Coated brake disc for a motor vehicle and motor vehicle with such a brake disc

Abstract

The invention relates to a coated brake disc (2) for a motor vehicle, rotatable about an axis of rotation (4), with at least one base body (6), with at least one wear-prone friction layer (8) which is fixed to the base body (6) as an additional coating and which forms a braking surface (12) on the side facing away from the base body (6), on which a braking agent comes into contact and causes wear when the vehicle is braked, wherein the friction layer (8) is formed from a mixture of nickel-free stainless steel and a titanium compound.

Description

[0001] The invention relates to a coated brake disc for a motor vehicle and to a motor vehicle with such a brake disc.

[0002] Brake discs made of gray cast iron are known from the prior art. To brake the vehicle, a brake fluid is applied to the brake disc, which means that magnetic or magnetizable brake dust can never be completely avoided.

[0003] Legal regulations, such as Euro 7, limit the mass of brake particles with an aerodynamic diameter of between 10 µm and 10 nm. Such a restriction encompasses the particulate mass (PM), currently PM10. To further limit vehicle emissions in the future, it is likely that the particulate mass will be further reduced and, if necessary, the number of emitted brake particles will be limited.

[0004] To reduce brake particle emissions, the use of coated brake discs is already known in the art. With coated brake discs, the base body, which may, for example, be made of gray cast iron, is coated with a hard material and / or a similar material to form a friction layer.

[0005] This additional friction layer made of hard material serves as a friction surface against which a brake fluid can be applied when the vehicle brakes. Known friction layer thicknesses of coated brake discs are very thin, ranging from approximately 100 to 300 µm.

[0006] One object of an embodiment of the invention is to propose a coated brake disc for a motor vehicle and a motor vehicle with such a brake disc in which the emission of brake particles during a braking process can be further reduced.

[0007] This problem is solved by a coated brake disc for a motor vehicle, rotatable about an axis of rotation, with at least one base body, with at least one wear-prone friction layer, which is fixed to the base body as an additional coating and which forms a braking surface on the side facing away from the base body, on which a braking agent is in contact and causes wear when the vehicle is braked, wherein the friction layer is formed from a mixture of nickel-free stainless steel and a titanium compound.

[0008] Because the coated brake disc includes a friction layer on the base body, which is formed from a mixture of nickel-free stainless steel and a titanium compound, mechanical brake abrasion can be reduced.

[0009] It has surprisingly turned out that by using a friction layer made of nickel-free stainless steel and a titanium compound, the particle mass of the brake abrasion can be reduced by up to more than 50% compared to brake discs made exclusively of a cast iron base.

[0010] Furthermore, it has proven advantageous that when using a friction layer comprising nickel-free stainless steel and a titanium alloy, the reduction of brake particle mass can be further reduced compared to coated brake discs that include pure stainless steel as a coating.

[0011] This allows both brake abrasion and the mass of brake abrasion to be reduced by the coated brake disc according to the invention.

[0012] Furthermore, by providing a friction layer made of a mixture of nickel-free stainless steel and a titanium compound, the service life of the brake disc is increased and, due to the rust-free properties, a braking surface is always provided that operates with reduced noise during braking and, especially compared to cast iron brake discs, its braking performance is not affected by rust formation.

[0013] It is conceivable to find methods for manufacturing the brake disc in which the titanium compound comprises a titanium carbide (TiC), in particular chemically pure, or a compound based on titanium carbide-ferrochrome (TiC+FeCr), in particular agglomerated and sintered.

[0014] If the titanium compound comprises titanium carbide, particularly chemically pure titanium carbide, it may, for example, have an irregular structure and be broken powder. The titanium compound may also contain small amounts of, for example, unbound carbon, iron, or oxygen. These small amounts comprise a maximum of 0.3% each.

[0015] If the titanium compound includes a titanium carbide-ferrochrome compound, especially an agglomerated and sintered one, it can break up when applied to the base body, for example as a result of laser cladding, and mix more finely with the nickel-free stainless steel.

[0016] This ensures that when a grain is removed from a titanium compound as a result of a braking process, no or smaller depressions are formed in the braking surface.

[0017] In principle, it is conceivable that the friction layer is directly bonded to the base body. However, it proves advantageous if the brake disc includes at least one intermediate layer, which is bonded to the base body as an additional coating between the base body and the friction layer, and to which the friction layer is bonded, with the intermediate layer being made of nickel-free stainless steel.

[0018] The intermediate layer provides improved thermal conductivity and a certain degree of elasticity between the base material, the grey cast iron, and the friction layer.

