Brake pad with a layer of anisotropic material properties

Abstract

Brake pad for a vehicle brake, comprising a backing plate (1), a bottom layer (2) and a friction material (3) layered in this order in a z-direction, wherein the brake pad is configured to be moved in the z-direction in order to be pressed against a rotating body for braking purposes, wherein the sublayer (2) has an anisotropic material property, wherein at least one material parameter in the z-direction has a value that differs from its value in a direction orthogonal to the z-direction, wherein the sublayer comprises a base material (2.1) and insert elements (2.2) arranged in the base material (2.1), wherein at least some of the insert elements (2.2) are elongated elements (2.2a) oriented in a principal direction which deviates by no more than 30° from the z-direction, wherein a higher density of insert elements (2.2) is provided in a marginal area near the outer edges of the sublayer (2) than in a central area of ​​the sublayer (2), wherein the insert elements (2.2) in the marginal area frame the central area of ​​the sublayer (2).

Description

[0001] The invention lies in the field of mechanical engineering. It relates to vehicle technology, namely vehicle brakes.

[0002] The technique described in publication JP 2000-161 406 A aims to improve the coefficient of friction by forming a base layer capable of elastically deforming against a counter material on a carrier plate during the frictional sliding time. The base layer is formed by laminating a friction surface onto the base layer, which contains a fiber base material, a filler material, and a binder.

[0003] Publication JP 2000-027 912 A describes a friction material containing 15% or more by volume of iron fibers or powder and high-strength grains, 20% or more by volume of graphite powder or a comparable powdered material, as well as a binder and a friction regulating agent. The backplate is primarily made of iron, but other materials such as ceramics, fiber-reinforced materials, and the like may also be used. A heat-insulating material is used between the friction material and the backplate. This heat-insulating material contains 15% or more by volume of carbon to suppress thermal conductivity and 20% or more by volume of iron fibers or powder and grains to minimize the difference in thermal expansion with the friction material.

[0004] German patent application DE 36 17 846 A1 describes the manufacture of a brake shoe for disc brakes, consisting of a carrier plate, an intermediate layer, and a friction layer. The intermediate layer material and a heat-activated adhesive are mixed together. The mixture is applied in sheet form to a fiberglass mesh, spread evenly, and then dried.

[0005] The German publication DE 11 43 404 A relates to a disc brake for vehicles, in particular for motor vehicles, with a brake caliper encompassing the brake disc, in which brake pads mounted on a steel support plate are guided and held relative to the brake disc, wherein an intermediate layer cooperating with the brake disc is arranged between each brake pad and its associated steel support plate, the coefficient of friction of which is lower than that of the brake pad and which comes into frictional contact with the brake disc after the complete wear of the brake pad.

[0006] Document US 2013 / 0240304A1 describes a multi-layer brake pad assembly comprising a friction material layer, a heat-insulating material layer, and a backing plate. The heat-insulating material is a fiber-reinforced ceramic matrix composite with high fracture toughness and low thermal conductivity. It is positioned between the friction material and the backing plate and restricts the heat flow transferred from the backing plate to the hydraulic fluid during heavy braking, thereby minimizing the onset of braking losses due to hydraulic fluid evaporation caused by overheating.

[0007] The JP S61-140 632 A shows that a wire mesh is provided at the interface between a friction layer and a second layer in a brake pad.

[0008] JP 2013-19526A shows that a graphite plate is arranged between a friction material and a back plate.

[0009] DE 10 2011 051 061 A1 relates to a brake component, in particular for a brake shoe and / or for a brake, which has at least one viscoelastic layer. The brake component is characterized in that at least one side of the viscoelastic layer is positively and / or materially bonded to a stabilizing layer that incompletely covers the side of the viscoelastic layer.

