Brake disc and method for manufacturing the same

Abstract

The invention relates to a brake disc (3) having a heat-conducting layer (4, 6) with a thermal conductivity and a specific thermal resistance that can be set gradually, wherein the heat-conducting layer is composed of at least two different materials or different layer thicknesses, whereby the thermal conductivity or the specific thermal resistance is set gradually in the heat-conducting layer.

Description

Technical Field

[0001] The invention relates to the fields of vehicle technology and industrial plant technology and to a brake disc having at least one heat-conducting layer with a graded thermal conductivity and specific thermal resistance. The invention also relates to a method for producing a brake disc according to the invention. The proposed brake disc can be used, for example, as an internally ventilated brake disc in a vehicle or as a brake disc in an industrial brake or wind turbine. Background Art

[0002] Conventional brake disks in vehicles and industrial plants are either designed as one-piece brake disks made of one metal or ceramic material or as composite brake disks or multi-piece brake disks made of one or more metal or ceramic materials.

[0003] In motor vehicles, brake disks are attached to the rotating front and rear axles and, for this purpose, have planar contact surfaces which are in contact with the wheel rim on the one hand and with the wheel bearing on the other hand.

[0004] The brake disk also has a region which comprises a friction surface, via which the braking effect is achieved in cooperation with the brake lining.

[0005] In order to better dissipate the heat generated, the brake disc can be designed as an internally ventilated disc brake, for example. For this purpose, the brake disc has suitable ventilation channels on the inner side of the brake disc hub, which on the one hand draw in air, which flows through the brake disc and dissipates the heat generated in the brake disc and thus ensures cooling of the brake unit.

[0006] In order to better prevent the brake disc from wear and corrosion, various solutions are proposed in the prior art.

[0007] DE 10 2008 053 ​​637 A1 discloses a friction ring for a brake disk, which has a coating at least in certain areas, wherein the coating has a thickness profile with different coating thicknesses. The coating is applied by a thermal spraying process or a PVD process.

[0008] DE 10 2005 008 569 A1 discloses a method for producing a friction element, wherein a friction element base body is provided and a coating is applied. The coating comprises a molten alloy which is melted in a thermal production method.

[0009] WO 2007 / 043 961 A1 discloses a coated vehicle component which is essentially made of a metal-based material and comprises at least one working surface which is arranged such that it causes friction wear in a relative movement with 5 times the motion and comprises a wear-resistant coating. The component is characterized in particular by a top coating which comprises more than 50% by weight and less than 99% by weight of molybdenum, the remainder preferably being at least one element of the first group, the first group comprising aluminum, boron, carbon, chromium, cobalt, lanthanum, manganese, nickel, niobium, oxygen, silicon, tantalum, tungsten, yttrium and common impurities.

[0010] DE 10 2014 006 064 A1 discloses a component comprising a grey cast iron substrate and at least one covering layer, wherein a surface layer is formed directly on the grey cast iron substrate between the substrate and the covering layer, the surface layer comprising a layer containing nitrides, carbides and / or oxides. The covering layer consists of a cermet material of a metal matrix and an oxide ceramic component distributed therein, wherein the oxide ceramic component accounts for 30 to 70% by weight of the cermet material.

[0011] DE 10 2014 015 474 A1 discloses a brake disk having a gray cast iron substrate, the substrate having a plurality of surface layers arranged at least on the friction surface, wherein the surface layers on the gray cast iron substrate have, in order from the substrate to the outer surface: at least one bonding layer; an anti-corrosion layer made of a nitrided, oxidized, or nitrocarburized bonding layer material and optionally a gray cast iron material; an optional oxide layer made essentially of iron oxide; and an anti-wear layer or friction layer made of an oxide ceramic or cermet material. The bonding layer consists of the material of the gray cast iron substrate, wherein the Cr and / or Mo content is increased to 20 to 60% by weight, wherein a majority of the layered carbides of the gray cast iron are present in the bonding layer in a chemically bonded manner as chromium carbides and / or molybdenum carbides.

[0012] With the known solution, different coatings of the metal base body, which consists essentially of grey cast iron, are provided, which coatings are able to better protect the brake disk against corrosion and wear.

[0013] However, a disadvantage is that, especially in the case of brakes, which are becoming increasingly important in electric vehicles that use regeneration for energy recovery, the necessary operating temperatures cannot be achieved when the brake disc and brake lining interact, because the frequency of use of the brake system is greatly reduced due to the energy conversion. This can lead to a decrease in braking performance or even complete failure of the entire brake system.

[0014] A disadvantage of the prior art is also that, since the various proposed brake disk coatings are essentially embodied as hard material layers, a suitable material combination of the brake lining interacting with the brake disk must be adapted to the existing coating of the brake disk in a cost-intensive and time-consuming manner.

[0015] A disadvantage is also that, in the brake disc, due to the different introduction of heat, stresses are generated within the brake disc, which are generated due to temperature peaks in certain areas of the friction surface. This disadvantageously leads to warping of the brake disc (also called shielding effect or coning), which in turn leads to crack formation, especially in the uppermost hard material layer. Summary of the invention

[0016] The object of the present invention is to provide a new type of brake disc which eliminates the disadvantages of the prior art.

[0017] This object is achieved by the invention as specified in the claims. Advantageous embodiments are the subject matter of the dependent claims, wherein the invention also includes the individual dependent claims and their associated combinations, as long as they are not mutually exclusive.

[0018] The object according to the invention is achieved by a brake disc, which has a metal base body, the metal base body has at least one annular fixing element for fixing the brake disc to a rotating shaft, a first friction area facing the rotating shaft and configured as a circular surface, and a second friction area diametrically opposite to the first friction area and arranged away from the rotating shaft, the metal base body having at least one annular heat-conducting layer in the area of ​​the first and second friction areas, on which at least one hard material layer capable of withstanding friction stress is arranged, wherein by means of laser build-up welding, at least one heat-conducting layer is arranged on the metal base body and the hard material layer capable of withstanding friction stress is arranged on the heat-conducting layer, so that a material connection of the layers can be achieved, wherein the heat-conducting layer is composed of at least two different materials and the thermal conductivity λ in the heat-conducting layer is set gradually, wherein at least in the inner circumferential area of ​​the first and / or second friction area, a metal or ceramic material and / or a metal alloy with a thermal conductivity λ1 is present, and in the outer circumferential area of ​​the first and / or second friction area, a metal or ceramic material and / or a metal alloy with a thermal conductivity λ2 is present, wherein at least λ1<λ<λ2.

