Brake pad for a vehicle brake and braking system

Abstract

Brake pad (7) for a vehicle brake, wherein the brake pad (7) comprises a friction lining (3) having a leading edge (3.1) and a trailing edge (3.2) at two opposite ends, a back plate (1) holding the friction lining (3), and a backing layer (2) arranged between the back plate (1) and the friction lining (3), wherein the backing layer (2) connects the friction lining (3) to the back plate (1), where (a) a front portion (2.1) of the backing layer (2) extending from a front side of the backing layer (2) located below the leading edge (3.1) of the friction lining (3), and / or (b) a rear portion (2.2) of the backing layer (2), which extends from a rear side of the backing layer (2) lying below the rear edge (3.2) of the friction lining (3), is made of a different material than a remaining part (2.3) of the backing layer, wherein the material of the front section (2.1) and / or the rear section (2.2) of the base layer (2) comprises rubber balls, wherein the rubber balls of the front section (2.1) and / or the rear section (2.2) have a diameter of at least 0.5 mm.

Description

[0001] The application relates to a brake pad for a vehicle brake and a corresponding braking system.

[0002] In a braking system, such as a disc brake system, brake pads are provided and adapted to be pressed against a rotating element, such as a brake disc. When the brake pads are pressed against the rotating element, friction is generated, which in turn slows the rotating motion. Heat, vibration, and noise are also generated. Friction is the source of noise or squeal, as the rotating element and / or the brake pads may exhibit audible high-frequency oscillations. The relative motion between the brake disc and the brake pad can lead to nonlinear friction behavior and self-excitation. Furthermore, the oscillations of the different parts of the brake, particularly the contact pairs, such as the brake disc and the brake pads, are subject to resonant behavior and / or mode locking, which can lead to increased noise and additional squeal modes.

[0003] From the document US 2017 / 0152904 A1, brake pads are known which comprise a backing layer, a backing layer which is bonded to a front surface of the backing layer and which transmits heat and vibrations generated during braking, an adhesive layer which mediates between the backing layer and the backing layer, and a friction material layer which is provided on a front surface of the backing layer and which generates friction when pressed against a disc of a brake.

[0004] JP H11-148525 A discloses a friction material for a disc brake pad of a vehicle disc brake, wherein a heat-conducting layer is formed over the entire surface of the friction material of the disc brake pad in contact with the backing metal of the disc brake pad. This is intended to achieve faster transfer of generated heat, suppression of deformation of the friction material, suppression of local wear, and elimination of braking noise through continuous and stable friction between the rotor and the friction material. A heat-conducting layer, which has better thermal conductivity than a base material of the friction material, is provided on the entire surface of the disc brake pad where the friction material contacts the backing metal.

[0005] The document DE 10 2009 022 112 A1 shows a brake pad consisting of an at least partial ceramic matrix of at least one pyrolyzed preceramic polymer with fillers embedded therein, wherein the brake pad has at least two distinct layers, of which the first layer is a friction layer that interacts tribologically with a brake disc and the second layer is a vibration-damping damping layer, each of which contains function-specific fillers.

[0006] DE 695 10 409 T2 relates to a disc brake friction pad assembly for generating effective frictional forces with reduced noise during braking operation of the system. The brake disc friction pad assembly consists of a friction pad element, a metallic base plate element, and a specially arranged, noise-damping shim subassembly consisting of a plate of elastomeric material arranged between and bonded to two spaced metallic plates.

[0007] US 2006 / 0 260 881 A1 discloses a brake pad with an integrated wear indicator feature. This comprises a brake backing plate, a backing on a surface of the brake backing plate, and at least one friction material layer on the backing, wherein the backing contains an effective amount of metal particles having a cross-sectional area of at least 0.05 mm 2and have a length of more than 0.10 mm. The pad generates a volume of at least 70 dB and a frequency of at least 1.5 kHz, measured 1.5 m from the pad, when the pad contacts a braking surface of a brake assembly, thereby clearly alerting the driver that brake maintenance is required.