[0010] DE 10 2018 216 346 A1 relates to a brake pad for a vehicle brake, wherein the brake pad comprises a friction lining having a leading edge and a rear edge at two opposite ends, a backing plate that holds the friction lining, and a backing layer arranged between the backing plate and the friction lining, the backing layer connecting the friction lining to the backing plate. A front section of the backing layer extending from a front side of the backing layer located below the leading edge of the friction lining and / or a rear section of the backing layer extending from a rear side of the backing layer located below the rear edge of the friction lining is made of a different material than the remaining part of the backing layer.

[0011] It is a priority for automakers to reduce fuel consumption and CO2 emissions. One aspect that can be improved in this regard is reducing brake drag. This means that while driving, when the brakes are not applied, a gap should be maintained between the brake disc and pads. This gap should be established as quickly as possible after releasing the brakes and then maintained. Solutions for reducing brake drag often have drawbacks regarding braking performance and / or pedal feel. Some solutions involve the use of special chamfers, seals, or sealing grooves.

[0012] One aspect to consider is that, due to the hyperplastic homogeneous behavior of the sealing material, the seal pushes the piston back towards the disc after the brakes are released.

[0013] In view of this, an objective of the invention is to reduce the drag torque and to enable the maintenance of a targeted gap between linings and disc surface.

[0014] This is achieved, for example, by a brake block according to claim 1 or by a brake block as described below. Advantageous embodiments are found in the dependent claims, in the following description, and in the figures.

[0015] According to this application, a brake pad for a vehicle brake comprises a backing plate, a base layer, and a friction material, layered in that order in a z-direction. The brake pad is designed to be moved in the z-direction to be pressed against a rotating body for braking purposes.

[0016] The sublayer exhibits an anisotropic material property, where at least one material parameter in the z-direction has a value that differs from its value in a direction orthogonal to the z-direction.

[0017] This type of anisotropic material property can facilitate brake pad retraction and / or the maintenance of a desired gap. In particular, the anisotropic material properties can be tuned so that the underlayer contracts in the z-direction as the brake system cools. Conversely, the brake pressure can increase when the brakes are applied because the underlayer expands under heat.

[0018] The anisotropic material property is given, for example, by - an anisotropic modulus of elasticity and / or - an anisotropic shear modulus and / or - an anisotropic Poisson number, and / or - anisotropic thermal conductivity, and / or - anisotropic thermal expansion, and / or - anisotropic compressibility, and / or - an anisotropic memory module and / or - an anisotropic loss modulus.

[0019] Within the scope of this invention, the sublayer comprises a base material and insert elements arranged within the base material. The insert elements are arranged such that the aforementioned anisotropic material property is achieved for the sublayer as a whole. For example, the selection of a material for the insert elements and their arrangement in specific sections of the sublayer and / or with a specific orientation leads to anisotropic properties of the entire sublayer, which comprises the base material and the insert elements. Specific configurations are listed below.

[0020] The insert elements can include, for example, rubber and / or minerals, such as stone, and / or glass and / or metal, such as steel, and / or phenol. The materials can be selected and combined to achieve specific material properties.

[0021] According to the invention, at least some of the insert elements are elongated elements, such as fibers or rods.

[0022] The elongated elements are aligned in a principal direction that deviates from the z-direction by a maximum of 30°. Certain orientations and / or arrangements in specific regions of the sublayer can cause or enhance anisotropy.

[0023] In one example, the elongated elements extend in the z-direction, i.e., they are arranged predominantly along the z-direction, which is the axial direction of the braking system.

[0024] At least some of the insert elements, e.g., the elongated elements, can have a diameter of at least 40 µm or at least 50 µm and / or at most 110 µm or at most 100 µm. Additionally or alternatively, they can have a length of at least 0.4 mm or at least 0.5 mm and / or at most 3 mm or at most 2 mm.

[0025] Additionally or alternatively, at least some of the insert elements can have a diameter of no more than 50 µm and / or a length of no more than 0.1 mm. In possible embodiments, these insert elements are aligned in a principal direction. It is also possible that they are not aligned in a principal direction.