[0019] The object according to the invention is also achieved by a brake disk, which has a metal base body, which has at least one annular fixing element for fixing the brake disk to a rotating shaft, a first friction area facing the rotating shaft and configured as a circular surface, and a second friction area diametrically opposite the first friction area and arranged facing away from the rotating shaft, wherein the metal base body has at least one annular heat-conducting layer in the region of the first and / or second friction area, on which at least one hard material layer capable of withstanding friction stress is arranged, wherein the at least one heat-conducting layer is arranged on the metal base body and the hard material layer capable of withstanding friction stress is arranged on the heat-conducting layer by means of laser build-up welding, so that a material connection of the layers is achieved, and wherein at least one of the heat-conducting layers has a gradual layer thickness d in the radial direction toward the outer circumference of the brake disk.sw , thus the specific thermal resistance R in the thermal conductive layer thi It tapers gradually in the radial direction towards the outer circumference of the brake disk.

[0020] At least two heat conducting layers are advantageously arranged, a first heat conducting layer being arranged on the metal substrate and a second heat conducting layer being arranged on the first heat conducting layer, wherein at least the second heat conducting layer respectively forms an interface region with the frictionally stress-resistant hard material layer and with the first heat conducting layer.

[0021] In another advantageous design of the brake disc, at least one heat conducting layer and / or a hard material layer capable of withstanding frictional stress on the friction area facing the rotating shaft has different layer thicknesses than at least one heat conducting layer and / or a hard material layer capable of withstanding stress on the friction area facing away from the rotating shaft.

[0022] It is also advantageous if, in a radial direction toward the outer circumference of the brake disk, at least one heat-conducting layer comprises a material having a thermal conductivity λ1 of 10 W / (m*K) to 14 W / (m*K) in an inner circumferential region extending to a maximum of 40% of the circumferential surface, a material having a thermal conductivity λ2 of 12 W / (m*K) to 26 W / (m*K) in an intermediate circumferential region extending from 30% to a maximum of 65% of the circumferential surface, and a material having a thermal conductivity λ3 of 24 W / (m*K) to 40 W / (m*K) in an outer circumferential region extending from 60% of the circumferential surface to the outer circumference.

[0023] It is also advantageous if the at least one heat-conducting layer has a layer thickness d t which increases continuously or abruptly in the radial direction towards the outer circumference of the brake disk. sw .

[0024] Advantageously, the at least one heat conducting layer has a layer thickness d of 50 μm to 500 μm. swi , particularly advantageously with a layer thickness d of 100 μm to 150 μm swi .

[0025] It is also advantageous if, in the radial direction towards the outer circumference of the brake disk, the heat-conducting layer has a layer thickness d t t in an inner circumferential region extending up to a maximum of 40% of the circumferential surface than in an outer circumferential region. sw3 10%-15% larger layer thickness d sw1 and has a layer thickness d in the middle circumferential region extending from 30% to a maximum of 65% of the circumferential surface than in the outer circumferential region. sw3 5%-10% larger layer thickness d sw2 , wherein the outer circumferential region extends from 60% of the circumferential surface to the outer circumference, wherein the layer composition of the heat conducting layer and the hard material layer capable of withstanding frictional stresses is constant.

[0026] Advantageously, the heat conducting layer is made of an Al-based, Fe-based, Ni-based, Cr-based and / or Cu-based alloy.

[0027] Likewise advantageously, at least the heat conducting layer also comprises hard material particles of carbides and / or oxide ceramics, wherein advantageously the hard material particles of the heat conducting layer have an average particle size D of 0.5 μm to 120 μm. 50 , and wherein the volume proportion of the hard material particles in the heat conducting layer is also advantageously 1% to 80%, particularly advantageously 30% to 50%.

[0028] In an advantageous embodiment of the brake disk, the heat conducting layer is an alloy, wherein the minimum thermal conductivity in the axial direction is in a radial partial region and in the interface region with a hard material layer that can withstand frictional stresses, and the maximum thermal conductivity is in the interface region with another heat conducting layer or a metal matrix.

[0029] Advantageously, an adhesive layer is present at least between the metal base body and at least the first heat-conducting layer.

[0030] Advantageously, the hard material layer capable of withstanding frictional stresses has a layer thickness d of at least 50 μm to 500 μm. SH , a layer thickness d of 200 μm to 250 μm is particularly advantageous SH .

[0031] The hard material layer capable of withstanding frictional stresses is made of metal ceramics, particularly advantageously of silicon carbide, boron carbide, tungsten carbide, vanadium carbide, titanium carbide, tantalum carbide, chromium carbide and / or oxide ceramics, and very particularly advantageously of tungsten carbide with a stainless steel matrix from material group 4 or 5 having a Ni content ≤15 wt%.

[0032] The object of the present invention is also achieved by a method for manufacturing a brake disc claimed in accordance with the present invention, wherein a first heat conducting layer is at least partially materially connected to a metal substrate by means of laser build-up welding, and then a hard material layer capable of withstanding friction stress is materially connected to the first heat conducting layer, wherein the heat conducting layer is made of at least two different materials and the thermal conductivity λ1 is gradually set within the heat conducting layer so that the heat conducting layer has a gradually increasing thermal conductivity λ in the radial direction, wherein a metal or ceramic material and / or a metal alloy with a thermal conductivity λ1 is arranged at least in the inner circumferential region of the first and / or second friction region and a metal or ceramic material and / or a metal alloy with a thermal conductivity λ2 is arranged in the outer circumferential region of the first and / or second friction region, and finally the surface of the hard material layer capable of withstanding friction stress is processed.