[0008] JP 2000-161406 A proposes a friction material consisting of two layers: a base layer and a friction surface layer. The friction surface layer is attached to a support plate via the base layer. The base layer has an elastic property and is capable of elastically deforming according to the surface shape of a mating material when frictional sliding occurs between it and the mating material. Due to the elastic deformation of the base layer, the friction surface layer slides frictionally while following the surface shape of the mating material, and thereby the contact area with the mating material is enlarged, leading to an increase in the friction coefficient. To impart an elastic property to the base layer, the base layer is made of, for example, a rubber or resin plate or the like with a highly elastic material.

[0009] According to JP S60-249744 A, a layer of rubber powder with a diameter of less than 1,000 μm and an adhesive layer with a length of more than 0.05 mm is provided between the rear metal of a disc brake pad and a friction element. This creates a highly elastic rubber powder layer between the rear metal and the friction element, allowing the adhesive to contact the friction element through the rubber powder, thus maintaining sufficient adhesion to the rubber track. By controlling the amount of rubber powder, the compression of the disc and the amount of brake fluid can be regulated.

[0010] To reduce noise during braking, document US 5535859 A proposes a friction element for a brake pad of a disc brake, characterized by double bevels on a leading edge and a trailing edge extending from a contact surface of the friction element. Each of said double bevels has a first surface and a second surface that intersect and define a point that forms initial contact with a brake disc and dampens audible noise generated during brake application.

[0011] Chamfers have the disadvantage of reducing the effective friction surface designed to contact the brake disc during braking, thereby reducing braking performance and service life. Conversely, the brake pad must be larger to achieve a given effective friction surface, making it heavier.

[0012] It is an object of the present invention to solve or reduce the problems of noise, vibration and harshness in a braking system while avoiding any additional weight of the braking system.

[0013] This is achieved by a brake pad according to independent claim 1. Advantageous embodiments are described in the dependent claims as well as the description and the figures.

[0014] The brake pad comprises a friction lining with a leading edge and a trailing edge, the leading and trailing edges being located at two opposite ends of the friction lining. The friction lining is held in place by a backing plate. A backing layer is arranged between the backing plate and the friction lining, connecting the friction lining to the backing plate.

[0015] In the brake pad presented here, a front portion of the backing layer, which extends from a front side of the backing layer located below the leading edge of the friction lining, is made of a different material than a remaining portion of the backing layer. Additionally or alternatively, a rear portion of the backing layer, which extends from a rear side of the backing layer located below the rear edge of the friction lining, is made of a different material than a remaining portion of the backing layer.

[0016] This means that at least one of the front portion and the rear portion is made of a different material than the remaining portion. If both the front portion and the rear portion are made of a different material than the remaining portion, the material of the front portion may be the same as the material of the rear portion, or the material of the front portion may be different from the material of the rear portion.

[0017] The material of the front portion and / or the rear portion of the backing layer comprises rubber balls, wherein the rubber balls of the front portion and / or the rear portion have a diameter of at least 0.5 mm.

[0018] Using a brake pad with the properties defined above, braking noise, vibration and hardness can be effectively reduced.

[0019] As indicated, the pressure typically increases abruptly during braking when the brake pad first engages the brake disc, resulting in audible vibrations in a frequency range between 1 kHz and 16 kHz. It has been found that a large contribution to these vibration modes is made by out-of-plane modes of the disc, combined with bending modes of the pads. An underlay layer of the type discussed here can lead to mode decoupling, particularly of these modes, and thus to fewer squeal modes. Furthermore, resonant behavior can generally be avoided. In particular, an underlay layer of the type described here suppresses excitation of the corresponding oscillations by providing the different material at the leading edge and / or the trailing edge, i.e., in areas particularly susceptible to vibration excitation.Vibration suppression has been found to be effective over a wide frequency range, which is different from chamfers, which have been found to be effective only in a narrow frequency range.

[0020] Compared to chamfers, an underlay layer as described here is easier to manufacture and requires no additional steps. In addition, in contrast to designs that incorporate chamfers, modifying the material properties in the front and / or rear sections of the underlay layer neither results in a reduced effective friction surface, nor does the surface area of the friction surface change over time as the brake wears. Compared to state-of-the-art brake pads, the brake pads presented here represent a more effective and robust solution for reducing braking noise. It is also worth mentioning that both the braking effect and the vibration behavior are less subject to change over the lifetime of the brake pad than in the case of brake pads according to the aforementioned state-of-the-art.The effective friction surface designed to contact the brake disc can remain constant throughout the lifetime of the brake pad, even as the brake pad wears. Furthermore, the effective friction surface area can be the same size as the backing plate area (and thus, in typical configurations, the same size as the backing layer area). Consequently, the brake pad presented here achieves an ideal ratio between the friction surface area and the overall size and weight of the brake pad. In particular, such a brake pad is lighter than a chamfered brake pad with the same (initial) effective friction surface area.