[0026] More precisely, possible embodiments may include elongated elements with the aforementioned dimensions arranged along a principal direction, and may include additional smaller insert elements that are not oriented in any particular way. These smaller elements can be positioned in specific regions of the sublayer to contribute to a desired anisotropy.

[0027] According to the invention, a higher density of insert elements (referring to all types of insert elements, such as elongated insert elements, larger insert elements, or smaller insert elements) is provided in a peripheral region near the outer edges of the sublayer than in a central region of the sublayer. The insert elements in the peripheral region can then be considered as a frame for the central region of the sublayer. The central region can be free of insert elements or have a lower density of insert elements.

[0028] Additionally or alternatively, a higher density of insert elements can be provided in the immediate vicinity of a backplate.

[0029] For example, the edge region with the increased density of inlay elements can be limited to a distance of no more than 4 mm, 3 mm, or 2 mm from an outer edge of the substrate. Additionally or alternatively, the area near the backplate with the higher density of inlay elements can be limited to a distance of no more than 0.5 mm from the backplate. The remaining portion of the substrate, separated from the edge region at the edges and from the area near the backplate, can be free of inlay elements or have a lower density (e.g., bulk density and / or mass density) of inlay elements than the edge region and / or the area around the backplate.

[0030] For example, the distance between adjacent insert elements, especially elongated elements, is on average less than 0.5 mm, less than 0.3 mm, or less than 0.1 mm in the edge region. For example, at least some of the adjacent insert elements (such as the elongated elements) touch in the edge region.

[0031] For example, the coefficient of thermal expansion of the insert elements can be at least twice that of the base material. In a preferred optional embodiment, the coefficient of thermal expansion of the insert elements is at least three times that of the base material. The optional arrangement along the z-direction results in expansion predominantly in the z-direction, which can be a desirable effect.

[0032] For example, the material of the insert elements may have a thermal expansion of at least 1.0 E⁻¹ / K and / or at most 1.4 E⁻⁵ 1 / K when heated, and / or the base material may have a thermal expansion of at least 0.2 E⁻⁵ 1 / K and / or at most 0.4 E⁻⁵ 1 / K. Additionally or alternatively, the material of the insert elements may have a thermal contraction of at least -3 E⁻⁶ 1 / K and / or at most -5 E⁻⁶ 1 / K when cooling, and / or the base material may have a thermal contraction of at least -1.2 E⁻⁶ 1 / K and / or at most -1.6 E⁻⁶ 1 / K.

[0033] In one embodiment of the brake pad, the density of the reinforcement elements in the underlayer can be at least 10% or at least 15% and / or at most 40%. That is, the reinforcement elements can constitute at least 10% or at least 15% and / or at most 40% of the volume and / or mass of the underlayer. In an optional example, the reinforcement elements are fibers or rods made of mineral, glass, or metal.

[0034] In one example, the sublayer is designed to expand in the z-direction by at least 0.1 mm or at least 0.2 mm when heated from 20°C to 150°C. This expansion preferably counteracts a pressure of at least 5 bar. That is, the expansion occurs even when a pressure of 5 bar, or preferably an even higher pressure, is applied. The thickness of the sublayer can be, for example, at least 1.5 mm or at least 2 mm and / or at most 3 mm and / or at most 3.5 mm, where this thickness can, for example, be the thickness at room temperature.

[0035] In one example, the sublayer is configured to expand by at least 0.03 mm and / or at most 0.05 mm in the x-direction and / or in the y-direction when heated from 20°C to 150°C. In this sense, the sublayer can be anisotropic, for example, because it can be configured to expand more in the z-direction than in the x-direction or the y-direction when heated.

[0036] For example, the resistance to compression of the sublayer can be at least 0.0008 mm. 3 / bar and / or at most 0.0012 mm 3 The amount is / bar.

[0037] The sublayer, in particular the base material of the sublayer, can, for example, comprise at least one of the following materials: - Rubber, - Adhesive, - Phenol, - Metal particles, - Glass particles, - Sand particles, - organic particles, - Plastic particles.

