Piston for a brake caliper of a wheel brake of a vehicle, brake caliper and wheel brake for a vehicle

Abstract

Piston (3) for a brake caliper (100) of a wheel brake of a vehicle, wherein the piston (3) extends along a piston axis (A3) between a contact end (31) designed to come into contact with a friction lining (2) and an opposite rear end (32), wherein the piston (3) has: a first body segment (34); and a second body segment (36) which is arranged not overlapping with the first body segment (34) with respect to a piston circumferential direction (C3); wherein the first body segment (34) and the second body segment (36) have different elasticity properties and / or different thermal expansion properties at least in a contact zone (4), wherein the contact zone (4) is an axial section of the piston (3) extending from the contact end (31) along the piston axis (A3); wherein the first and second body segments (34, 36) each define at least 25% of the circumference of the piston (3) in order to achieve a uniform pressure distribution across a contact interface between the friction lining (2) and the piston (3), wherein the piston (3) has a rotation-prevention structure on its outer circumferential surface which is designed to engage with a rotation-prevention counter-structure in a caliper housing (1) of the brake caliper (100) in order to block rotation of the piston (3) about the piston axis (A3).

Description

TECHNICAL AREA

[0001] The present invention relates to a piston for a brake caliper of a wheel brake of a vehicle, a brake caliper and a wheel brake for a vehicle. BACKGROUND

[0002] A friction brake for a vehicle typically comprises a disc coupled to a wheel of the vehicle and a brake caliper coupled to an axle of the vehicle. The brake caliper has a pair of friction pads that are movable by means of a piston in contact with the disc to exert a braking force on the disc.

[0003] The friction pads are located on opposite sides of the disc and are typically coupled to different sections of a caliper housing, connected by a bridge extending radially outside the disc. When the piston exerts force on the friction pads, a bending moment is generated, causing slight deformation of the caliper housing. As a result, the piston tilts slightly relative to the friction pad in contact with the disc, which can lead to uneven pressure distribution at the contact interface between the piston and the friction pad. Besides potentially damaging the piston or caliper housing, such uneven pressure distribution can cause squealing noises during braking.

[0004] EP 2 944 840 A1 discloses a brake caliper in which a washer is positioned between a friction lining and a piston, the washer having windows and a web. The piston and the friction lining are in contact with opposite sides of the web, so that part of the piston can be received into the window when the friction lining and the piston tilt relative to each other.

[0005] Another piston for a disc brake is disclosed in WO 2019 / 118289 A1.

[0006] Furthermore, DE 10 2022 200 960 A1 describes a piston for a brake caliper comprising a piston wall and a piston base. The piston wall defines a hollow cylinder. The piston base forms a rear end of the piston. An end of the piston wall opposite the piston base forms a contact end, which is in contact with a brake pad. The piston wall comprises a metallic section surrounded on its outer surface by a plastic section. The metallic section of the piston wall is cut longitudinally, thus forming longitudinally extending recesses. These recesses contain plastic material that protrudes from the plastic section.

[0007] DE 195 34 220 A1 describes a plastic brake piston with a base section and a wall section that encloses a cavity. The wall section terminates in an end face that forms a contact end of the brake piston and is designed to rest against a back plate of a brake pad, wherein a U-shaped metallic insert is inserted into the cavity, the ends of which are angled to contact the brake pad.

[0008] German patent application DE 10 2021 103 509 A1 discloses a piston comprising a radially outer first tubular body section and an inner second tubular body section. The body sections are connected to each other and made of different materials. REVELATION OF THE INVENTION

[0009] One of the objectives of the present invention is to provide improved solutions for a piston of a wheel brake of a vehicle, in particular a solution that enables a more uniform pressure distribution at a contact interface between the piston and a friction lining.

[0010] For this purpose, the present invention provides a piston for a brake caliper according to claim 1, a brake caliper according to claim 10 and a wheel brake according to claim 12.