[0021] In one embodiment of the brake pad proposed here, the material of the front portion and / or the material of the rear portion may differ from the material of the remaining part in that it has greater damping and / or a different modulus of elasticity.

[0022] In designs where the modulus of elasticity differs, the material of the front portion and / or the rear portion typically has a lower modulus of elasticity than the material of the remaining portion.

[0023] This special type of material modification is very effective in reducing brake noise as vibrations in the front section and / or rear section are dampened.

[0024] In one possible embodiment, in the front section and / or in the rear section both the damping is higher than in the remaining part and the modulus of elasticity is lower than in the remaining part.

[0025] The elastic modulus, which is varied in the sections of the backing layer as described above, can be one or more of Young's modulus (E-modulus), shear modulus (G-modulus), bulk modulus (K-modulus) and Poisson's ratio.

[0026] According to possible embodiments of the brake pad presented here, at least the material of the front section and / or the material of the rear section is softer than the friction lining. In typical designs of this type, the material of the remaining part is also softer than the friction lining.

[0027] In the brake pad described herein, at least one of the material of the front portion and the material of the rear portion may differ in density from the material of the remaining portion. Typically, in these cases, the material of the front portion and / or the rear portion has a lower density than the material of the remaining portion.

[0028] It is possible that the material of the front section and the material of the rear section differ in damping and / or elastic modulus and / or density.

[0029] For example, the friction lining can have a thickness of at least 8 mm and / or at most 15 mm.

[0030] For example, the back plate of the brake pad can be made of metal to provide good support for the friction lining.

[0031] The thickness of the backing layer can, for example, be at least 1 mm and / or at most 5 mm, in particular between 2 mm and 3 mm. This allows the desired physical effects to be achieved without adding too much additional material to the brake pad.

[0032] For example, the front portion of the backing layer may have a length of at least 8 mm and / or at most 15 mm, measured between the remaining part of the backing layer and the front side of the backing layer. Alternatively or additionally, the rear portion of the backing layer may have a length of at least 8 mm and / or at most 15 mm, measured between the remaining part of the backing layer and the rear side of the backing layer.

[0033] In relative terms, the length of the front section and / or the length of the rear section may, for example, each be between 5% and 25% of a total length of the backing layer - measured in the same direction.

[0034] The front portion, the remaining portion, and the rear portion may each have an identical width, the width being measured in a direction orthogonal to the length discussed above, and orthogonal to the thickness of the backing layer.

[0035] For the physical dimensions described above, particularly efficient suppression of braking noise was observed.

[0036] The friction lining material may, for example, contain at least one of copper, iron sulfide, graphite, zinc powder, basalt, calcium carbonate, tin sulfide, zinc aluminum, phenolic resin, rubber dust, and mineral fiber. These materials exhibit good braking performance and heat transfer when engaged with the brake disc.

[0037] The backing layer may, for example, contain rubber dust and / or adhesive and / or rubber beads. This typically means that each of the materials of the front portion, the rear portion, and the remaining part of the backing layer contains rubber dust and / or adhesive and / or metal. The adhesive used here may, for example, be a resin.

[0038] The above-mentioned materials for the base layer show good damping behavior and a modulus of elasticity that can be advantageous for the functionality of the brake pad presented here.

[0039] The materials of the front portion and / or the rear portion of the backing layer comprise rubber spheres. Rubber spheres may be provided in the remaining portion, in addition to the presence of rubber spheres in the front portion and / or the rear portion. In embodiments of the latter type, it is possible for the material of the front portion and / or the material of the rear portion to have a higher volume density of rubber spheres than the material of the remaining portion.

[0040] Alternatively or additionally, in designs with rubber balls, the number of rubber balls per volume in the material of the front section and / or in the material of the rear section may be higher than in the material of the remaining part. In designs of the proposed brake pad, the rubber balls contained in the material of the front section and / or in the material of the rear section may also be larger than those provided in the material of the remaining part.