[0038] The invention will now be explained by way of example with reference to the attached figures.

[0039] It contains: Fig. 1a shows a disc brake system, Fig. Figure 1b shows a brake disc with a brake pad in a non-braking state. Fig. Figure 1c shows a brake disc with a brake pad in a braking state. Fig. 2 shows a brake disc with a sublayer containing insert elements, Fig. 3 illustrates anisotropic material properties of the sublayer, Fig. Figure 4 shows a sublayer with elongated insert elements, and Fig. Figures 5a-5j show different distributions of insert elements within a sublayer.

[0040] Fig. Figure 1a shows a disc brake system comprising a rotating body in the form of a brake disc 6 and a brake caliper 5. The brake caliper 5 holds a piston 4 and two brake pads configured to be pressed against the brake disc 6. The brake pad on the right, connected to the piston 4, is configured to move in a positive z-direction for braking, as indicated by an arrow, and the opposite brake pad, held by a finger of the brake caliper 5, is configured to move in a negative z-direction for braking. After the brakes are released, both brake pads move away from the brake disc 6 and should return to and maintain their non-braking position as reliably as possible to avoid drag torque.Each brake pad comprises a backing plate 1, a sublayer 2, and a friction material 3, which are layered in this order along the z-direction (positive z-direction for the brake pad on the right and, mirrored, negative z-direction for the brake pad on the left). The sublayer 2 is more clearly visible in the following figures. As explained below, according to the present application, the sublayer 2 has an anisotropic material property, wherein at least one material parameter has a different value in the z-direction than in a direction orthogonal to the z-direction.

[0041] Fig. Figures 1b and c show enlarged views of part of the right brake pad and part of the brake disc 6. Fig. 1b shows a non-braking state, and Fig. 1c indicates a braking condition.

[0042] In the non-braking state of Fig. 1b has a gap g between the brake disc 6 and the brake pad with a target gap width of 0.1 mm to 0.15 mm, which should be reliably restored and maintained. The thickness d of the underlayer 2 is between 2 mm and 3 mm in the non-braking state.

[0043] When the brakes are applied ( Fig. 1c), the gap g disappears because the brake pads (i.e., the friction materials 3) are pressed against the brake disc 6. Heat generated by friction causes the thickness of the underlayer 2 to increase by Δd due to thermal expansion. The underlayer is configured to expand by at least 0.1 mm in the z-direction when heated from 20°C to 150°C, with this expansion occurring in the axial z-direction while resisting a pressure of at least 5 bar. The heating and expansion occur, for example, during a 15-second braking application. For example: Δd = 0.12 mm. The underlayer 2 can be configured to expand by 0.03 mm to 0.05 mm in both the x-direction and the y-direction when heated from 20°C to 150°C. In this sense, thermal expansion is anisotropic, since the expansion in the axial z-direction exceeds the thermal expansion in a plane orthogonal to the z-direction.

[0044] After the brake is released, the external load disappears and the heating of sublayer 2 stops. When sublayer 2 returns to a lower temperature, e.g., room temperature, its dimensions resume their original length, width, and height in the x, y, and z directions.

[0045] Fig. Figure 2 shows a portion of the brake disc 6 and two brake pads, each brake pad comprising a backing plate 1, a sublayer 2, and a friction material 3. The sublayer 2 comprises a base material 2.1 and insert elements 2.2 arranged within the base material 2.1. As will be explained later, the insert elements 2.2 enable the anisotropic material properties of the sublayer 2 to be provided.

[0046] In particular, the base layer 2 can be reinforced by insert elements, e.g., in the form of pieces of hard metal and / or glass, which exhibit very high compressive strength and a high coefficient of thermal expansion. The insert elements 2.2 can, for example, comprise rubber and / or minerals such as stone, and / or glass and / or metal such as steel, and / or phenol.