[0011] According to a first aspect of the invention, a piston is provided for a brake caliper of a wheel brake of a vehicle. The piston extends along a piston axis between a contact end, which is configured to come into contact with a friction lining, and an opposite rear end. The piston comprises a first body segment and a second body segment, which is arranged either non-overlapping with or separate from the first body segment with respect to a piston circumferential direction, wherein the first body segment and the second body segment have different elastic properties and / or different thermal expansion properties at least in a contact zone. The contact zone is an axial section of the piston extending from the contact end along the piston axis.For example, the contact zone can be a length segment with a length in the range of 1% to 50%, particularly between 1% and 25%, of the total piston length measured between the contact end and the rear end. The first and second body segments each define at least 25% of the piston's circumference to achieve a uniform pressure distribution across a contact interface between the friction lining and the piston.

[0012] According to a second aspect of the invention, a brake caliper for a wheel brake of a vehicle comprises a caliper housing comprising a first housing section, a second housing section arranged axially opposite the first housing section, and a bridge connecting the first and second housing sections, wherein a passage allowing a rotatable brake disc to pass through is defined between the first and second housing sections and is limited radially by the bridge. The brake caliper further comprises a first and a second friction lining, the first friction lining being coupled to the first housing section and the second friction lining being coupled to the second housing section. Furthermore, the brake caliper comprises a piston according to the first aspect of the invention.The piston is guided in the first housing section so as to be movable along the axial direction in order to move the first friction lining along the axial direction, and the contact end of the piston is designed to be in contact with the first friction lining. Furthermore, the second body segment of the piston is positioned closer to the bridge in the radial direction than the first body segment. Preferably, the piston is guided in the saddle housing such that the piston axis runs parallel to the axial direction. The radial direction is transverse to the axial direction.

[0013] According to a third aspect of the invention, a wheel brake for a vehicle comprises a brake caliper according to the second aspect of the invention and a disc rotatable about an axis of rotation parallel to the axial direction. The disc extends through the passage of the caliper housing and has opposing friction surfaces. The friction linings are movable by means of the piston in contact with the friction surfaces.

[0014] One of the ideas of the present invention is to provide a piston, which moves a friction lining in a brake caliper, with varying mechanical and / or thermal properties at an interface between the piston and the friction lining. In particular, the piston, which may have a circular or cylindrical shape, has at least two body segments, e.g., circular segments, in which the elastic properties and / or the coefficients of thermal expansion differ from one another. When the piston is installed in the brake caliper, one of these segments is positioned radially outside and the other radially inside. That is, the body segments of the piston contact the friction lining at different points with respect to the radial direction.This allows for a more even pressure distribution, even if the caliper housing deforms and the piston tilts relative to the friction lining, by adjusting the mechanical properties. Additionally or alternatively, pressure distribution can also be controlled in situations where the brake is subjected to high thermal loads by adjusting the coefficient of thermal expansion in the two body segments accordingly.

[0015] In general, the invention enables a more uniform pressure distribution at the contact interface between the piston and a friction lining. Furthermore, brake squealing noises can be reduced because the piston and the friction lining remain in close, defined contact with each other even if the caliper housing, e.g., the bridge, deforms during braking.

[0016] Further embodiments of the present invention are the subject of the dependent claims and the following description with reference to the drawings.

[0017] According to some embodiments, the first body segment can have a first modulus of elasticity, and the second body segment can have a second modulus of elasticity, the second being smaller than the first. For example, the second modulus of elasticity can be 3% to 5% smaller than the first. Because the second body segment is positioned radially outward, it is moved closer to the friction lining as the piston tilts. Due to the higher elasticity of the second body segment, it can deform slightly, and a more uniform pressure distribution is achieved in the event of deformation of the caliper housing by providing the radially outer segment of the piston with mechanically less rigid properties.

[0018] In general, the second body segment may exhibit higher elasticity or may be more elastic than the first body segment. Elasticity can be quantified, for example, by the elastic modulus, the shear modulus, the Poisson's ratio, or similar measures.