[0041] The rubber balls of the front section and / or the rear section have a diameter of at least 0.5 mm. For example, they have a diameter of at most 1 mm. If rubber balls are also contained in the material of the remaining part, the rubber balls contained therein can, for example, have a diameter of at least 0.2 mm and / or at most 0.4 mm.

[0042] Rubber spheres provided in any of the ways described above represent a way to adjust the damping and / or elastic modulus and / or density of the respective sections of the backing layer in which they are provided. In particular, a particular desired ratio of elastic modulus and / or damping for good noise reduction can, for example, be advantageously achieved with any of the rubber sphere configurations described above.

[0043] For example, it may be provided that a resin contained in the material of the front portion and / or the material of the rear portion is softer than a resin contained in the material of the remaining part.

[0044] It is not excluded that a brake pad with the properties described above may have additional chamfers and / or be used with additional washers.

[0045] The invention also relates to a braking system comprising a brake disc, at least one brake cylinder, at least one piston, and at least one brake pad of the type described above. The braking system is configured to press the brake pad against a surface of the brake disc by activating the piston. Typically, the braking system comprises a first brake pad and a second brake pad, at least one of which is configured as a brake pad according to any one of the embodiments described herein. In possible embodiments of the braking system, both the first and second brake pads are brake pads of the type described herein. First and second brake pads are typically pressed against opposite surfaces of the brake disc during braking when the piston is activated.If two brake pads with the properties described above are provided, both can have the same properties and, for example, be arranged in a mirrored manner with respect to the brake disc. However, it is also possible for the properties of the two brake pads to differ from each other.

[0046] The invention will now be explained by way of example with reference to figures.

[0047] It shows Fig. 1 is a horizontal sectional view of a braking system with a brake pad according to the invention and Fig. 2 a vertical sectional view of the Fig. 1 shown braking system.

[0048] In Fig. Figure 1 shows a schematic representation of components of a braking system with two brake pads 7, wherein both brake pads 7 correspond to a possible embodiment envisaged by the present patent. The figure shows a horizontal sectional view of said components of the braking system, i.e., a view from above, revealing a layered structure of the brake pads 7. It should be noted that, for clarity, the figure is not to scale. It should also be noted that, although this is referred to as a "horizontal" sectional view, the brake pads can also be arranged in a different orientation.

[0049] The two brake pads 7 are arranged on opposite sides of a brake disc 6 and are held by a brake caliper 5.

[0050] Each of the two brake pads 7 comprises a backing plate 1, a backing layer 2 and a friction lining 3.

[0051] The backplate 1 is made of metal. Arranged on the backplate is the underlay layer, which has a thickness of between 2 mm and 3 mm. This is followed by the friction lining, which is between 8 mm and 15 mm thick.

[0052] The friction lining material contains copper, iron sulfide, graphite, zinc powder, basalt, calcium carbonate, tin sulfide, zinc aluminum, phenolic resin, rubber dust, and mineral fiber. The backing layer contains rubber dust, a resin that acts as an adhesive, and metal. In this way, the backing plate 1, the backing layer 2, and the friction lining 3 can be joined together by pressing.

[0053] Furthermore, a piston 4 is provided for each of the brake pads 7, by which each of the brake pads 7 is movably mounted on the brake caliper 5 so that it can be pressed against a surface of the brake disc 6. For this purpose, each of the pistons 4 is movably arranged in one of two wheel brake cylinders formed by and constituting a part of the brake caliper 5.

[0054] The structure of the two brake blocks 7 is identical. However, in the embodiment shown in the figure, they are mirror-inverted with respect to the brake disc 6 in order to achieve the same functionality for both brake blocks 7, since they are arranged on opposite sides of the brake disc 6. In other embodiments, however, it is also possible for the two brake blocks 7 to have different structures and / or for them not to be mirror-inverted. It is even possible for only one of the two brake blocks to be a brake block according to this patent.