[0047] The base material 2.1 of sublayer 2 can include at least one of the following materials: rubber, adhesive, phenol, metal particles, glass particles, sand particles, organic particles, plastic particles.

[0048] The insert elements 2.2 have a compression modulus that is, for example, 4 to 5 times the compression modulus of the base material 2.1.

[0049] The insert elements 2.2 have a coefficient of thermal expansion that is, for example, at least three times the coefficient of thermal expansion of the base material 2.1.

[0050] For example, the material of the insert elements has a thermal expansion of 1.0 E-1 / K to 1.4 E-5 1 / K when heated, and the base material has a thermal expansion of 0.2 E-5 1 / K to 0.4 E-5 1 / K. Conversely, the material of the insert elements has a thermal contraction of -3 E-6 1 / K to -5 E-6 1 / K when cooled, and the base material has a thermal contraction of -1.2 E-6 to -1.6 E-6 1 / K.

[0051] Fig. Figure 3 shows sublayer 2 according to the application, where the axial z-axis and the x- and y-directions perpendicular to the z-direction are indicated. As already mentioned, sublayer 2 has overall anisotropic material properties. These anisotropic material properties can be provided by - an anisotropic modulus of elasticity and / or - an anisotropic shear modulus and / or - an anisotropic Poisson number, and / or - anisotropic thermal conductivity, and / or - anisotropic thermal expansion, and / or - anisotropic compressibility, and / or - an anisotropic memory module and / or - an anisotropic loss modulus.

[0052] An anisotropic elastic modulus E can, for example, have the following tensor components (in MPa): E xx = 14500 (from 12000 to 18000) E yy = 14500 (from 12000 to 18000) E zz = 4600 (from 2500 to 7500)

[0053] An anisotropic shear modulus G can have, for example, the following tensor components (in MPa): G xz = 3800 (from 1800 to 6800) G yz = 3800 (from 1800 to 6800) G xy = 6200 (from 4000 to 9500)

[0054] An anisotropic Poisson number v can, for example, have the following tensor components (dimensionless): v xz = v yz = 0.15 (from 0.12 to 0.18) vzx = v zy = 0.08 (from 0.05 to 0.10) v xy = V yx = 0.25 (from 0.18 to 0.30)

[0055] The density of the lower layer 2 is, for example, 2.3 g / cm³. 3 (2.0 to 2.5). The compressibility resistance of sublayer 2 is at least 0.0008 mm. 3 / bar and / or at most 0.0012 mm 3 / bear.

[0056] Fig. Figure 4 shows a section through a sublayer 2 with directionally oriented insert elements 2.2 arranged in the base material 2.1, according to an embodiment of the application. The insert elements 2.2 are elongated elements 2.2a. Specifically, the insert elements 2.2 shown are fibers or rods, for example made of metal and / or glass. They have an approximately circular cross-section. They are oriented longitudinally along the z-direction as the principal direction, i.e., they extend in the z-direction.

[0057] The elongated elements 2.2a have a diameter between 50 µm and 100 µm and a length between 0.5 mm and 2 mm, whereby the length of the elongated elements 2.2a, which are oriented in the z-direction, typically does not exceed the thickness of the sublayer 2.

[0058] As from Fig. As can be seen in Figure 4, the density of the elongated insert elements 2.2 in a marginal region near the outer edges of the sublayer 2 is increased compared to the density of the elongated insert elements in a central region of the sublayer 2. The marginal region is an area extending, for example, up to 2 mm from an outer edge of the sublayer 2. The central region is the part of the sublayer 2 that is surrounded by the marginal region. The insert elements 2.2 thus form a frame around the central region of the sublayer 2. In the marginal region, the average distance between adjacent insert elements 2.2, which are designed as elongated elements 2.2a, is less than their thickness, i.e., less than 0.1 mm. Some of the adjacent insert elements touch in the marginal region, resulting in a comparatively high regional volume density of the insert elements 2.2 (volume of insert elements 2.2 per volume of sublayer 2).In comparison, the volume density of the insert elements 2.2 is lower in the central area because the insert elements 2.2 are arranged in a more distributed manner.