[0019] According to some embodiments, the first body segment can have a first coefficient of thermal expansion, and the second body segment can have a second coefficient of thermal expansion, the second being smaller than the first. For example, the second coefficient of thermal expansion can be 5% to 8% smaller than the first. This results in a more uniform pressure distribution, even under high thermal loads during braking, because the radially outer segment of the piston expands less than the radially inner segment.

[0020] According to some embodiments, the first and second body segments are arranged on opposite sides of a plane containing the piston axis, with each body segment defining between 25% and 50% of the piston's circumference. Therefore, in the case of a circular or cylindrical piston, each body segment can be a circular segment with a central angle in a range between 90 degrees and 180 degrees. For example, the piston can be a hollow cylinder and the contact end can be an annular surface. In this case, each body segment can be an annular segment extending over a range between 90 degrees and 180 degrees of the circumference.

[0021] According to some embodiments, the first and second body segments can be made of different materials. That is, the first and second body segments can be made of materials with different elasticity and / or thermal expansion properties. The first and second body segments can, for example, be connected to each other or to a third body segment, for example by welding, gluing, or a form-fit connection.

[0022] According to some embodiments, the first and second body segments have different wall thicknesses. For example, the piston may be a hollow cylinder and the contact end may be an annular surface. In this case, the wall thickness can correspond to the thickness of the cylinder wall. For example, the first body segment may have a smaller wall thickness to be less rigid or more elastic than the second body segment.

[0023] According to some embodiments, the first body segment and / or the second body segment may be subjected to heat treatment to achieve different elasticity properties. That is, the first and second body segments may even be made of the same material, for example, they may be formed in one piece, but the mechanical properties of each segment differ due to the application of different heat treatments during manufacturing.

[0024] According to some embodiments, a third body segment can be arranged between the first and second body segments with respect to the piston's circumferential direction, wherein the third body segment has elastic properties and / or different thermal expansion properties, at least in the contact zone, that differ from those of the first and second body segments. Therefore, a more uniform pressure distribution can be achieved not only in the radial direction but also in a tangential direction by providing a third body segment whose elastic properties and / or thermal expansion properties are adapted.

[0025] According to some embodiments, the piston can have a cylindrical piston body, with the first and second body segments forming part of the piston body. That is, the piston body can be assembled from the first and second piston segments and, if provided, the third body segment. For example, the first and second body segments and, if provided, the third body segment can extend over the entire length of the piston, i.e., between the contact end and the rear end.

[0026] According to some embodiments, the piston can have a cylindrical piston body, and the first and second body segments, and, if provided, the third body segment, can be attached to an axial end of the piston body. For example, the body segments can be ring segments or disc segments that are attached to the end of the piston body, e.g., joined to it or detachably connected to it. That is to say, the body segments form the contact end of the piston.

[0027] According to some embodiments, the brake caliper can further have a carrier that movably guides the carrier housing, with the second friction lining being attached to the first housing section. That is, the brake caliper can be a floating brake caliper.

[0028] According to the invention, the piston is guided in the saddle housing in such a way that rotation of the piston about the piston axis is blocked. In other words, the piston is a non-rotating piston. According to the present invention, the piston has an anti-rotation structure on its outer circumferential surface which engages with an anti-rotation counter-structure in the saddle housing. For example, one of the anti-rotation structure and the anti-rotation counter-structure can be a groove extending along the axial direction or the piston axis, and the other of the anti-rotation structure and the anti-rotation counter-structure can be a projection that engages with the groove.

[0029] The features and advantages described here with respect to one aspect of the invention are also disclosed for the other aspects and vice versa.

[0030] With regard to directions and axes, in particular with regard to directions and axes relating to the course of physical structures, the course of an axis, direction or structure “along” another axis, direction or structure shall be understood to mean that these, in particular the tangents resulting at a respective point of the structures, each run at an angle of less than 45 degrees, preferably less than 30 degrees and in particular preferably parallel to each other.