[0055] In the braking system shown, the brake pads 7 are held by a brake caliper 5 and are adapted to be moved in a direction toward the brake disc 6. The friction lining 3 can thereby be pressed against the brake disc 6 for braking. Typically, an elastic seal (not shown) is provided around the piston 4 so that hydraulic pressure can be exerted on the piston 4, the seal allowing movement of the piston 4 and the brake pad 7 toward the brake disc 6. Due to its elastic properties, the seal can cause a retracting movement of the piston 4 and the brake pad 7 once the pressure is no longer applied.

[0056] The brake disc 6 can rotate in a preferred direction of rotation, which corresponds, for example, to a forward movement of the vehicle. The preferred direction of rotation, represented by an arrow in the Fig. 1, allows a definition of a leading edge 3.1 and a trailing edge 3.2 of the friction lining 3, wherein a surface area of the brake disc 6 that interacts with the friction lining 3 moves from the leading edge 3.1 to the trailing edge 3.2 with respect to the brake pad 7. A length of the friction lining—and thus, in the present example, a length of the brake pad—is given by the distance between the leading edge 3.1 and the trailing edge 3.2.

[0057] The backing layer 2 comprises a front section 2.1, a rear section 2.2, and a remaining part 2.3, wherein the front section 2.1 extends between the remaining part 2.3 of the backing layer 2 and a front side of the backing layer 2, which lies below the leading edge 3.1 of the friction lining 3, and the rear section 2.2 extends between the remaining part 2.3 of the backing layer 2.3 and a rear side of the backing layer 2, which lies below the rear edge 3.2 of the friction lining 3. The remaining part 2.3 thus forms a central section of the backing layer 2.

[0058] A material of the front section 2.1 and a material of the rear section 2.2 each differ from a material of the remaining part 2.3 in that they have greater damping and / or a lower modulus of elasticity.

[0059] The brake pad 7 with the properties shown in the figure ensures that squeal modes that may occur during braking due to vibrations generated when the brake disc 6 interacts with the friction lining are efficiently suppressed. Resonances and mode coupling can be avoided over a wide range of frequencies, particularly audible ones. The brake pad 7 therefore results in reduced braking noise, reduced vibrations, and reduced harshness, thus providing comfort to an occupant of a vehicle in which the braking system is provided. The vibrations are efficiently canceled by providing different material properties in the front section 2.1 and in the rear section 2.1 of the backing layer, taking into account the particular vulnerability of these areas, as they are located below the leading edge 3.1 and the trailing edge 3.2, where vibrations typically originate.

[0060] The material of the front section 2.1 and the material of the rear section are in the version shown in Fig. 1. However, they differ from each other in other possible embodiments under this patent.

[0061] The materials of the front section 2.1 and the rear section 2.2 also have a lower density than the material of the remaining part 2.3.

[0062] The backing layer, the friction lining and the backing plate may have an area of identical size in planes parallel to a surface of the friction lining adapted to interact with the brake disc, ie they may all have the same width and length.

[0063] The front section and the rear section may each have a length of between 8 mm and 15 mm; in particular, they are each 12 mm long, the length being measured in the horizontal direction in the figure from the respective edge of the brake pad to the remaining part 2.3.

[0064] The rubber dust, resin, and metal contained in the backing layer 2 are each contained in the materials of all three sections of the backing layer 2. Furthermore, rubber balls are provided in each of the regions of the backing layer. The rubber balls are provided such that the material of the front section 2.1 and the material of the rear section 2.2 each have a greater volume density and number density of rubber balls than the material of the remaining part 2.3. Furthermore, rubber balls contained in the material of the remaining part 2.3 have a diameter of at least 0.2 mm and / or at most 0.4 mm, whereas rubber balls contained in the material of the front section 2.1 and the rear section 2.2 have a diameter of at least 0.5 mm and / or at most 1 mm.

[0065] The resin contained in the material of the front section 2.1 and in the material of the rear section 2.2 is softer than the resin contained in the material of the remaining part 2.3.