[0019] It proves advantageous if the nickel-free stainless steel of the intermediate layer and / or the friction layer comprises AISI 430L and / or if the friction layer is formed from at least 50% nickel-free stainless steel and a maximum of 50% titanium compound, in particular from at least 60% nickel-free stainless steel and a maximum of 40% titanium compound, in particular from at least 70% nickel-free stainless steel and a maximum of 30% titanium compound.

[0020] The intermediate layer, made of nickel-free stainless steel, improves the thermal conductivity of the brake disc in this area. The friction layer, composed of at least 50% nickel-free stainless steel and a maximum of 50% titanium compound, allows for the use of compounds, alloys, or mixtures optimized for abrasion resistance and reduction of brake particle count and size.

[0021] The brake disc can, in principle, be manufactured in any desired manner. It proves advantageous if the intermediate layer is bonded to the base body by means of laser cladding and / or if the friction layer is bonded to the base body or to the intermediate layer by means of laser cladding, wherein the nickel-free stainless steel and / or the titanium compound are provided in powder form for laser cladding, and wherein, in particular, the titanium compound provided in powder form comprises a grain size of 5 µm to 60 µm, in particular of 10 µm to 50 µm, and in particular of 15 µm to 45 µm.

[0022] When the intermediate layer is bonded to the base body by means of laser cladding, the nickel-free stainless steel, in particular AISI 430L, is melted in a powdered state by laser cladding and bonded to the base body.

[0023] The same applies to the application of the friction layer to the intermediate layer or the base body. When applying the friction layer using laser cladding, the addition of the titanium compound is also a factor.

[0024] Laser cladding melts the nickel-free stainless steel, while the titanium compound remains in a solid state. For example, if the titanium compound includes titanium carbide, this is incorporated into the molten stainless steel during laser cladding without changing its state.

[0025] If the titanium compound contains a titanium carbide ferrochrome, laser cladding can liquefy the ferrochrome and break down the titanium carbide into smaller grains. This results in a more homogeneous distribution of the titanium compound in the friction layer.

[0026] The quality of the brake disc can be further improved if the base body, on the surface facing the friction layer where the intermediate layer or the friction layer is located, has an average roughness depth (Rz) of 4 µm to 12 µm, in particular of 7 µm to 9 µm, and a mean roughness value (Ra) of 1 µm, and / or if the friction layer, on the surface facing away from the base body and forming the braking surface, has an average roughness depth (Rz) of a maximum of 7 µm, in particular a maximum of 5 µm, in particular a maximum of 3 µm, and a mean roughness value (Ra) of 0.4 µm.

[0027] To further improve the quality of the brake disc, in particular to protect the base body against corrosion, it is advantageous if the brake disc comprises at least one corrosion-protective coating arranged on the side of the base body facing the friction layer, wherein the coating contains zinc and in particular comprises Geomet 360 with an addition of nitrosyl fluoride and / or Magni C40.

[0028] Furthermore, embodiments of the brake disc prove to be advantageous in which the base body comprises a grey cast iron, in which the friction layer comprises a friction layer thickness of 100 µm to 300 µm, in particular of 100 µm to 200 µm, in particular of 150 µm to 200 µm, and / or in which the intermediate layer comprises an intermediate layer thickness of 100 µm to 300 µm, in particular of 100 µm to 200 µm, in particular of 150 µm to 200 µm.

[0029] In order to facilitate inspection of the brake disc due to the small friction layer thicknesses, in particular to determine whether the friction layer still has a sufficiently large friction layer thickness, it proves advantageous if the brake disc includes at least one wear indicator which is arranged in the braking surface of the friction layer, which is visually perceptible until a critical friction layer thickness of the friction layer is reached or fallen below, at which point the friction layer is almost worn away, and which is worn away from the point at which the critical friction layer thickness of the friction layer is reached or fallen below.

[0030] The at least one wear indicator can include a recess in the friction layer. This recess can be designed as a material-free depression.

[0031] The recess can extend from the braking surface of the friction layer parallel to the axis of rotation towards the base body and be open to the outside on the side facing away from the base body.

[0032] The at least one wear indicator can have a diameter of 2.5 to 7.5 mm. Preferred embodiments are those in which the wear indicator has a diameter of 3 mm transverse to the axis of rotation.

[0033] In further developments of the brake disc, at least three wear indicators can be arranged in the friction layer. Furthermore, embodiments of the brake disc are conceivable in which at least one friction layer is arranged on the base body on both the side facing the center of the vehicle and the side facing away from the center of the vehicle, and at least one, and in particular at least three, wear indicators are arranged in each of the friction layers.

[0034] The at least one wear indicator can be designed such that it is considered worn away when the friction layer thickness falls below 80% of the original, unworn friction layer thickness. In this case, the critical friction layer thickness can be between 20 and 40 µm.