[0031] With regard to directions and axes, in particular with regard to directions and axes relating to the course of physical structures, the course of an axis, direction or structure “perpendicular” to another axis, direction or structure shall be understood to mean that these, in particular the tangents resulting at a respective point of the structures, each run at an angle of greater than or equal to 45 degrees, preferably greater than or equal to 60 degrees and in particular preferably perpendicular to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] For a more complete understanding of the present invention and its advantages, reference is now made to the following description in conjunction with the accompanying drawings. The invention is explained in more detail below with reference to exemplary embodiments shown in the schematic figures of the drawings. These show: Fig. 1 A schematic cross-sectional view of a vehicle brake according to an embodiment of the invention. Fig. 2 a schematic top view of a contact end of a piston according to an embodiment of the invention. Fig. 3 a schematic sectional view of the in Fig. 2 pistons shown. Fig. 4 a schematic sectional view of a piston according to a further embodiment of the invention. Fig. 5 a schematic sectional view of a piston according to a further embodiment of the invention. Fig. 6 a schematic top view of a contact end of a piston according to a further embodiment of the invention.

[0033] In the figures, identical reference symbols denote identical elements, unless otherwise specified. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0034] Fig. Figure 1 schematically shows a vehicle brake 200 for a vehicle. The brake 200 can be used, for example, in a car, a bus, a truck, a motorcycle, or similar vehicle. As shown in Fig. As shown schematically in Figure 1, the brake 200 comprises a brake caliper 100 and a brake disc 210.

[0035] As in Fig. The brake disc 210, shown schematically in Figure 1, will not be described in detail below. In general, the disc 210 can have a circular shape and comprises opposing friction surfaces 210a and 210b. The disc 210 is designed to be coupled to a wheel of the vehicle and is rotatable about the axis of rotation A200.

[0036] The brake caliper 100 is in Fig. Figure 1 is shown in a simplified and schematic manner. As shown, the brake caliper 11 comprises a caliper housing 1, a pair of friction linings 2A, 2B and a piston 3.

[0037] The saddle housing 1 has a first housing section 11, a second housing section 12 and a bridge 13.

[0038] As in Fig. As shown schematically in Figure 1, the first housing section 11 can have a guide structure, e.g., in the form of a cylindrical bore 15 for guiding the piston 3. The second housing section 12 is arranged opposite the first housing section 11 with respect to an axial direction A. As shown in Figure 1, the first housing section 11 can be guided by a guide structure, e.g., a cylindrical bore 15 for guiding the piston 3. The second housing section 12 is arranged opposite the first housing section 11 with respect to an axial direction A. Fig. As shown schematically in Figure 1, the second housing section 12 can extend along a radial direction R that is transverse to the axial direction A. For example, the second housing section 12 can have the shape of a finger, as shown in Figure 1. Fig. Figure 1 is shown schematically and by way of example. The first and second housing sections 11, 12 are connected to each other by the bridge 13, which extends essentially along the axial direction A. For example, the first housing section 11, the second housing section 12 and the bridge 13 can be formed in one piece.

[0039] As further in Fig. As shown schematically in Figure 1, the first housing section 11, the second housing section 12, and the bridge 13 define a passage 14. The passage 14 is bounded in the axial direction A by the first housing section 11 and the second housing section 12 and in the radial direction R by the bridge 13. The brake disc 210 extends through the passage 14, as shown in Figure 1. Fig. 1 shown schematically.

[0040] The saddle housing 1 can be movably mounted on a support (not shown). The support can be mounted on a steering knuckle or, more generally, on the axle of the vehicle. In particular, the saddle housing 1 can be movably guided on the support along the axial direction A. In general, the axial direction A and the axis of rotation A200 can be parallel to each other.

[0041] The friction linings 2A, 2B are positioned on opposite sides of the passage 13 and are coupled to the saddle housing 1, for example via corresponding clamps (not shown). In general, at least one of the friction linings 2A, 2B is coupled to the saddle housing 1 such that it is movable by the piston 3 along the axial direction A. In the example of Fig. 1 a first friction lining 2A is movably guided along the axial direction A in the first housing section 11, and a second friction lining 2B is fixedly attached to the second housing section 12.