[0059] The average total volume density of the insert elements in the sublayer 2 is between 10% and 40%.

[0060] The in Fig. The arrangement of the insert elements shown in section 4 facilitates the provision of anisotropic material properties. Further embodiments for providing anisotropic material properties are described in the following. Fig. 5b-j shown.

[0061] Fig. Figure 5a shows another overview of a brake system, with a sectional view showing the brake disc 6 and two brake pads, each brake pad having a backing plate 1, a base layer 2 and a friction material. In the following Fig. Figures 5b to 5j show embodiments of the brake pad according to this application, exemplified by the right brake pad, which is designed to be moved in the positive z-direction for braking. All information given also applies analogously to the left brake pad.

[0062] Fig. Figure 5b shows an embodiment of the brake pad in which the underlayer 2 has a base material 2.1 and insert elements 2.2, wherein the insert elements 2.2 are arranged exclusively in an edge region of the underlayer 2, at a distance of at most 3 mm or at most 2 mm from outer edges of the underlayer 2.

[0063] Fig. Figure 5c shows an embodiment of the brake pad in which the insert elements 2.2 comprise elongated elements 2.2a arranged in an edge region of the base layer 2 and extending in the z-direction. The insert elements 2.2 also comprise further insert elements 2.2b extending in the vicinity of the back plate 1, for example, orthogonal to the z-direction. The further insert elements 2.2b can be made of the same or a different material than the elongated elements 2.2a extending in the z-direction. The elongated elements 2.2a extending in the z-direction are limited to a distance of at most 3 mm or at most 2 mm from an outer edge of the base layer 2. The further insert elements 2.2b are limited to a distance of at most 0.5 mm from the back plate. The further insert elements 2.2b extend up to 1 cm towards the center of the sublayer 2, away from the outer edge of the sublayer 2.

[0064] All insert elements 2.2 can have a diameter of, for example, 50 µm to 100 µm.

[0065] Fig. Figure 5d shows an embodiment of the brake pad, in which, similar to the embodiment of Fig. 5c elongated elements 2.2a extending in the z-direction are provided, which are limited to the edge region up to 3 mm or up to 2 mm from the outer edge of the sublayer. Additionally, further insert elements 2.2b are provided at a distance of no more than 0.5 mm from the back plate 1, wherein the further insert elements 2.2b extend through the sublayer, for example over the entire sublayer. The further insert elements 2.2b can be made of the same or a different material than the elongated elements 2.2a extending in the z-direction.

[0066] Fig. Figure 5e shows an embodiment of the brake pad in which a plurality of elongated elements 2.2a are provided, extending in the z-direction. The elongated elements 2.2a are distributed over the entire volume of the sublayer 2 and are therefore not limited to an edge region of the sublayer 2. Further insert elements 2.2b, extending orthogonally to the z-direction, are also provided. The further insert elements 2.2b are limited to a distance of no more than 0.5 mm from the back plate 1.

[0067] Fig. Figure 5f shows an embodiment in which the elongated elements 2.2a are oriented in a principal direction that deviates slightly from the z-direction, wherein the elongated elements deviate from the z-direction by an angle of, for example, 30 degrees or less. The elongated elements 2.2a are angled outwards in the positive z-direction towards the outer edge of the sublayer 2.