[0035] At least one of the at least one wear indicator can have a polygonal, in particular triangular or quadrilateral, a rounded, in particular circular or elliptical, a dot-like, a line-like or an arrow-like cross-section. Furthermore, it is conceivable that at least one of the at least one wear indicator includes a representation, such as a logo, in its cross-section.

[0036] If multiple wear indicators are provided in the friction layer, they can be arranged evenly or unevenly distributed within the friction layer at the same or different angles to each other with respect to the axis of rotation. Furthermore, embodiments of the brake disc are conceivable in which, if multiple wear indicators are provided, each wear indicator has the same distance with respect to the axis of rotation, or in which any two wear indicators have a different distance with respect to the axis of rotation.

[0037] Furthermore, embodiments of the brake disc are conceivable where, for example, it includes several wear indicators, such that each wear indicator is activated once its own critical friction layer thickness is reached. For instance, it is conceivable that a first wear indicator is activated when 50% of the friction layer has been worn away, and another wear indicator, for example, when 20% of the original friction layer has been reached. This makes it easier to determine the remaining thickness of the friction layer during an inspection, without the need for tools.

[0038] Finally, the problem is solved by a motor vehicle with at least one brake disc having at least one of the aforementioned features.

[0039] The following qualitative figures illustrate the emission improvements for a brake disc consisting of a cast iron base. The base itself, without any coating, represents the starting point (100%) for considering the qualitative emission improvement.

[0040] The table shows that a brake disc comprising a coating consisting of 70% stainless steel, in particular 430L and 30% titanium carbide, produces only 45% of the emissions compared to a brake disc made entirely of cast iron. brake disc Cast iron, no hard coating Cast iron 100% 430L coating Cast iron 30% TiC + 70% 430L coating Brake fluid Low Met + Cu Low Met without Cu Low Met without Cu PM10 emissions 100% 75% 45%

[0041] The term "Low Met" stands for "low metallic". Brake fluids in this category can contain fibers made of glass, rubber, carbon, or aramid, mixed with a metal content of 10 to 30%, usually copper or steel.

[0042] Further features, details and advantages of the invention will become apparent from the attached patent claims, the graphic representation and the following description of two preferred embodiments of the brake disc.

[0043] The drawing shows: Fig. 1 A side sectional view of an embodiment of the coated brake disc; Fig. 2 A schematic representation of a first embodiment of the titanium compound; Fig. 3 A schematic representation of a second embodiment of the titanium compound; Fig. 4 A top view of a second embodiment of a coated brake disc; Fig. 5 A detailed view of the coated brake disc according to Fig. 4 in the area of ​​a wear indicator.

[0044] The Fig. 1 and Fig.Figures 4 each show an embodiment of a coated brake disc for a motor vehicle, the entire disc being designated with reference numeral 2. The brake discs 2 are each rotatable about an axis of rotation 4.

[0045] The brake discs 2 each comprise a base body 6 and a wear-prone friction layer 8. In the embodiments shown in the figures, an intermediate layer 10 is provided between the base body 6 and the friction layer 8. In this case, the friction layer 8 is fixed to the intermediate layer 10, and the intermediate layer 10 is fixed to the base body 6. On the side facing away from the base body 6, the friction layer 8 forms a braking surface 12, against which a braking fluid comes into contact during braking, thus generating wear.

[0046] In the embodiments of the coated brake disc 2 shown in the figures, the friction layers 8 are formed from a mixture of nickel-free stainless steel and a titanium compound.

[0047] Fig. Figure 1 shows a first embodiment of the coated brake disc 2 with a detailed view in the area of ​​the friction layer 8. The friction layer 8 and the intermediate layer 10 each comprise layer thicknesses that can range from 100 µm to 300 µm.

[0048] According to the presentation Fig. Figure 1 shows that in the friction layer 8 the titanium compound is distributed in a granular manner in the nickel-free stainless steel.

[0049] Fig. Figure 2 shows a schematic representation of a first embodiment of a titanium compound. In this embodiment, the titanium compound is formed from titanium carbide and has an irregular shape.

[0050] Fig. Figure 3 shows a second embodiment of the titanium compound, in which the titanium compound consists of a titanium carbide-ferrochrome compound. Such a titanium compound is agglomerated and sintered and has a spherical contour.

[0051] Fig. Figure 4 shows a top view of a second embodiment of the coated brake disc 2, in which several wear indicators 14 are arranged in the braking surface 12 of the friction layer 8.

[0052] At the in Fig. In the exemplary embodiment shown in Figure 4, three wear indicators 14 are provided, which are spaced uniformly apart from each other in the circumferential direction with respect to the axis of rotation 4, i.e., in 120° increments. Furthermore, in the exemplary embodiment shown in Figure 4, each of the wear indicators 14 comprises Fig. 4, a different distance to the axis of rotation 4.