[0042] In general, as in Fig. Figure 1 schematically shows that each friction lining 2A, 2B comprises a carrier plate 21, which is made of a rigid material and provides a mechanically stiff support, and a friction layer 22, which is arranged on the carrier plate 21. The friction layer 22 is made of a friction material and is designed to be pressed against the friction surface 210a, 210b of the brake disc 210 in order to generate a frictional force for braking the disc 210.

[0043] The piston 3, whose configuration is explained in more detail below, is guided movably in the first housing section 11 along the axial direction A in order to move the first friction lining 2A along the axial direction A. As in Fig. As shown by way of example in Figure 1, the piston 3 can be guided in the bore 15. The piston 3 can be moved towards and away from the passage 14 by applying hydraulic pressure to a rear end 32 of the piston. However, the invention is not limited to this. The piston 3 can also be moved using an electric actuator, such as a motor, or by means of electromagnetic force. The piston 3 is a non-rotating piston. That is, the piston 3 is guided in the bore 15 in such a way that it cannot rotate about its longitudinal axis A3. Anti-rotation structures (not shown) are formed in the first housing section 11 and on the piston 3, which engage with each other to prevent rotation of the piston 3.

[0044] A contact end 31 of the piston 3 is designed to be in contact with, or come into contact with, the first friction lining 2A, in particular with the carrier plate 21 of the first friction lining 2A. In the example of Fig. 1. The caliper housing 1 can be movably mounted on a support (not shown) along the axial direction A, as explained above. When the piston 3 moves the first friction lining 2A into contact with the friction surface 210a of the disc 210, an axial displacement of the caliper housing 1 occurs, which moves the second friction lining 2B into contact with the opposite friction surface 210b of the disc 210. Consequently, a frictional force is generated between the friction linings 2A, 2B and the disc 210, which brakes the disc 210. A movement of the piston 3 in the opposite direction generally causes the friction linings 2A, 2B to be lifted off the friction surfaces 210a, 210b. When the friction linings 2A, 2B are pressed against the friction surfaces 210a, 210b via the piston 3, a bending moment acts particularly on the bridge 13, which can cause a deformation of the saddle housing 1.In particular, the piston axis A3 can be slightly tilted relative to the axis of rotation A200 of the disc 210, or more generally, relative to the axial direction A. Since the friction lining 2A remains in contact with the friction surface 210a, tilting of the piston 3 can cause an uneven pressure distribution across the friction lining 2A with respect to the radial direction R. This effect can even be amplified due to the thermal expansion of the piston 3 under high thermal loads that can occur during braking. As a result, wear of the friction linings 2A and 2B can be uneven, braking efficiency can be reduced, and squealing noises can occur.To reduce these effects, the present invention provides the piston 3 with at least one radially inner body segment 34 and one radially outer body segment 36 with different elastic properties and / or different coefficients of thermal expansion in order to achieve a more uniform pressure distribution over the contact interface between the friction lining 2A and the piston 3.

[0045] Fig. Figure 2 shows a top view of a contact end 31 of a piston 3. Fig. Figure 3 shows a sectional view of piston 3. Fig. 2.

[0046] As exemplified in the Fig. 2 and Fig. As shown in Figure 3, the piston 3 generally extends along a piston axis A3 between a contact end 31, which is designed to come into contact with the friction lining 2A, and an opposite rear end 32. A length L3 of the piston 3 can be measured between the contact end 31 and the rear end 32.

[0047] The piston 3 has a piston body 30 that extends along and defines the piston axis A3. The piston body 30 can be a hollow cylinder, as exemplified in the Fig. 2 and Fig. 3 shown, and extends between opposite axial ends 30A, 30B. At a first axial end 30A, the piston main body 30 can be open, so that the first axial end 30A is formed by an annular end surface. At a second axial end 30B of the piston main body 30, a base 33 can be provided, as exemplified in Fig. 3 shown.

[0048] As further in the Fig. 2 and Fig. As shown in Figure 3, the piston 3 has a first body segment 34 and a second body segment 36. The first and second body segments 34 and 36 are generally separate segments of the piston 3. The body segments 34 and 36 can form part of the main piston body 30, as exemplified in Figure 3. Fig. 3 shown. However, the invention is not limited thereto and the body segments 34, 36 can also be components separate from the piston main body 30, as shown below with reference to Fig. 5 will be explained in more detail.