[0033] Furthermore, according to the invention, a first heat conducting layer is at least partially materially connected to the metal substrate by means of laser deposition welding, and then a hard material layer capable of withstanding friction stress is materially connected to the first heat conducting layer, thereby achieving a material connection of the layers, wherein at least one heat conducting layer is deposited in a radial direction toward the outer circumference of the brake disk with a gradual layer thickness d sw arrangement, whereby the specific thermal resistance R thi It tapers gradually in the radial direction towards the outer circumference of the brake disk.

[0034] In an advantageous embodiment of the method, in a first step, the heat conducting layer has a layer thickness d in the radial direction in an inner circumferential region extending up to a maximum of 35% of the circumferential surface than in an outer circumferential region. s3 10%-15% larger layer thickness d s1 and has a layer thickness d in the middle circumferential region extending from 30% to a maximum of 65% of the circumferential surface than in the outer circumferential region. s3 5%-10% larger layer thickness d s2 , wherein the outer circumferential region extends from 60% of the circumferential surface of the brake disc to the outer circumference, so that the specific thermal resistance R in the heat conductive layer thi It gradually decreases from the inner circumferential area to the outer circumferential area.

[0035] Advantageously, in the radial direction towards the outer circumference of the brake disk, at least one heat conducting layer comprises a material with a thermal conductivity λ1 of 10 W / (m*K) to 14 W / (m*K) in an inner circumferential region extending to a maximum of 35% of the circumferential surface, a material with a thermal conductivity λ2 of 12 W / (m*K) to 26 W / (m*K) in an intermediate circumferential region extending from 30% to a maximum of 65% of the circumferential surface, and a material with a thermal conductivity λ3 of 24 W / (m*K) to 40 W / (m*K) is arranged in an outer circumferential region extending from 60% of the circumferential surface to the outer circumference of the circumferential surface.

[0036] It is particularly advantageous if the base body is heated to a temperature of 150° C. to 500° C. at least in a subregion of the first and / or second friction region before the heat conducting layer is applied by means of laser build-up welding.

[0037] With the solution according to the invention, a novel brake disc is provided, with which the thermal balance is controlled in an effective manner, in particular over the entire brake disc, and a uniform temperature distribution in the brake disc is achieved with improved braking performance. In addition, thermal stresses and crack formation are effectively avoided in a simple manner with the novel brake disc, wherein the heat introduction into the brake disc is distributed uniformly and the temperature distribution in the brake disc is regulated. The brake disc of the novel design can be used in industrial plants, wind turbines and in particular in vehicles, wherein vehicles are not to be understood only as passenger cars, but also as trucks, mopeds and bicycles.

[0038] The brake disc according to the present invention has a metal base body, which has an annular fixing element for fixing the brake disc to a rotating shaft, a first friction area facing the rotating shaft and configured as a circular surface, and a second friction area diametrically opposite to the first friction area and arranged away from the rotating shaft and also configured as a circular surface. The brake disc also has at least one heat-conducting layer configured according to the present invention and a hard material layer arranged on the heat-conducting layer that can withstand friction stress on the first and / or second friction area.

[0039] A typical temperature profile occurs during the braking process.

[0040] It has been found that an annular fastening element for fastening the brake disk to the rotating shaft has significantly less thermal load than the first and second friction regions of the metal basic body.

[0041] The low thermal load on the annular fixing element is caused by the material of the metal base body, which, like the metal base body, is usually made of, for example, grey cast iron and therefore has a high thermal conductivity λ in the range of approximately 50 W / (m*K).

[0042] In contrast, the temperature is always higher, in particular in the outer circumferential region of the first and second friction regions, than in the inner circumferential region of the friction disk, since the friction heat generated in the inner circumferential region is dissipated directly to the contacting and adjacently arranged annular fastening element.

[0043] It has been found that the second friction region facing away from the axis of rotation has a higher temperature during the braking process than the first friction region arranged diametrically opposite. Surprisingly, it has been found that the temperature difference occurring between the first and second friction region disadvantageously leads to a warping of the brake disk due to the temperature gradient (shielding effect, coning), a corrugated deformation of the surface of the hard material layer, and thus crack formation in the hard material layer that can withstand frictional stresses.

[0044] In order to achieve uniform heat distribution and load as well as a compensated thermal balance of the hard material layer capable of withstanding friction stress and the entire brake disc, it is proposed according to the present invention that at least one specially constructed heat-conducting layer is arranged between the metal matrix and the hard material layer capable of withstanding friction stress, and the heat-conducting layer has a gradually changing thermal conductivity λ in the radial direction from the annular fixing element to the outer circumference of the brake disc. i and the gradient specific thermal resistance R thi .

[0045] According to the invention, this is achieved in that at least one heat-conducting layer is composed of at least two different materials, the at least two different materials having different thermal conductivities. i The heat conducting layer is set gradually, wherein at least in the inner circumferential region of the first and / or second friction region, a metal or ceramic material and / or a metal alloy with a thermal conductivity λ1 is present. In the outer circumferential region of the first and / or second friction region, a metal or ceramic material and / or a metal alloy with a thermal conductivity λ2 is present. In principle, when selecting the material of the heat conducting layer, it is applicable that the thermal conductivity λ1 in the inner circumferential region in the radial direction of the brake disc is always smaller than the thermal conductivity λ2 in the outer circumferential region. In this regard, according to the invention, λ1<λ<λ2.

[0046] By different selections of the metal or ceramic material and / or metal alloy in the heat-conducting layer, the braking heat generated in the inner circumferential region of the brake disc is discharged with a delay via the region with low thermal conductivity λ1, which allows the brake disc to be more quickly controlled in temperature in this region and to be ready for use. In contrast, the braking heat generated in the outer circumferential region of the brake disc is quickly discharged from the frictionally stress-bearing hard material layer into the metal matrix via the material with high thermal conductivity λ2, which allows the frictionally stress-bearing hard material layer to cool quickly and improves the service life of the brake disc, in particular by preventing thermal peak loads in the outer circumferential region.

