the groove G, wherein the minimum width B is in particular the width of the groove bottom N, in particular the ratio of the depth T to the minimum width B is approximately 0.85. This ratio is advantageously in the range of from about 0.5 to about 0.99, in particular in the range of from about 0.7 to about 0.95, advantageously in the range of from about 0.8 to about 0.9.

[0016] The depth T of the groove G is about 10 μm to 1000 μm. Figure 3 Clearly visible, the coated brake disk 1 is preferably characterized in that the grooves G on the surface S of the brake disk 1 extend approximately in a spiral shape. The center of the spiral is then approximately located in the center M of the circular brake disk 1, wherein the radius of the spiral decreases in particular towards the center M of the brake disk 1.

[0017] In one embodiment, a method for coating a brake disc is described below, wherein a brake disc 1 having a groove G is coated using a plasma evaporation process, in particular a PVD process, or by thermal spraying. In the coating method, coating particles shot from a coating source approximately straight toward the brake disc 1 hit the surface S of the brake disc 1 in a substantially orthogonal manner. Minor deviations from the orthogonality may also occur. However, it is important that the coating particles shot toward the brake disc 1 can at least directly approach one of the two groove walls W1, W2, in particular the second groove wall W2, so that the second groove wall W2 can be well coated. Appropriately, before the brake disc 1 is coated, the groove G is added to the brake disc surface, in particular by milling, scoring or cutting.

Claims

1. A brake disc (1) having a surface (S) which is structured to enhance the adhesion of a coating on the surface (S), wherein: The structuring of the surface comprises at least one groove-shaped groove (G), the width of which decreases as the depth of the recess increases, wherein the groove-shaped groove (G) has a first groove wall (W1), a second groove wall (W2) and a groove bottom (N), wherein the groove-shaped groove (G) has a width (B) measured from the first groove wall (W1) to the second groove wall (W2) in a manner parallel to the surface (S) and a depth (T) measured from the surface (S) to the groove bottom (N) in a manner perpendicular to the surface (S), wherein the width (B) decreases from the surface (S) to the groove bottom (N), wherein a first angle (α) measured from the groove bottom (N) to the first groove wall (W1) is between 0° and 90°, and wherein the at least one groove-shaped groove (G) has the shape of a spiral structure.

2. The brake disc according to claim 1, characterized in that The second angle (γ) measured from the groove bottom (N) to the second groove wall (W2) is between 90° and 180°.

3. The brake disc according to claim 2, characterized in that The supplementary angle (β) complementary to the second angle (γ) is smaller than the first angle (α), wherein the sum of the second angle (γ) and the supplementary angle (β) is 180°.

4. The brake disc according to any one of claims 1 to 3, characterized in that The groove-like groove (G) has a trapezoidal cross section.

5. The brake disc according to claim 1, characterized in that At least one of the first groove wall (W1) and the second groove wall (W2) is flat.

6. The brake disc according to claim 1, characterized in that The groove bottom (N) is flat and extends parallel to the surface (S).

7. The brake disc according to claim 1, wherein: The minimum width (B) is the width of the groove bottom (N), characterized in that the depth (T) is smaller than the minimum width (B) of the groove (G), and the ratio of the depth (T) to the minimum width (B) is 0.

85.

8. The brake disc according to claim 1, characterized in that The depth (T) is between 10 μm and 1000 μm.

9. The brake disc according to claim 1, characterized in that The groove (G) on the surface (S) of the brake disc (1) extends in a spiral shape, wherein the center of the spiral is at the center (M) of the circular brake disc (1), and wherein the radius of the spiral decreases towards the center (M) of the brake disc (1).

10. A method for coating a brake disc according to any one of claims 1 to 9, characterized in that The brake disc (1) having the grooves (G) is coated using a plasma evaporation process or by thermal spraying.

11. The method according to claim 10, characterized in that Coating particles projected straight from a coating source toward the brake disc (1) impact the surface (S) of the brake disc (1) in an orthogonal manner.

12. The method according to claim 10 or 11, characterized in that: The grooves (G) are introduced into the surface of the brake disc (1) before the brake disc (1) is coated.

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