[0049] In general, a body segment 34, 36 is a segment that defines a portion of the circumference of the piston 3. The body segments 34, 36 therefore extend along a piston circumferential direction C3 and partially surround the piston axis A3, extending with respect to the piston axis A3 at least into a contact zone 4 of the piston 3. The contact zone 4 is an axial section of the piston 3 extending from the contact end 31 along the piston axis A3. For example, the contact zone 4 can be a length segment with a length in a range between 1% and 50%, and in particular between 1% and 25%, of the total length L3 of the piston. The body segments 34, 36 are separate, i.e., they do not overlap each other in the piston circumferential direction C3. For example, the body segments 34, 36 can be arranged on opposite sides of a plane E3 which contains the piston axis A3.

[0050] As exemplified in Fig. As shown in Figure 2, the first body segment 34 and the second body segment 36 together can form the entire circumference of the piston 3. In this example, the first body segment 34 and the second body segment 36 each extend over 50% of the circumference of the piston 3. In other words, the first and second body segments 34 and 36 can each be annular segments with a central angle of 180 degrees. In general, the first and second body segments 34 and 36 are arranged on opposite sides of the plane E3, and each body segment 34 and 36 can define between 25% and 50% of the circumference of the piston main body 30.

[0051] The first body segment 34 and the second body segment 36 exhibit different elastic properties and / or different thermal expansion properties, at least in the contact zone 4. For example, the first body segment 34 may have a first modulus of elasticity, and the second body segment 36 may have a second modulus of elasticity, and the second modulus of elasticity may be smaller than the first. For example, the second modulus of elasticity may be 3% to 5% smaller than the first modulus of elasticity. In other words, the second body segment 36 may be more elastic than the first body segment 34. Therefore, less force is required to deform the second body segment 36 to a predefined change in length.Therefore, the elasticity of the second body segment 36 helps to reduce the local pressure increase in the radially outer part of the friction lining 2A when the piston 3 is tilted relative to the friction lining 2A due to a deformation of the saddle housing 1, as in . Fig. 1 is shown schematically by arrow 3. This results in a more even pressure distribution at the interface between the friction lining 2A and the piston 3.

[0052] In addition to or as an alternative to the variation in the modulus of elasticity between body segments 34 and 36, the first body segment 34 can have a first coefficient of thermal expansion, and the second body segment 36 can have a second coefficient of thermal expansion that is smaller than the first. For example, the second coefficient of thermal expansion can be 5% to 8% smaller than the first. Therefore, the radially outer second body segment 36 expands less with increasing temperature than the radially inner first body segment 34. This creates an effect that further increases the uneven pressure distribution in a situation where the piston 3 is tilted under the influence of high temperatures, as indicated by arrow P3 in the figure. Fig. 1 displayed, at least reduced or even avoided.

[0053] To achieve different elastic properties with increased elasticity in the second body segment 36, the first and second body segments 34, 36 can be made of different materials, as in Fig. Figure 3 illustrates this schematically. In this case, the second body segment 36 can be made of a more elastic material than the first body segment 34.

[0054] Similarly, the second body segment 36 can be made of a material with a lower coefficient of thermal expansion than the material of the first body segment 34. For example, the first body segment 34 can be made of gray cast iron, and the second body segment 36 can be made of aluminum or an aluminum alloy. In general, combinations of different metal materials or combinations of a metal material and a plastic material, especially a thermoset material, are possible. The individual body segments 34, 36, if made of metal, can be manufactured by a casting, forging, or turning process. The individual body segments 34, 36, if made of plastic, can be cast, for example.

[0055] If body segments 34 and 36 are made of different materials, they can be connected to each other or to another body segment (in the Fig. 2 and Fig. (3 not shown) are coupled to form the piston main body 30. For example, body segments 34, 36 and, if provided, another body segment can be welded or bonded together or can be positively connected.

