Brake disc for a motor vehicle, motor vehicle and method for manufacturing a brake disc

Abstract

The invention relates to a brake disc (12) for a motor vehicle, said brake disc comprising a main body (20) made of a gray cast iron alloy and comprising a coating (22), wherein the coating (22) comprises different concentrations of hard materials in different regions.

Description

[0001] Brake disc for a motor vehicle, motor vehicle and method for manufacturing a brake disc

[0002] The invention relates to a brake disc for a motor vehicle, a motor vehicle with a brake disc, and a method for manufacturing a brake disc for a motor vehicle.

[0003] A brake disc for a friction brake of a motor vehicle is known from WO 2023 / 186347 A1. The brake disc comprises a friction section with at least one friction surface and a mounting section for attachment to the wheel side of the motor vehicle. The friction section and the mounting section are formed on a base body made of gray cast iron or steel. A wear-resistant layer is thermally applied to the friction section as the friction surface. An adhesion promoter layer is arranged between the wear-resistant layer and the base body, through which the wear-resistant layer is bonded to the base body. Color pigments are applied to the side of the adhesion promoter layer facing the wear-resistant layer, or the color pigments are embedded in the adhesion promoter layer.

[0004] The object of the present invention is to provide a solution that enables the provision of a brake disc with a particularly long service life.

[0005] 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.

[0006] The invention relates to a brake disc for a motor vehicle, in particular a car, and especially a passenger car. The brake disc is the wheel-side part of a disc brake, against which brake pads attached to a brake caliper act to slow down the rotation of the brake disc for braking the motor vehicle. The brake disc is, in particular, point-symmetrical about the axle center, and especially circular. The brake disc can comprise a brake disc hub and an annular friction disc held on the brake disc hub. It is particularly provided that the friction disc extends radially around the brake disc hub. This friction disc can provide a friction surface of the brake disc which can be brought into contact with the at least one brake pad for braking the motor vehicle. The brake disc hub is an axle mounting offset from the friction disc.This means that the brake disc is attached to an axle of the motor vehicle via the brake disc hub, and this axle is non-rotatably connected to at least one wheel of the motor vehicle, in particular to two wheels of the motor vehicle. By braking the brake disc as a result of frictional contact between the brake disc and the at least one brake pad, an axle of the motor vehicle, which is non-rotatably connected to at least one wheel and to the brake disc, can be braked.

[0007] The brake disc comprises a base body made of a gray cast iron alloy and a coating. The coating exhibits varying concentrations of hard materials in different areas. Specifically, the coating has different concentrations of hard materials in different surface areas. These hard materials are primarily carbides, such as titanium carbide, tungsten carbide, silicon carbide, or nickel carbide. By providing the coating with varying concentrations of hard materials in different areas, increased hardness can be achieved in specific regions with a higher concentration of hard materials.In particular, the areas with a higher concentration of hard materials in the coating are arranged in such a way that the coating exhibits the highest concentration of hard materials in areas subjected to particularly high loads during operation, thus resulting in a particularly hard coating, which in turn minimizes wear during operation. This allows for a particularly long service life of the brake disc.

[0008] In this context, a possible further development of the invention provides that the coating in at least one first surface area, which is intended to be in contact with the at least one brake pad during operation, has a higher concentration of hard materials than in at least one second surface area, which is intended not to be in contact with the brake pad during operation. The at least one first surface area is, for example, a so-called brake track, which is understood to be the surface of the brake disc coating that comes into frictional contact with the at least one brake pad when the vehicle is braked. The brake track extends, in particular, in a ring-like manner around a central axis of the brake disc at an end face of the brake disc.

[0009] It is possible that the at least one second surface area, which is not intended to come into contact with the at least one brake pad during operation, is kept free of hard particles. The hard particles, or rather the increased concentration of hard particles, are thus only present in the coating in areas that could come into contact with the brake pads during braking of the vehicle. To ensure that even with wear of the brake disc and thus with partial removal of the brake disc coating, the coating in the at least one surface area retains the increased concentration of hard particles, it is provided that the area of ​​increased hard particle concentration extends over the entire thickness of the at least one friction layer of the coating in the axial direction of the brake disc.The concentration of hard materials can be uniform across the entire area of ​​the friction layer that adjoins and is covered by at least one first surface area in the axial direction. The axial direction runs parallel to a longitudinal extension direction of the brake disc's central axis. The coating can therefore exhibit a sudden increase in the concentration of hard materials at a transition from a second surface area to a first surface area, for example, in the radial direction. For instance, the coating comprises two annular second surface areas, between which a first surface area is arranged radially, with all surface areas being arranged concentrically to one another.In this case, the concentration of hard particles in the coating can increase abruptly in the radial direction at the transition from the inner second surface area to the first surface area and decrease abruptly at the transition from the first surface area to the outer second surface area. If the concentration of hard particles is constant in the radial direction within each surface area, it can thus follow a rectangular curve. This coating configuration is particularly easy to manufacture.