[0068] Fig. Figure 5g shows an embodiment of the brake pad in which a plurality of different insert elements 2.2 with varying shapes and sizes are provided. They are confined to an edge region of the base layer 2, located up to 2 or 3 mm from the outer edge of the base layer 2. The insert elements 2.2 include particle-like insert elements 2.2c, which may contain rubber and / or rubber powder and / or phenol particles. The particle-like insert elements 2.2c may have an approximately spherical shape or any other shape with a diameter of, for example, at most 100 µm or at most 50 µm. The base layer 2 also contains elongated elements 2.2a with a diameter of at most 50 µm and a length of at most 0.1 mm. At least some of the elongated elements 2.2a in the edge region of the base layer are oriented along the z-direction. Additional insert elements 2 are located near the back plate 1.2b, which are aligned in one direction orthogonal to the z-direction. The further insert elements 2.2b also have a diameter of at most 50 µm and a length of at most 0.1 mm, and the further insert elements 2.2b are also restricted to the edge region.

[0069] Fig. Figure 5h shows a brake pad in which the sublayer 2 has elongated elements 2.2a with a diameter of at most 50 µm and a length of at most 0.1 mm. These elements are confined to a peripheral region of the sublayer 2, extending up to 2 or 3 mm from the outer edge of the sublayer 2. The elongated elements 2.2a are oriented along the z-direction. Additionally, further insert elements 2.2b are located near the backplate 1 and are oriented in a direction orthogonal to the z-direction. These further insert elements 2.2b also have a diameter of at most 50 µm and a length of at most 0.1 mm. The further insert elements 2.2b are distributed throughout the sublayer 2 in the immediate vicinity of the backplate 1.

[0070] Fig. Figure 5i shows a brake pad in which the sublayer 2 comprises elongated elements 2.2a with a diameter of at most 50 µm and a length of at most 0.1 mm. The elongated elements 2.2a are oriented along the z-direction and distributed throughout the entire sublayer. Additionally, further insert elements 2.2b are located near the backplate 1 and are oriented orthogonally to the z-direction. These further insert elements 2.2b also have a diameter of at most 50 µm and a length of at most 0.1 mm. These further insert elements 2.2b are distributed throughout the sublayer 2 near the backplate 1. Additionally, there are particle-like insert elements 2.2c with an approximately spherical or arbitrary shape, with a diameter of, for example, at most 100 µm or at most 50 µm, wherein the particle-like insert elements 2.2c are arranged in the edge region of sublayer 2 and extend up to 2 or 3 mm from the outer edge of sublayer 2.

[0071] Fig. Figure 5j shows a brake pad in which the sublayer 2 has elongated elements 2.2a with a diameter of at most 50 µm and a length of at most 0.1 mm. These elements are confined to a peripheral region of the sublayer 2, extending up to 2 or 3 mm from the outer edge of the sublayer 2. The elongated elements 2.2a are oriented in a direction slightly deviating from the z-direction by 30 degrees or less. The elongated elements 2.2a are angled outwards in the positive z-direction towards the outer edge of the sublayer 2. The sublayer 2 also contains dust 2.2d, which is distributed throughout the sublayer 2 but confined to the immediate vicinity of the backplate 1, up to 0.5 mm from the backplate 1. Reference symbol list 1 Backplate 2 lower class 2.1 Basic material 2.2 Insert elements 2.2a elongated elements 2.2b further insert elements 2.2c Particle-like insert elements 2.2d Dust 3 Friction material 4 pistons 5 cases 6 brake disc