[0047] In order to achieve rapid readiness of the brake system for use, in particular in vehicles which use recuperated braking energy and the associated reduced number of braking operations, the corresponding heat-conducting layer can also have several different material regions at least in the radial direction toward the outer circumference of the brake disk, the thermal conductivity λ of the different material regions being different. i different.

[0048] Due to the different materials and thus different thermal conductivities λ1, λ2, ...λ i A continuous or sudden thermal conductivity gradient is achieved in the heat conducting layer.

[0049] Since the thermal conductivity λ1 of at least one of the materials of the heat-conducting layer disposed in the inner circumferential region of the first and / or second friction region is low, the friction heat generated in the hard material layer that can withstand friction stress and the heat-conducting layer is stored in this special inner circumferential region. As a result, the operating temperature of the brake disc is reached more quickly in the relevant inner circumferential region of the hard material layer due to an insulating effect and a faster operating temperature of the brake disc is achieved.

[0050] The temperature gradient between the inner circumferential region and the outer circumferential region in brake disks, in particular in hard material layers that can withstand frictional stresses, is usually caused by the different settings of the thermal conductivity λ in the heat-conducting layer. i And different settings of specific thermal resistance R thi The temperature in the brake disk is compensated and homogenized, thereby improving the service life and achieving a uniform braking effect over the entire surface of the hard material layer that can withstand frictional stresses.

[0051] In an advantageous embodiment of the invention, at least two heat-conducting layers can be arranged at least on the first and / or second friction region, wherein one heat-conducting layer is applied on the metal substrate and the other heat-conducting layer is applied on the previously arranged heat-conducting layer. The uppermost heat-conducting layer accordingly forms an interface with the hard material layer that can withstand friction stresses and with the heat-conducting layer arranged on the metal substrate.

[0052] It is important here that, in the case of several heat-conducting layers, at least the last heat-conducting layer which is materially connected to the hard material layer capable of withstanding frictional stresses has a thermal conductivity λ within the heat-conducting layer. i And therefore the specific thermal resistance R thi This means, in particular, that thermal loads occurring in the frictionally resistant hard material layer in the outer circumferential region during the braking process are avoided and that the generated braking heat is dissipated in a targeted manner from the outer circumferential region into the metal matrix, while in the inner circumferential region the heat is dissipated in a targeted and delayed manner and conducted in the frictionally resistant hard material layer to achieve an optimum operating temperature.

[0053] Advantageously, the heat conducting layer is constructed such that in the radial direction in an inner circumferential region extending to a maximum of 40% of the circumferential surface, a material having a thermal conductivity λ1 of 10 W / (m*K) to 14 W / (m*K); in an intermediate circumferential region extending from 30% to a maximum of 65% of the circumferential surface, a material having a thermal conductivity λ2 of 12 W / (m*K) to 26 W / (m*K); and in an outer circumferential region extending from 60% of the circumferential surface to the outer circumference, a material having a thermal conductivity λ3 of 24 W / (m*K) to 40 W / (m*K).

[0054] In this regard, at least one heat-conducting layer has different thermal conductivities λ in the first and / or second friction region. i , which takes into account the different temperatures during the braking process.

[0055] Particularly advantageous technical effects and effects are achieved by the coating method of laser build-up welding proposed according to the invention.

[0056] On the one hand, a material connection is established between the layers to be provided, namely the at least one heat-conducting layer and the hard material layer capable of withstanding frictional stresses, and between the at least one heat-conducting layer and the metal base body. This has the following advantages: better heat conduction between the layers and better connection of the layers to one another are achieved. Also, better protection against corrosion and wear is achieved.

[0057] Furthermore, in particular by means of the laser deposition welding proposed according to the invention, the thermal conductivity λ of the heat conducting layer to be set can be achieved in a simple manner. i and the specific thermal resistance R to be set thi This allows, in particular, the thermal conductivity to be set continuously or abruptly in a radial configuration relative to the circumference of the brake disc. By laser cladding, it is possible to combine different thermal conductivities λ during coating. i And specific thermal resistance R thi Different materials can be arranged continuously or discontinuously on the first and second friction areas in one manufacturing process. In addition, by laser cladding, the layer thickness d of each heat conducting layer on the brake disk can be changed. s and thus the specific thermal resistance R is set individually in a specific circumferential region of the brake disk. thi .

[0058] Al-based, Fe-based, Ni-based, Cu-based and / or Cr-based alloys as materials for the heat conducting layer according to the invention offer the following advantages: the thermal conductivity λ can be set continuously or abruptly at least in the radial and axial directions by means of the laser cladding method via the alloying elements or the composition of the metal or ceramic material. i And specific thermal resistance R thi .

[0059] The heat conducting layer is provided by laser deposition welding, so that the material composition, the specific thermal resistance R thi and thermal conductivity λ i , in order to provide a brake disc with a high thermal conductivity λ in a thermally highly loaded region of the first or second friction region of the brake disc, for example. i or low specific thermal resistance R thi The material has a high specific thermal resistance R and is arranged in an area with a low thermal load thi or low thermal conductivity λ i materials.

[0060] As a further option for thermal homogenization of the brake disk, it is proposed according to the invention to provide a heat-conducting layer made of only one material and having a layer thickness d sw The heat conduction layer is configured to gradually change in the radial direction toward the outer circumference of the brake disk, thereby reducing the specific thermal resistance R thi The desired temperature profiles of the first and second friction areas are set differently and thus adapted.

[0061] In a particularly preferred embodiment, the heat conducting layer has a layer thickness d in the radial direction in an inner circumferential region extending up to a maximum of 35% of the circumferential surface than in an outer circumferential region. sw3 10%-15% larger layer thickness d sw1 and has a layer thickness d in the middle circumferential region extending from 30% to a maximum of 65% of the circumferential surface than in the outer circumferential region. sw3 5%-10% larger layer thickness d sw2 , wherein the outer circumferential region extends from 60% of the circumferential surface to the outer circumference.

[0062] By providing different layer thicknesses d of at least one heat conducting layer sw In particular, the undesirable shielding effect, i.e. the deflection of the first and second friction areas and the associated warping of the entire brake disc caused by the formation of a corrugated shape in the hard material layer that can withstand friction stress, is overcome. thi The thermal balance in the friction disks is set individually.