[0056] Another way to achieve different elastic properties with increased elasticity in the second body segment 36 is to have different wall thicknesses t34, t36 between the first and second body segments 34, 36. For example, the second body segment t36 can have a smaller wall thickness t36 than the first body segment t34, as shown in Fig. Figure 4 shows this schematically. Additionally or alternatively, it can also be provided that the first body segment 34 and / or the second body segment 36 have been subjected to heat treatment in order to achieve different elasticity properties in the first and second body segments 34, 36. That is, the piston main body 30 can also be manufactured from a single piece, and the sections of the piston main body 30 that form the first and second body segments 34, 36 can be subjected to different heat treatments, so that the second body segment 36 is treated to exhibit higher elasticity than the first body segment 34.

[0057] In the Fig. Figures 2 to 4 show pistons 3 in which the first and second body segments 34, 36 form part of the piston main body 30. That is, the first and second body segments 34, 36 are joined together to form the piston main body 30, or a one-piece piston main body 30 is formed with locally different wall thicknesses t34, t36 or has been subjected to locally different heat treatments. Alternatively, as exemplified in Fig. 5 shown, the first and second body segments 34, 36 are attached to the first axial end 30A of the piston main body 30, e.g. by gluing, welding, screwing or similar.

[0058] Fig. Figure 6 shows another piston 3 in a top view of its contact end 31. The piston 3 in Fig. 6 differs from the one in the Fig. 2 and Fig. 3 only by the fact that it additionally has third and fourth body segments 35, 37. The third and fourth body segments 35, 37 can be arranged between the first and second body segments 34, 36 with respect to the piston circumferential direction C3. Although Fig. 6 shows a third body segment 35 and a fourth body segment 37, it may also be provided that only a third body segment 35 is provided in addition to the first and second body segments 34, 36.

[0059] The third body segment 35 and / or the fourth body segment 37 may exhibit elastic properties and / or different thermal expansion properties that differ from those of the first and second body segments 34, 36, at least in the contact zone 4. For example, the third body segment 35 and / or the fourth body segment 37 may exhibit increased elasticity compared to the first body segment 34. Additionally or alternatively, the third body segment 35 and / or the fourth body segment 37 may have a lower coefficient of thermal expansion than the first body segment 34. The third body segment 35 and, if provided, the fourth body segment 37 may form part of the piston main body 30 or may be attached to the first axial end 30A of the piston main body 30.Furthermore, the third body segment 35 and, if provided, the fourth body segment 37 may be made of a different material than the first body segment 34 and / or the second body segment 36, or may have a different wall thickness. It may also be provided that these body segments 35, 37 have undergone different heat treatments, as explained above. As exemplified in . Fig.As shown in Figure 6, the first to fourth body segments 34, 36, 35, 37 can each form an equal part of the circumference of the piston 3. However, it is also possible for the third and fourth body segments 35, 37 to have a smaller circumference than the first and / or the second body segment 34, 36. In general, the third body segment 35 can comprise between 25% and 50% of the circumference of the piston 3, and the fourth body segment 37 can define the remainder of the circumference of the piston 3 that is not formed by the first to third body segments 34, 35, 36. REFERENCE MARK LIST 1 saddle housing 2A, 2B Friction linings 3 pistons 4 Contact zone 11 first housing section 12 second housing section 13 Bridge 14th round 15 bore 21 Carrier plate 22 Friction layer 30 piston main bodies 30A first axial end 30B second axial end 31 contact ends 32 rear end 33 Floor 34 first body segment 35 third body segment 36 second body segment 37 fourth body segment 100 brake calipers 200 wheel brake 210 brake disc 210a Friction surface 210b friction surface A axial direction A3 piston axle A200 rotary axis C3 Piston circumferential direction L3 Length of piston R radial direction t34 Wall thickness of the first body segment t36 Wall thickness of the second