[0010] Since the friction layer has different areas with varying concentrations of hard materials, the brake disc can be manufactured using very few of these materials. This allows for particularly cost-effective production of the brake disc and minimizes damage or wear to the production equipment used for manufacturing the brake disc due to contact with the hard materials. If the hard materials are conveyed through pipes in the production equipment, this can lead to abrasive wear of the pipes. The fewer hard materials conveyed through the pipes, the lower the wear and, consequently, the longer the production equipment's lifespan.The brake disc allows for a particularly low proportion of hard materials to be provided, while still achieving a particularly high durability of the brake disc due to the increased concentration of hard materials in areas of the coating that are particularly stressed during operation, especially the friction layer of the coating.

[0011] In a further possible embodiment of the invention, the concentration of hard materials in the at least one first surface area of ​​the coating, which is intended to be in contact with the brake pad during operation, has a value that changes continuously in the radial direction. When the at least one brake pad is pressed against the coating, in particular the friction layer of the brake disc coating, an increased frictional contact between the brake disc and the coating results in a partial area of ​​the first surface area, which is covered in the axial direction by at least one pressure element of the brake caliper, by means of which the brake pad is pressed axially against the brake disc.The pressure element thus presses the brake pad axially against the coating of the brake disc, whereby the brake pad in an area covering the pressure element in the axial direction is pressed against the coating of the brake disc with a greater force than areas of the brake pad which are not arranged in direct axial overlap with the pressure element or which are not directly pressed against the friction layer by means of the pressure element.

[0012] Because the concentration of hard particles in the coating exhibits a continuously changing value and thus a gradient in the radial direction, the varying stresses on the brake disc coating during operation can be accommodated. The greater the stress on specific areas of the first surface of the coating due to contact with the brake pad, the higher the concentration of hard particles in that area of ​​the coating. This allows for a particularly long service life of the brake disc while simultaneously ensuring an optimal amount of hard particles is used.

[0013] In this context, it is particularly advantageous that the concentration of hard particles in the coating first increases and then decreases with increasing radial distance from a central axis. This is especially beneficial when the brake pad is pressed against the brake disc coating by means of a pressure element, which is positioned in a central area on the outer surface of the brake pad facing away from the brake disc, with respect to the radial direction. This allows the brake pad to be pressed against the brake disc with particular reliability across its entire outer surface that comes into contact with the brake disc.By selecting the concentration of hard materials in the coating, which rises and then falls in a radial direction starting from the central axis of the brake disc, it can be achieved that the brake disc has a higher concentration of hard materials in areas that are particularly stressed during operation and is therefore subject to particularly low wear during operation.

[0014] In a further possible embodiment of the invention, the concentration of hard materials in the coating follows a Gaussian curve in the radial direction. The Gaussian curve can also be described as a bell curve. The concentration of hard materials in the coating is thus symmetrically distributed radially outwards from the central axis of the brake disc, with the highest concentration of hard materials occurring on a ring around the central axis of the brake disc. The concentration of hard materials in the friction layer decreases symmetrically along the radial direction from each point on this ring to opposite sides in the radial direction.This Gaussian distribution of concentration in the radial direction ensures that the concentration of hard materials in the first surface region is particularly well adapted to the load acting on this first surface region during operation due to contact with at least one brake pad. Alternatively, instead of the radial distribution of carbide concentration following a Gaussian curve, the radial distribution of carbide concentration can follow an arc, a rectangular curve, or any other curve.