[0063] In a further advantageous embodiment, the heat conducting layer additionally comprises hard material particles, which in the first and second friction regions bring about a better strength and hardness of the heat conducting layer and the layer structure. The hard material particles particularly advantageously have an average particle size D of 0.5 μm to 120 μm. 50 Furthermore, it can be present in a volume fraction of 1% to 80%, particularly advantageously between 30% and 50%.

[0064] Advantageously, a brake disc is provided in which an adhesion layer is present at least between the metal substrate and at least one heat-conducting layer. The hard layer brings about a better connection of the first heat-conducting layer to the metal substrate, so that mechanical preparation of the surface of the metal substrate can be dispensed with. It is also possible to provide an adhesion layer between the heat-conducting layers and / or between the heat-conducting layer and the layer of hard material that can withstand frictional stresses, in order to improve the adhesion of the individual layers to one another and the adhesion strength of the entire layer structure.

[0065] For cost-effective production and a long service life of the brake disk, it is advantageous if the hard material layer capable of withstanding frictional stresses has at least a layer thickness d of 50 μm to 500 μm. SH , very particularly advantageously with a layer thickness d of 200 μm to 250 μmSH It has been found to be particularly advantageous here if the hard material layer capable of withstanding frictional stresses is made of a metal ceramic, for example of silicon carbide, boron carbide, tungsten carbide, vanadium carbide, titanium carbide, tantalum carbide, chromium carbide and / or oxide ceramics, particularly advantageously of tungsten carbide in a stainless steel matrix of material group 4 or 5 with a Ni content ≤15 wt %.

[0066] It has been found that when the heat-conducting layer is arranged on the metal substrate, a thermally induced warping of the friction region occurs, which results in the aforementioned shielding effect. In contrast, it is advantageously provided that before the heat-conducting layer is arranged in a material connection by means of laser build-up welding, the metal substrate is heated to a temperature of 150° C. to 500° C. in a preceding heat treatment process at least in a subregion of the first and / or second friction region. As a result, the thermally induced stresses in the brake disc can be minimized. In addition, a better material connection between the heat-conducting layer and the metal substrate is achieved. Furthermore, by preheating the metal substrate, the laser intensity during laser build-up welding can be reduced, which in turn advantageously allows the carbides to be integrated in the hard material layer without damage. Lasers with lower laser power result in lower production costs.

[0067] With the implementation according to the invention, a novel brake disk is provided, with which a number of technical advantages and effects are achieved.

[0068] At least one heat-conducting layer on the first and / or second friction region of the metal base body has different materials or only one material with different layer thicknesses, which differ in their thermal conductivity and / or in their specific thermal resistance and thus achieve a thermal influence on individual regions of the brake disk. Here, the different materials or different layer thicknesses of at least one heat-conducting layer are set gradually, so that the thermal conductivity increases continuously or abruptly in the radial direction at least toward the outer circumference of the brake disk or the specific thermal resistance decreases continuously or abruptly in the radial direction at least toward the outer circumference of the brake disk. This provides the following advantages:

[0069] - Targeted avoidance of thermal load peaks in individual areas of the brake disc;

[0070] - Setting a uniform temperature distribution in the brake disc;

[0071] -Prevents brake disc warping and crack formation;

[0072] - Provides faster deployment and braking performance; and

[0073] - Achieve a longer service life of the brake disc. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention is explained in more detail below based on three embodiments.

[0075] In the attached picture:

[0076] Figure 1 shows a schematic cross-section through a brake disc;

[0077] Figure 2 Details of the first and second friction areas are shown;

[0078] Figure 3 A schematic diagram of a coating of a brake disk is shown, the coating having a heat-conducting layer with a constant layer thickness and a graded material composition and a hard material layer capable of withstanding friction stresses;

[0079] Figure 4 shows an axial top view of a brake disc having inner, middle and outer circumferential regions with a graded heat conducting layer;

[0080] Figure 5 shows a schematic layer structure of a heat conducting layer with a graded layer thickness and a hard material layer capable of withstanding friction stresses;

[0081] Figure 6 shows a schematic layer structure with a combination of a heat conducting layer with a graded layer thickness and a heat conducting layer of a graded material and a hard material layer capable of withstanding friction stresses; and

[0082] Figure 7 A schematic layer structure with two thermally graded layers arranged one above the other is shown. DETAILED DESCRIPTION

[0083] Example 1

[0084] Figure 1 and Figure 2 The schematic cross section through a brake disk is shown having a metal base body 1 made of grey cast iron, a fastening element 12 , heat conducting layers 4 , 6 arranged diametrically on both sides of the metal base body 1 , and a hard material layer 8 which can withstand frictional stresses.

[0085] The first heat conducting layer 4 ( Figure 3 ) consists of an Fe-based alloy and a first heat conducting layer 6 facing away from the rotation axis 14 consists of a Ni-based alloy, wherein the heat conducting layers 4 and 6 applied by means of laser build-up welding are arranged on a metal base body 1 consisting of gray cast iron.

[0086] A hard material layer 8 capable of withstanding frictional stress is arranged on the respective heat conducting layers 4 and 6. The hard material layer 8 is made of tungsten carbide and has a stainless steel matrix with material number DIN EN 1.4016 (430L) and an average layer thickness of 120 μm. The hard material layer 8 has a thermal conductivity λ of 78 W / (m*K).

[0087] Figure 4The diagram shows a plan view of a brake disk, which has two diametrically opposite heat-conducting layers 4 and 6 , namely a first heat-conducting layer 4 facing the axis of rotation and a heat-conducting layer 6 facing away from the axis of rotation 14 .