[0053] Fig. Figure 5 shows a detailed view of the coated brake disc 2 according to Fig. 4 in the area of ​​the wear indicator 14. From the illustration according to Fig.As can be seen in Figure 5, the wear indicator 14 is formed by a material-free depression in the friction layer 8 and has a depth that is essentially 80% of the thickness of the friction layer 8. This means that when the friction layer 8 has worn away to the base of the wear indicator 14, the wear indicator 14 is no longer visible from the outside. This allows for visual inspection of the vehicle, particularly without tools, to determine whether the brake disc 2 needs to be replaced or refurbished.

[0054] The features of the invention disclosed in the foregoing description, in the claims and in the drawing may be essential, both individually and in any combination, in the realization of the invention in its various embodiments within the scope of protection of the following claims. Reference symbol list 2 brake discs 4 axis of rotation 6 basic shapes 8 friction layer 10 Intermediate shift 12 Braking surface 14 Wear indicator

Claims

[1] Coated brake disc (2) for a motor vehicle, rotatable about an axis of rotation (4), comprising at least one base body (6), comprising at least one wear-prone friction layer (8) which is fixed to the base body (6) as an additional coating and which forms a braking surface (12) on the side facing away from the base body (6), on which a braking medium comes into contact and causes wear when the vehicle is braked, wherein the friction layer (8) is formed from a mixture of nickel-free stainless steel and a titanium compound. [2] Brake disc (2) according to claim 1, characterized by that the titanium compound comprises a titanium carbide (TiC), in particular chemically pure, or a compound based on titanium carbide ferrochrome (TiC+FeCr), in particular agglomerated and sintered. [3] Brake disc (2) according to claim 1 or 2, characterized byat least one intermediate layer (10) which is fixed to the base body (6) as an additional coating between the base body (6) and the friction layer (8) and to which the friction layer (8) is fixed, wherein the intermediate layer (10) is formed from a nickel-free stainless steel. [4] Brake disc (2) according to one of the preceding claims, characterized by , that the nickel-free stainless steel of the intermediate layer (10) and / or the friction layer (8) comprises AISI 430L and / or that the friction layer (8) is formed of at least 50% nickel-free stainless steel and a maximum of 50% titanium compound, in particular of at least 60% nickel-free stainless steel and a maximum of 40% titanium compound, in particular of at least 70% nickel-free stainless steel and a maximum of 30% titanium compound. [5] Brake disc (2) according to one of the preceding claims, characterized by, that the intermediate layer (10) is bonded to the base body (6) by means of laser cladding and / or that the friction layer (8) is bonded to the base body (6) or to the intermediate layer (10) by means of laser cladding, wherein the nickel-free stainless steel and / or the titanium compound are provided in powder form for laser cladding and wherein, in particular, the titanium compound provided in powder form comprises a grain size of 5 µm to 60 µm, in particular of 10 µm to 50 µm, in particular of 15 µm to 45 µm. [6] Brake disc (2) according to one of the preceding claims, characterized by, that the base body (6) on the surface facing the friction layer (8), on which the intermediate layer (10) or the friction layer (8) is fixed, comprises an average roughness depth (Rz) of 4 µm to 12 µm, in particular of 7 µm to 9 µm, and a mean roughness value (Ra) of 1 µm, and / or that the friction layer (8) on the surface facing away from the base body (6), forming the braking surface (12), comprises an average roughness depth (Rz) of a maximum of 7 µm, in particular a maximum of 5 µm, in particular a maximum of 3 µm, and a mean roughness value (Ra) of 0.4 µm. [7] Brake disc (2) according to one of the preceding claims, characterized by at least one corrosion-protective coating arranged on the side of the base body (6) facing the friction layer (8), wherein the coating comprises zinc and in particular Geomet 360 or Magni C40. [8] Brake disc (2) according to one of the preceding claims, characterized by, that the base body (6) comprises a grey cast iron, that the friction layer (8) comprises a friction layer thickness of 100 µm to 300 µm, in particular of 100 µm to 200 µm, in particular of 150 µm to 200 µm, and / or that the intermediate layer (10) comprises an intermediate layer thickness of 100 µm to 300 µm, in particular of 100 µm to 200 µm, in particular of 150 µm to 200 µm. [9] Brake disc (2) according to any one of the preceding claims, characterized by at least one wear indicator (14) which is arranged in the braking surface (12) of the friction layer (8), which is optically perceptible until a critical friction layer thickness of the friction layer (8) is reached or fallen below, at which point the friction layer (8) is almost worn away, and which is worn away from the point at which the critical friction layer thickness of the friction layer (8) is reached or fallen below. [10] Motor vehicle with at least one brake disc (2) according to any one of claims 1 to 9.

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