[0066] In Fig. 2 is a sectional view which is different from the view shown in Fig. 1 is rotated by 90°, i.e., a front view is shown. The two brake pads 7 are arranged so that they can be pressed against the brake disc 6 in an upper region of the brake disc 6, and it can be seen that the brake caliper 5 holds both pistons 4. It can also be seen that the backing plate 1, the backing layer 2, and the friction lining 3 all have the same width. List of reference symbols 1 back plate 2 underlay layers 2.1 Front section 2.2 Rear section 2.3 Remaining part 3 friction lining 4 pistons 5 brake caliper 6 brake disc 7 brake pad 7.1 Leading page 7.2 Rear side

Claims

[1] Brake pad (7) for a vehicle brake, wherein the brake pad (7) comprises a friction lining (3) having a leading edge (3.1) and a trailing edge (3.2) at two opposite ends, a back plate (1) holding the friction lining (3), and a backing layer (2) arranged between the back plate (1) and the friction lining (3), wherein the backing layer (2) connects the friction lining (3) to the back plate (1), where (a) a front portion (2.1) of the backing layer (2) extending from a front side of the backing layer (2) located below the leading edge (3.1) of the friction lining (3), and / or (b) a rear portion (2.2) of the backing layer (2), which extends from a rear side of the backing layer (2) lying below the rear edge (3.2) of the friction lining (3), is made of a different material than a remaining part (2.3) of the backing layer, wherein the material of the front section (2.1) and / or the rear section (2.2) of the base layer (2) comprises rubber balls, wherein the rubber balls of the front section (2.1) and / or the rear section (2.2) have a diameter of at least 0.5 mm. [2] Brake pad (7) according to claim 1, characterized by that the other material of the front section (2.1) and / or the rear section (2.2) has a stronger damping and / or a different modulus of elasticity than a material from which the remaining part (2.3) is made. [3] Brake pad (7) according to one of the preceding claims, characterized bythat the other material of the front section (2.1) and / or the rear section (2.2) has a different density than the material of the remaining part (2.3). [4] Brake pad (7) according to one of the preceding claims, characterized by in that the front section (2.1) extends between the front side (2.1) of the backing layer (2) and the remaining part (2.3) of the backing layer (2) over a length of at least 8 mm and / or at most 15 mm, and / or in that the rear section (2.2) extends between the rear side of the backing layer (2) and the remaining part (2.3) of the backing layer (2) over a length of at least 8 mm and / or at most 15 mm. [5] Brake pad (7) according to one of the preceding claims, characterized by that the base layer (2) has a thickness of at least 1 mm and / or at most 5 mm. [6] Brake pad (7) according to one of the preceding claims, characterized bythat the friction lining (3) is made of a material which contains at least one of copper, iron sulfide, graphite, zinc powder, basalt, calcium carbonate, tin sulfide, zinc aluminum, phenolic resin, rubber dust and mineral fiber. [7] Brake pad (7) according to one of the preceding claims, characterized by that the materials of the front section (2.1) and the rear section (2.2) and the remaining part (2.3) of the backing layer (2) each contain rubber dust and / or adhesive and / or metal. [8] Brake pad (7) according to one of the preceding claims, characterized by that the materials of the front section (2.1) and the rear section (2.2) and the central section (2.3) of the backing layer (2) each include rubber balls. [9] Brake pad (7) according to claim 8, characterized byin that the material of the front section (2.1) and / or the material of the rear section (2.2) has a higher volume density of rubber balls than the material of the remaining part (2.3) and / or in that a number of rubber balls per volume in the material of the front section (2.1) and / or in the material of the rear section (2.2) is higher than in the material of the remaining part (2.3). [10] Brake pad (7) according to claim 8 or 9, characterized by in that the rubber balls contained in the material of the remaining part (2.3) have a diameter of at least 0.2 mm and / or at most 0.4 mm, and in that the rubber balls contained in the material of the front section (2.1) and / or the material of the rear section (2.2) have a diameter of at most 1 mm. [11] Brake pad (7) according to one of the preceding claims, characterized bythat a resin contained in the material of the front portion (2.1) and / or in the material of the rear portion (2.2) is softer than a resin contained in the material of the remaining part (2.3). [12] Brake pad (7) according to one of the preceding claims, characterized by that the friction lining (3) has a thickness of at least 8 mm and / or at most 15 mm. [13] Brake pad (7) according to one of the preceding claims, characterized by that the back plate (1) is made of metal. [14] A braking system comprising a brake disc (6), at least one brake cylinder, at least one piston (4) and at least one brake pad (7) according to any one of the preceding claims, wherein the braking system is arranged to press the brake pad (7) against a surface of the brake disc (6) by activating the piston (4).

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