[0088] The first heat-conducting layer 4 facing the rotating shaft 14 has a total of three circumferential regions 9, 10 and 11 in the radial direction, and the three circumferential regions have different materials. The first material of the heat-conducting layer 4 has a thermal conductivity λ1 of 10W / (m*K) in the inner circumferential region 9 in the radial direction, and the inner circumferential region 9 includes 35% of the circumferential surface of the friction region; the second material has a thermal conductivity λ2 of 25W / (m*K) in the middle circumferential region 10 in the radial direction, and the middle circumferential region 10 includes 35% to 60% of the circumferential surface of the friction region; and the third material has a thermal conductivity λ3 of 55W / (m*K) in the outer circumferential region 11 in the radial direction, and the outer circumferential region 11 includes 60% of the circumferential surface of the friction region up to the outer circumference.

[0089] The heat conducting layer 6 facing away from the rotation axis 14 also has a total of three circumferential regions 9, 10 and 11 in the radial direction, which have different materials. The first material of the heat conducting layer 6 facing away from the rotation axis 14 has a thermal conductivity λ1 of 12 W / (m*K) in the inner circumferential region 9 in the radial direction, which includes 30% of the circumferential surface of the friction region; the second material has a thermal conductivity λ2 of 23 W / (m*K) in the middle circumferential region 10 in the radial direction, which includes 30% to 45% of the circumferential surface of the friction region; and the third material has a thermal conductivity λ3 of 48 W / (m*K) in the outer circumferential region 11 in the radial direction, which includes 45% of the circumferential surface of the friction region up to the outer circumference.

[0090] like Figure 3 and Figure 6 As shown in FIG. 1 , the first heat conducting layer 4 facing the rotation axis 14 has a layer thickness d which decreases continuously in the radial direction. sw , where the minimum layer thickness d on the outer circumference of the friction zone sw3 The maximum layer thickness d is 90 μm and on the inner circumference of the friction zone sw4 It is 145μm.

[0091] like Figure 3 and Figure 6 As shown in FIG. 1 , the heat conducting layer 6 facing away from the rotation axis 14 has a constant layer thickness d in the radial direction. sw , the layer thickness is 120 μm.

[0092] The provided heat-conducting layers 4 and 6 achieve a uniform thermal balance in the hard material layer 1 that can withstand frictional stresses, by means of which a faster thermal readiness is achieved over the entire circumference of the friction regions 2 and 3. In addition, the graduated heat-conducting layers 4 and 6 and the different layer thicknesses prevent the occurrence of a shielding effect, thereby preventing the formation of cracks in the brake disk.

[0093] Example 2

[0094] Figure 1 and Figure 2 The schematic cross section through a brake disk is shown having a metal base body 1 made of grey cast iron, a fastening element 12 , heat conducting layers 4 and 6 arranged diametrically on both sides of the metal base body, and a hard material layer 8 which can withstand frictional stresses.

[0095] The first heat conducting layer 4 ( Figure 3 ) is made of a Cr-based alloy and the heat conducting layer facing away from the rotation axis 14 is made of a Cu-based alloy, wherein the heat conducting layers 4 and 6 are arranged on the metal base body 1 made of gray cast iron by means of laser build-up welding.

[0096] A friction-resistant hard material layer 8 made of tungsten carbide is arranged on the respective heat conducting layers 4 and 6 . The hard material layer 8 has a stainless steel matrix with material number DIN EN 1.4016 (430L) and an average layer thickness of 120 μm. The hard material layer 8 has a thermal conductivity λ of 78 W / (m*K).

[0097] exist Figure 4 , a top view of a brake disk is shown, wherein the brake disk has two diametrically opposite heat-conducting layers, namely a heat-conducting layer 4 facing the rotation axis 14 and a heat-conducting layer 6 facing away from the rotation axis 14 .

[0098] The heat-conducting layer 4 facing the rotating shaft 14 has a total of three regions 9, 10 and 11 in the radial direction, and the three regions have different materials. The first material of the heat-conducting layer 4 has a thermal conductivity λ1 of 12W / (m*K) in the inner circumferential region 9 in the radial direction, and the inner circumferential region 9 includes 35% of the circumferential surface of the friction area; the second material of the heat-conducting layer has a thermal conductivity λ2 of 23W / (m*K) in the middle circumferential region 10 in the radial direction, and the middle circumferential region 10 includes 40% of the circumferential surface of the friction area; and the third material of the heat-conducting layer has a thermal conductivity λ3 of 36W / (m*K) in the outer circumferential region 11 in the radial direction, and the outer circumferential region 11 includes 30% of the circumferential surface of the friction area.

[0099] The heat conducting layer 6 facing away from the rotation axis 14 also has a total of three regions 9, 10 and 11 in the radial direction, which have different materials. The first material of the heat conducting layer has a thermal conductivity λ1 of 12 W / (m*K) in the inner circumferential region 9 in the radial direction, and the inner circumferential region 9 includes 30% of the circumferential surface of the friction region; the second material of the heat conducting layer has a thermal conductivity λ2 of 23 W / (m*K) in the radial direction in the middle circumferential region, and the middle circumferential region includes 40% of the circumferential surface of the friction region; and the third material of the heat conducting layer has a thermal conductivity λ3 of 36 W / (m*K) in the radial direction in the outer circumferential region 11, and the outer circumferential region 11 includes 30% of the circumferential surface of the friction region.

[0100] according to Figure 5 The heat conducting layer 6 facing away from the rotation axis 14 and the heat conducting layer 4 facing the rotation axis 14 have a layer thickness d which decreases continuously in the radial direction. sw , where the minimum layer thickness d on the outer circumference of the friction zone sw1 and d sw3 The maximum layer thickness d is 80 μm and on the inner circumference of the friction area sw2 and d sw4 is 160μm.

[0101] The provided heat-conducting layers 4 and 6 achieve a uniform thermal balance in the hard material layer 7 that can withstand frictional stresses, by means of which a faster thermal readiness is achieved over the entire circumference of the friction regions 2 and 3. Furthermore, the graduated heat-conducting layers 4 and 6 and the different layer thicknesses prevent the occurrence of a shielding effect, thereby preventing the formation of cracks in the brake disk.

[0102] Example 3

[0103] Figure 7 A first friction region 2 or a second friction region 3 is shown, in which two different heat-conducting layers 4 and 5 as well as a hard material layer 8 which can withstand frictional stresses are arranged on a metal base body 1 .