Claims

[1] A brake pad for a vehicle brake, comprising a backing plate (1), a backing layer (2) and a friction material (3) layered in this order in a z-direction, the brake pad being adapted to be moved in the z-direction to be pressed against a rotating body for braking, wherein the underlayer (2) has an anisotropic material property, wherein at least one material parameter in the z-direction has a value which differs from its value in a direction orthogonal to the z-direction, wherein the underlayer comprises a base material (2.1) and insert elements (2.2) arranged in the base material (2.1), wherein at least some of the insert elements (2.2) are elongated elements (2.2a) oriented in a main direction deviating from the z-direction by a maximum of 30°, wherein in an edge region near outer edges of the lower layer (2) a higher density of insert elements (2.2) is provided than in a central region of the lower layer (2), wherein the insert elements (2.2) in the edge region frame the central region of the lower layer (2). [2] Brake pad according to claim 1, wherein the anisotropic material property is provided by - an anisotropic elastic modulus and / or - an anisotropic shear modulus and / or - an anisotropic Poisson ratio, and / or - an anisotropic thermal conductivity, and / or - an anisotropic thermal expansion, and / or - an anisotropic compressibility, and / or - an anisotropic storage modulus and / or - an anisotropic loss modulus. [3] Brake pad according to claim 1 or 2, wherein the insert elements (2.2) comprise rubber and / or minerals, such as stone, and / or glass and / or metal, such as steel, and / or phenol. [4] Brake pad according to one of the preceding claims, wherein the elongate elements (2.2a) are fibers or rods. [5] Brake pad according to one of the preceding claims, wherein the elongate elements (2.2a) extend in the z-direction. [6] Brake pad according to one of the preceding claims, wherein at least some of the insert elements (2.2), for example the elongated elements (2.2a), have a diameter of at least 40 µm or at least 50 µm and / or at most 110 µm or at most 100 µm and / or a length of at least 0.4 mm or at least 0.5 mm and / or at most or at most 3 mm or at most 2 mm. [7] Brake pad according to one of the preceding claims, wherein at least some of the insert elements (2.2) have a diameter of at most 50 µm and / or a length of at most 0.1 mm and are, for example, not aligned in a main direction. [8] Brake pad according to one of the preceding claims, wherein the edge region is limited to a distance of at most 4 mm or at most 3 mm or at most 2 mm from an outer edge of the underlayer (2) and / or the near region of the back plate is limited to a distance of at most 0.5 mm from the back plate. [9] Brake pad according to one of the preceding claims, wherein a distance between adjacent insert elements (2.2), in particular elongate elements (2.2a), in the edge region is on average less than 0.5 mm or less than 0.3 mm or less than 0.1 mm, wherein, for example, at least some of the adjacent insert elements (2.2), in particular elongate elements (2.2a), touch each other in the edge region. [10] Brake pad according to one of the preceding claims, wherein the thermal expansion coefficient of the insert elements (2.2) is at least twice the thermal expansion coefficient of the base material (2.1), preferably at least three times the thermal expansion coefficient of the base material (2.1). [11] Brake pad according to one of the preceding claims, wherein a material of the insert elements has a thermal expansion of 1.0 E-1 / K to 1.4 E-5 1 / K when heated and / or the base material has a thermal expansion of 0.2 E-5 1 / K to 0.4 E-5 1 / K and / or the material of the insert elements has a thermal contraction of -3 E-6 1 / K to -5 E-6 1 / K when cooled and / or the base material has a thermal contraction of -1.2 E-6 to -1.6 E-6 1 / K. [12] Brake pad according to one of the preceding claims, wherein the density of the insert elements (2.2), for example in the form of mineral fibers, in the underlayer is at least 10% or at least 15% and / or at most 40%. [13] Brake pad according to one of the preceding claims, wherein the underlayer is arranged such that it expands in the z-direction by at least 0.1 mm or at least 0.2 mm when heated from 20°C to 150°C, wherein the expansion preferably counteracts a pressure of at least 5 bar, wherein a thickness of the underlayer is preferably at least 1.5 mm or at least 2 mm and / or at most 3 mm and / or at most 3.5 mm. [14] Brake pad according to one of the preceding claims, wherein the underlayer (2) is arranged such that it expands by at least 0.03 mm and / or at most 0.05 mm in the x-direction and / or in the y-direction when heated from 20°C to 150°C. [15] Brake pad according to one of the preceding claims, wherein a resistance to compression of the underlayer is at least 0.0008 mm 3 / bar and / or maximum 0.0012 mm 3 / bar. [16] Brake pad according to one of the preceding claims, wherein the base material (2.1) of the underlayer (2) comprises at least one of the following components: - rubber, - Adhesive, - Phenol, - metal particles, - glass particles, - sand particles, - organic particles, - Plastic particles.

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