[0015] In another possible embodiment of the invention, the coating is applied to the base body by laser cladding, cold gas spraying, or a combination of both methods. Laser cladding, which can also be referred to as laser metal deposition, is a type of cladding process in which the coating is applied to the base body by melting and simultaneously depositing the coating material. In particular, the coating, especially at least the friction layer of the coating, can be applied to the base body in powder form. In laser cladding, a high-power laser, in particular a diode laser or a fiber laser, serves as the heat source. Laser cladding allows the coating to be applied to the base body with high precision.Cold gas spraying is a coating process in which the coating material, in powder form, is applied at very high speed to a substrate, in this case the base material. For this purpose, a process gas heated to a few hundred degrees Celsius, particularly nitrogen, argon, or helium, is accelerated to supersonic speeds by expansion in a Laval nozzle, and the powder particles are then injected into the gas jet. The injected powder particles are accelerated to such a high speed that, unlike other thermal spraying processes, they form a dense and firmly adhering layer upon impact with the substrate without prior melting or annealing. Alternatively, the coating can be applied to the substrate using high-speed flame spraying.High-speed flame spraying involves continuous fuel combustion under high pressure within a water- or air-cooled combustion chamber. The high pressure of the burning fuel-oxidizer mixture generated in the combustion chamber, combined with an expansion nozzle, particularly a Laval nozzle, produces the necessary high velocity of the resulting gas jet, reaching speeds of up to 1300 m / s. A powdered spray material, which serves as the coating or friction layer material, is fed axially into the combustion chamber or radially in the area of ​​the expansion nozzle. This accelerates the spray material particles to high speed, causing them to impact a substrate, in this case, the base body. High-speed flame spraying enables the creation of particularly dense sprayed coatings with exceptionally good adhesion properties.

[0016] 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 motor vehicle can further have a brake caliper associated with this brake disc, which is configured to apply at least one, and in particular two, brake pads to the brake disc for braking the motor vehicle. The brake caliper can be configured to apply the brake pads to the brake disc from axially opposite sides. Due to the particularly wear-resistant design of the brake disc with an increased concentration of hard materials in areas of the coating subjected to high loads during operation, the brake disc has a particularly long service life.

[0017] The invention further relates to a method for manufacturing a brake disc for a motor vehicle. This brake disc can comprise a brake disc hub and an annular friction disc held on the brake disc hub. The brake disc comprises a base body made of a gray cast iron alloy with a coating. If the brake disc includes the friction disc, then this friction disc can encompass the base body with the coating. In the method, it is provided that, for the manufacture of the brake disc, the coating is applied to the base body with areas of varying concentration of hard materials. In particular, it is provided that the coating comprises a matrix material, especially Ti64, steel, or stainless steel, in which hard materials are integrated at least in certain areas.In this process, the coating is applied to the brake disc base in such a way that the coating, in particular a friction layer of the coating, has a higher concentration of hard materials in at least one first surface area, which is subject to increased stress during operation due to contact with at least one brake pad of the vehicle, compared to at least one second surface area, which is subject to lower stress during operation, for example, because no direct contact with brake pads of the vehicle is intended. The coating of the brake disc is thus particularly wear-resistant in the at least one first surface area due to the increased concentration of hard materials, resulting in a particularly long service life for the brake disc.

[0018] In a possible further development of the invention, it is provided that a powder is applied to the base body for the application of the coating, wherein the powder applied to the base body has a different concentration of hard particles in different areas. It is possible that the base body of the brake disc is first coated with an intermediate layer and that the friction layer is then applied to the intermediate layer in powder form. By applying the powder, the concentration of hard particles in the coating, especially in the friction layer of the coating, can be adjusted locally, particularly by setting the respective concentration of hard particles in the powder.In particular, the hard materials can be added to the powder very easily in a predetermined concentration, which makes it particularly easy to adjust the concentration in the different areas of the coating, especially the friction layer of the coating.

[0019] In this context, it is particularly advantageous for the powder to be applied to the base body in a spiral pattern. The powder can be applied to the base body of the annular brake disc in the direction of movement of a record player needle. For example, the powder can be applied radially outwards from a point located further radially inwards around the central axis of the brake disc. This allows for the easy creation of a continuous gradient of hard particles in the coating. Specifically, the concentration of hard particles in the coating can increase with increasing radial distance from the central axis of the annular brake disc and then decrease again.

[0020] 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 individually, without departing from the scope of the invention.

[0021] The drawing shows in:

[0022] Fig. 1 shows a schematic sectional view of a braking system for a motor vehicle with a brake disc and two brake pads applied to the brake disc; and

[0023] Fig. 2 shows a schematic side view of an annular brake disc.

[0024] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0025] Figure 1 shows a schematic sectional view of a brake system 10 for a motor vehicle. The brake system 10 comprises a brake disc 12 and two brake pads 14. In this illustration, one of the brake pads 14 is shown only with a dashed line. The brake disc 12 comprises a brake disc hub 16 and an annular friction disc 18, which radially surrounds the brake disc hub 16 and connects to it with its radial inner surface. To decelerate the motor vehicle, the brake pads 14 are applied to and pressed against the friction disc 18 on sides opposite each other in the axial direction A. For this purpose, the brake system 10 can include a brake caliper. The brake caliper, not shown in Figure 1, is designed to press the brake pads 14 against the opposing outer surfaces of the friction disc 18 in the axial direction A.The axial direction A runs parallel to a central axis 30 of the brake disc 12, which is designed to be rotationally symmetrical.