[0104] A heat conducting layer 5 made of an Al-based alloy without a gradient is arranged on the metal substrate 1. A heat conducting layer 4 is arranged on the heat conducting layer 5 and is made of a Cu-based alloy.

[0105] The heat conducting layer 5 has a total of three regions 9, 10 and 11 in the radial direction, and the three regions have different materials. The first material of the heat conducting layer has a thermal conductivity λ1 of 12 W / (m*K) in the inner circumferential region 9 in the radial direction, and the inner circumferential region 9 includes 30% of the circumferential surface of the friction region; the second material of the heat conducting layer has a thermal conductivity λ2 of 23 W / (m*K) in the middle circumferential region 10 in the radial direction, and the middle circumferential region 10 includes 40% of the circumferential surface of the friction region; and the third material of the heat conducting layer has a thermal conductivity λ3 of 36 W / (m*K) in the outer circumferential region 11 in the radial direction, and the outer circumferential region 11 includes 30% of the circumferential surface of the friction region.

[0106] The heat conducting layer 5 has an average layer thickness d in the radial direction. sw A constant layer height of 120 μm.

[0107] The provided heat-conducting layers 4 and 5 achieve a uniform thermal balance in the hard material layer 1 that can withstand frictional stresses, by means of which a faster thermal readiness is achieved over the entire circumference of the friction regions 2 and 3. In addition, the graduated heat-conducting layers 4 and 5 and the different layer thicknesses prevent the occurrence of a shielding effect, thereby preventing the formation of cracks in the brake disk.

[0108] Reference numerals list

[0109] 1-Metal substrate

[0110] 2- First friction area facing the rotating axis

[0111] 3- Second friction area facing away from the axis of rotation

[0112] 4- The first heat conducting layer facing the rotating axis

[0113] 5- The second heat conducting layer facing the rotating axis

[0114] 6-The first heat-conducting layer facing away from the rotation axis

[0115] 7- The second heat-conducting layer facing away from the rotation axis

[0116] 8-Hard material layer that can withstand friction stress

[0117] 9-Inner Circumference Area

[0118] 10-Middle circumference area

[0119] 11-Outer circumference area

[0120] 12-Fixed elements

[0121] 13- Ventilation channel

[0122] 14- Rotation axis.

Claims

1. A brake disc, comprising a metal base body (1), the metal base body (1) having at least one annular fixing element (12) for fixing the brake disc to a rotating shaft (14), a first friction area (2) located axially inside and configured as a circular surface, and a second friction area (3) arranged axially opposite to the first friction area (2) and located axially outside, wherein the metal base body (1) has at least one annular heat-conducting layer (4, 6) in the region of the first and second friction areas (2, 3), at least one hard material layer (8) capable of withstanding friction stress is arranged on the heat-conducting layer (4, 6), wherein the at least one heat-conducting layer (4, 6) is welded to the heat-conducting layer by means of laser cladding. ) is arranged on the metal substrate (1) and the hard material layer (8) capable of withstanding friction stress is arranged on the heat-conducting layers (4, 6) so that material connection of these layers can be achieved, wherein the heat-conducting layers (4, 6) are composed of at least two different materials and the thermal conductivity λ in the heat-conducting layers (4, 6) is gradually set, wherein at least in the inner circumferential area (9) of the first and / or second friction area (2, 3), there is a metal or ceramic material and / or a metal alloy with a thermal conductivity λ1, and in the outer circumferential area (11) of the first and / or second friction area (2, 3), there is a metal or ceramic material and / or a metal alloy with a thermal conductivity λ2, wherein λ1<λ<λ2.

2. A brake disc, comprising a metal base body (1), the metal base body (1) having at least one annular fixing element (12) for fixing the brake disc to a rotating shaft (14), a first friction region (2) located axially inside and configured as a circular surface, and a second friction region (3) located opposite the first friction region (2) in the axial direction and located axially outside, wherein the metal base body (1) has at least one annular heat-conducting layer (4, 6) in the region of the first and / or second friction region (2, 3), on which at least one hard material layer (8) capable of withstanding friction stress is arranged, wherein the at least one heat-conducting layer (4, 6) is arranged on the metal base body (1) and the hard material layer (8) capable of withstanding friction stress is arranged on the heat-conducting layer (4, 6) by means of laser build-up welding, so that a material connection of these layers is achieved, and wherein at least one of the heat-conducting layers (4, 6) has a gradually varying layer thickness d in the radial direction toward the outer circumference of the brake disc. sw , thus, in the heat conducting layer (4, 6) the specific thermal resistance R thi The outer circumference of the brake disc gradually decreases in the radial direction.

3. The brake disc according to claim 1 or 2, wherein: At least two heat conducting layers are arranged, wherein a first heat conducting layer is arranged on the metal substrate and a second heat conducting layer is arranged on the first heat conducting layer, wherein at least the second heat conducting layer forms an interface region with the hard material layer capable of withstanding friction stress and with the first heat conducting layer, respectively.

4. The brake disc according to claim 1 or 2, wherein: The at least one heat conducting layer and / or the hard material layer capable of withstanding frictional stresses on the first friction region and the at least one heat conducting layer and / or the hard material layer capable of withstanding frictional stresses on the second friction region are formed with different layer thicknesses.

5. The brake disc according to claim 1 or 2, wherein: In the radial direction toward the outer circumference of the brake disk, at least one heat conducting layer has a material with a thermal conductivity λ1 of 10 W / (m*K) to 14 W / (m*K) in an inner circumferential region extending to a maximum of 40% of the circumferential surface, has a material with a thermal conductivity λ2 of 12 W / (m*K) to 26 W / (m*K) in an intermediate circumferential region extending from 30% to a maximum of 65% of the circumferential surface, and has a material with a thermal conductivity λ3 of 24 W / (m*K) to 40 W / (m*K) in an outer circumferential region extending from 60% of the circumferential surface to the outer circumference.

6. The brake disc according to claim 1 or 2, wherein: At least one heat-conducting layer has a layer thickness d which increases continuously or abruptly in the radial direction towards the outer circumference of the brake disk. sw .