[0026] As can be seen in Fig. 1, the friction disc 18 is provided for in the present design to have a base body 20 made of a gray cast iron alloy, which is coated at least partially with a coating 22. In the present design, the base body 20 is coated with the coating 22 at least on its sides opposite each other in the axial direction A. The coating 22 can be a multi-layer system. This multi-layer system can, for example, comprise an intermediate layer and a friction layer, with the intermediate layer being arranged between the friction layer and the base body 20. It is provided that the coating 22 comprises at least the friction layer. The friction layer provides the outer surfaces of the coating 22 facing the brake pads 14.

[0027] Figure 2 shows a top view of the friction disc 18 from an end face of the brake disc 12. In this view, the axial direction A extends into the plane of the image. In other words, Figure 2 shows a top view of the outer surface of the friction disc 18 provided by the coating 22. Figure 2 shows a first surface area 24 and two second surface areas 26. The first surface area 24 is the area of ​​the outer surface of the coating 22 that, during normal operation of the brake disc 12, comes into contact with the brake pad 14 pressed against this outer surface of the coating 22. The second surface areas 26 are areas of the outer surface of the coating 22 that, during normal operation, are free from direct contact with the brake pad 14 associated with this side of the brake disc 12.The first surface area 24 is thus a braking surface of the brake disc 12, which, when the vehicle decelerates, forms a frictional contact with the brake pad 14 assigned to this side of the brake disc 12. It is provided that the coating 22 in the first surface area 24 has a higher concentration of hard materials than in the second surface areas 26. In particular, the friction layer of the coating 22 has a uniform concentration of hard materials over its entire thickness in the axial direction A. This means that the friction layer in an area covered by the first surface area 24 in the axial direction A has a uniform concentration of hard materials over its entire thickness in the axial direction A.Furthermore, the friction layer exhibits a uniform concentration of hard particles across its entire thickness in the axial direction A, within the areas covered by the second surface regions 26. This ensures that even with wear of the friction layer and subsequent removal of its thickness, the area of ​​the outer surface of the friction layer that comes into contact with the brake pad 14 for braking always retains a higher concentration of hard particles compared to the areas of the outer surface of the friction layer that do not come into contact with the brake pad 14 during operation. The coating 22 thus exhibits a different concentration of hard particles in different areas.

[0028] In Fig. 1, the concentration of hard materials is plotted as curve 28 against the coating 22. It can be seen that the concentration of hard materials in the coating 22 is designed to have a continuously changing value in the radial direction R. Thus, a concentration gradient of the hard materials is provided, at least in the first surface region 24, or in the region of the friction layer covered by the first surface region 24 in the axial direction A. As can be seen particularly well in Fig. 1, the concentration of hard materials in the coating 22 is designed to increase and then decrease with increasing radial distance from a central axis 30 of the friction disc 18, which is only indicated in Fig. 1. In particular, the concentration can increase and then decrease in the radial direction R according to the shape of a Gaussian curve.

[0029] To manufacture the brake disc 12, the coating 22, containing varying concentrations of hard materials in different areas, is applied to the base body 20. The coating 22 can be applied, at least partially, to the base body 20 in powder form. The powder applied to the base body 20 has varying concentrations of hard materials in different areas. Specifically, the powder can be applied in a spiral pattern around the central axis 30—with the central axis 30 as its center point—to the respective outer surfaces of the base body 20 that correspond to the brake pads 14. The coating of the base body 20 can be carried out by laser cladding, cold gas spraying, or high-speed flame spraying.

[0030] By incorporating hard materials into the coating 22, the brake disc 12 can be made to produce very little abrasion and consequently very little fine dust during operation, and wear of the brake disc 12 during operation can be kept to a minimum. As a result, a particularly long service life of the brake disc 12 can be achieved. To manufacture the brake disc 12, a single-layer, two-layer, or three-layer coating system is applied to the base body 20, which is made primarily of a gray cast iron alloy. Suitable coating processes include laser welding, plasma coating, high-speed flame spraying, laser cladding, cold gas spraying, or arc spraying. A two-layer coating system, for example, can consist of an intermediate layer, which can also be referred to as a bonding layer, and the friction layer.The intermediate layer results in particularly high strength of the brake disc 12, provides corrosion protection for the base body 20, ensures particularly high ductility of the brake disc 12, and facilitates excellent heat transfer from the friction layer to the base body 20 during operation, especially during braking. The friction layer is crucial for the braking effect of the brake disc 12. For particularly high wear resistance and to meet stringent particulate matter emission targets, the friction layer can comprise a matrix, particularly made of Ti64 or a stainless steel, into which hard materials such as carbides are incorporated. These carbides can be, in particular, tungsten carbide, titanium carbide, iron carbide, nickel carbide, or silicon carbide.The use of hard materials is costly, as they are expensive to manufacture, store and process, and can lead to high wear and tear on production facilities or manufacturing equipment for the brake disc 12.

[0031] Typically, the radial height of the brake pad 14 (R) is less than the outer surface of the coating 22 against which the brake pad 14 is applied for braking. The invention provides for the use of hard materials, particularly in those areas of the coating 22 where they are required due to potential contact with the brake pad 14. For coating the base body 20, carbide-containing powder can be fed into a manufacturing process by powder feeders, which in particular include at least one pump. Here, the base body 20 is coated radially outwards around the central axis 30, starting from the inside. For the coating process, a first powder feeder with matrix material powder and one or more powder feeders with carbide-containing matrix material powder can be used.During the coating process, the base body 20 is coated radially outwards around the central axis 30, starting from the inside, using the first powder feeder. After a radial length of 10 to 20 mm, the feeder either switches from the first powder feeder to one of the second powder feeders, e.g., containing carbide-containing powder, or the second powder feeder is added to the first powder feeder to apply the coating 22 to the base body 20 in the area of ​​the first surface region 24. At the radially outer area of ​​the coating 22, or to produce the area of ​​the coating 22 associated with the radially outer second surface region 26, the feeder switches back to the first powder feeder. This manufacturing process makes it possible to produce the brake disc 12 using very little carbide and thus with very low carbide consumption.Furthermore, the brake disc 12 can be manufactured with particularly low wear on the production equipment. Additionally, the base body 20 can be coated in the friction layer with pure matrix material without carbides in certain areas. This enables a particularly long service life for the friction disc 18, as it results in exceptionally high ductility and very few predetermined breaking points caused by carbides. The carbides are arranged in the coating 22 only according to the load, specifically in the form of a carbide gradient. Alternatively, instead of a Gaussian distribution, the carbide distribution in the coating 22 can follow the contour of a dome in the radial direction R.

[0032] Overall, the invention demonstrates how a load-oriented reinforcement of the brake disc 12 can be implemented. Reference numerals

[0033] 10 Braking system

[0034] 12 Brake disc

[0035] 14 brake pads

[0036] 16 brake disc hub

[0037] 18 friction disc

[0038] 20 basic shapes

[0039] 22 Coating

[0040] 24 first surface area

[0041] 26 second surface area

[0042] 28 Curve

[0043] 30 Center axis

[0044] axial direction

[0045] R radial direction

Claims

Patent claims 1. Brake disc (12) for a motor vehicle, comprising a base body (20) made of a grey cast iron alloy and a coating (22), wherein the coating (22) comprises a different concentration of hard materials in different areas.

2. Brake disc (12) according to claim 1, characterized by the fact that a brake pad (14) can be applied to the coating (22) during operation for braking the motor vehicle, and the coating (22) has a higher concentration of hard materials in at least a first surface area (24), which is intended to be contacted with the brake pad (14) during operation, than in at least a second surface area (26), which is intended not to be contacted with the brake pad (14) during operation.

3. Brake disc (12) according to claim 1 or 2, characterized by the fact that a concentration of hard materials in at least one first surface area (24) of the coating (22), which is intended to be contacted with the brake pad (14) during operation, has a value that changes continuously in the radial direction (R).

4. Brake disc (12) according to claim 3, characterized by the fact that the concentration of hard materials in the coating (22) first increases and then decreases with increasing radial distance from a central axis (30) of the brake disc (12).

5. Brake disc (12) according to claim 3 or 4, characterized by the fact that The concentration of hard materials in the coating (22) follows a Gaussian curve in the radial direction (R).

6. Brake disc (12) according to one of the preceding claims, characterized by the fact that the coating (22) is applied to the base body (20) by means of laser cladding or cold gas spraying.

7. Motor vehicle with a brake disc (12) according to one of the preceding claims.

8. Method for manufacturing a brake disc (12) for a motor vehicle, comprising a base body (20) made of a grey cast iron alloy and a coating (22), wherein, for manufacturing the brake disc (12), the coating (22) is applied to the base body (20) with different concentrations of hard materials in different areas.

9. Method according to claim 8, characterized by the fact that For the application of the coating (22), a powder is applied to the base body (20), wherein the powder applied to the base body (20) has a different concentration of hard materials in different areas.

10. Method according to claim 9, characterized by the fact that the powder is applied in a spiral pattern to the base body (20).

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