7. The brake disc according to claim 1 or 2, wherein: The at least one heat conducting layer has a layer thickness d of 50 μm to 500 μm. swi .

8. The brake disc according to claim 1 or 2, wherein: The at least one heat conducting layer has a layer thickness d of 100 μm to 150 μm. swi .

9. The brake disc according to claim 2, wherein: In the radial direction towards the outer circumference of the brake disk, the heat conducting layer has a layer thickness d in an inner circumferential region extending up to a maximum of 40% of the circumferential surface than in an outer circumferential region. sw3 10%-15% larger layer thickness d sw1 and has a layer thickness d in the middle circumferential region extending from 30% to a maximum of 65% of the circumferential surface than in the outer circumferential region. sw3 5%-10% larger layer thickness d sw2 , wherein the outer circumferential region extends from 60% of the circumferential surface to the outer circumference, wherein the layer composition of the heat conducting layer and the hard material layer capable of withstanding frictional stresses is constant.

10. The brake disc according to claim 1 or 2, wherein: The heat conducting layer is made of Al-based, Fe-based, Ni-based, Cr-based and / or Cu-based alloy.

11. The brake disc according to claim 1 or 2, wherein: The heat conducting layer further comprises hard material particles of carbides and / or oxide ceramics.

12. The brake disc according to claim 11, wherein: The hard material particles of the heat conducting layer have an average particle size D of 0.5 μm to 120 μm. 50 .

13. The brake disc according to claim 11, wherein: The volume proportion of the hard material particles in the heat conducting layer is 1% to 80%.

14. The brake disc according to claim 11, wherein: The volume proportion of the hard material particles in the heat conducting layer is 30% to 50%.

15. The brake disc according to claim 1 or 2, wherein: The heat conducting layer is an alloy, wherein in the axial direction the minimum thermal conductivity is in a radial partial region and in an interface region with the frictionally stress-bearing hard material layer and the maximum thermal conductivity is in an interface region with another heat conducting layer or the metal matrix.

16. The brake disc according to claim 3, wherein: An adhesion layer is present at least between the metal substrate and the first heat conducting layer.

17. The brake disc according to claim 1 or 2, wherein: The hard material layer capable of withstanding frictional stresses has a layer thickness d of 50 μm to 500 μm. SH .

18. The brake disc according to claim 1 or 2, wherein: The hard material layer capable of withstanding frictional stresses has a layer thickness d of 200 μm to 250 μm. SH .

19. The brake disc according to claim 1 or 2, wherein: The hard material layer capable of bearing friction stress is made of metal ceramics.

20. The brake disc according to claim 1 or 2, wherein: The hard material layer capable of bearing friction stress is made of silicon carbide, boron carbide, tungsten carbide, vanadium carbide, titanium carbide, tantalum carbide, chromium carbide and / or oxide ceramics.

21. The brake disc according to claim 1 or 2, wherein: The hard material layer capable of withstanding frictional stress is made of tungsten carbide on a stainless steel matrix of material group 4 or 5 with a Ni content of ≤15 wt %.

22. A method for producing a brake disc according to any one of claims 1 to 8 and 10 to 21, wherein: By means of laser cladding, a first heat conducting layer (4, 6) is at least partially materially connected to a metal substrate (1), and then a hard material layer (8) capable of withstanding friction stress is materially connected to the first heat conducting layer (4, 6), wherein the heat conducting layer (4, 6) is made of at least two different materials and the thermal conductivity is gradually set in the heat conducting layer so that the heat conducting layer has a gradually increasing thermal conductivity λ in the radial direction, wherein at least a metal or ceramic material and / or a metal alloy with a thermal conductivity λ1 is arranged in an inner circumferential area (9) of the first and / or second friction area (2, 3) and a metal or ceramic material and / or a metal alloy with a thermal conductivity λ2 is arranged in an outer circumferential area (11) of the first and / or second friction area (2, 3), and finally the surface of the hard material layer (8) capable of withstanding friction stress is processed.

23. A method for producing a brake disc according to any one of claims 1 to 21, wherein: By means of laser cladding, a first heat conducting layer (4, 6) is at least partially materially connected to a metal substrate (1), and then a hard material layer (8) capable of withstanding friction stress is materially connected to the first heat conducting layer (4, 6), thereby achieving material connection of the layers (4, 6, 8), wherein at least one heat conducting layer (4, 6) is disposed in a radial direction toward the outer circumference of the brake disc with a gradually varying layer thickness d sw Arrangement, whereby the specific thermal resistance R thi The brake disc gradually decreases in radial direction toward the outer circumference.

24. The method according to claim 23, wherein: In a first step, in the radial direction, the heat conducting layer has in an inner circumferential region extending up to a maximum of 35% of the circumferential surface a layer thickness d t ... s3 10%-15% larger layer thickness d s1 and has a layer thickness d in the middle circumferential region extending from 30% to a maximum of 65% of the circumferential surface than in the outer circumferential region. s3 5%-10% larger layer thickness d s2 , wherein the outer circumferential region extends from 60% of the circumferential surface of the brake disc to the outer circumference, so that the specific thermal resistance R thi The thickness of the circumferential surface of the substrate decreases gradually from the inner circumferential region to the outer circumferential region.

25. The method according to any one of claims 22 to 24, wherein: In the radial direction toward the outer circumference of the brake disk, at least one heat conducting layer has a material with a thermal conductivity λ1 of 10 W / (m*K) to 14 W / (m*K) in an inner circumferential region extending to a maximum of 35% of the circumferential surface, has a material with a thermal conductivity λ2 of 12 W / (m*K) to 26 W / (m*K) in an intermediate circumferential region extending from 30% to a maximum of 65% of the circumferential surface, and has a material with a thermal conductivity λ3 of 24 W / (m*K) to 40 W / (m*K) in an outer circumferential region extending from 60% of the circumferential surface to the outer circumference.

26. The method according to any one of claims 22 to 24, wherein: Before the heat conducting layer is arranged by means of laser build-up welding, the metal base body is heated to a temperature of 150° C. to 500° C. at least in a subregion of the first and / or second friction region.

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