Claims

[1] Piston (3) for a brake caliper (100) of a wheel brake of a vehicle, wherein the piston (3) extends along a piston axis (A3) between a contact end (31) designed to come into contact with a friction lining (2) and an opposite rear end (32), wherein the piston (3) has: a first body segment (34); and a second body segment (36) which is arranged not overlapping with the first body segment (34) with respect to a piston circumferential direction (C3); wherein the first body segment (34) and the second body segment (36) have different elasticity properties and / or different thermal expansion properties at least in a contact zone (4), wherein the contact zone (4) is an axial section of the piston (3) extending from the contact end (31) along the piston axis (A3); wherein the first and second body segments (34, 36) each define at least 25% of the circumference of the piston (3) in order to achieve a uniform pressure distribution across a contact interface between the friction lining (2) and the piston (3), wherein the piston (3) has a rotation-prevention structure on its outer circumferential surface which is designed to engage with a rotation-prevention counter-structure in a caliper housing (1) of the brake caliper (100) in order to block rotation of the piston (3) about the piston axis (A3). [2] Piston (3) according to claim 1, wherein the first body segment (34) has a first modulus of elasticity and the second body segment (36) has a second modulus of elasticity, wherein the second modulus of elasticity is smaller than the first modulus of elasticity. [3] Piston (3) according to claim 1 or 2, wherein the first body segment (34) has a first coefficient of thermal expansion and the second body segment (36) has a second coefficient of thermal expansion, wherein the second coefficient of thermal expansion is smaller than the first coefficient of thermal expansion. [4] Piston (3) according to one of the preceding claims, wherein the first and second body segments (34, 36) are arranged on opposite sides of a plane (E3) which contains the piston axis (A3), wherein each body segment (34, 36) defines between 25% and 50% of the circumference of the piston (3). [5] Piston (3) according to one of the preceding claims, wherein the first body segment (34) and the second body segment (36) are made of different materials. [6] Piston (3) according to one of the preceding claims, wherein the first body segment (34) and the second body segment (36) have different wall thicknesses (t34, t36). [7] Piston (3) according to one of the preceding claims, wherein the first body segment (34) and / or the second body segment (36) has been subjected to heat treatment to adjust different elasticity properties in the first and second body segment (34, 36). [8] Piston (3) according to one of the preceding claims, further comprising: a third body segment (35) which is arranged between the first and the second body segment (34, 36) with respect to the piston circumferential direction (C3), wherein the third body segment (35) has elasticity properties and / or different thermal expansion properties that differ from those of the first and second body segments (34, 36) at least in the contact zone (4). [9] Piston (3) according to one of the preceding claims, wherein the piston (3) has a cylindrical piston main body (30), and wherein the first and second body segments (34, 36) form part of the piston main body (30) or are attached to an axial end (30A) of the piston main body (30). [10] Brake caliper (100) for a wheel brake of a vehicle, comprising: a saddle housing (1) comprising a first housing section (11), a second housing section (12) which is arranged opposite the first housing section (11) with respect to an axial direction (A), and a bridge (13) which connects the first and the second housing section (11, 12), wherein a passage (14) which allows a rotatable brake disc (210) to pass through is defined between the first and the second housing section (11, 12) and is limited by the bridge (13) with respect to a radial direction (R); a first and a second friction lining (2A, 2B), wherein the first friction lining (2A) is coupled to the first housing section (11) and the second friction lining (2B) is coupled to the second housing section (12); and a piston (3) according to one of the preceding claims, wherein the piston (3) is guided movably in the first housing section (11) along the axial direction (A) in order to move the first friction lining (2A) along the axial direction (A); wherein the contact end (31) of the piston is designed to be in contact with the first friction lining (2A), wherein the second body segment (36) of the piston (3) is positioned closer to the bridge (13) in the radial direction (R) than the first body segment (34), and wherein the anti-rotation structure of the piston (3) engages with an anti-rotation counter-structure of the saddle housing (1) to block rotation of the piston (3) about the piston axis (A3). [11] Brake caliper (100) according to claim 10, additionally comprising a carrier which movably guides the carrier housing (1), wherein the second friction lining (2B) is attached to the first housing section (11). [12] Wheel brake (200) for a vehicle, comprising: the brake caliper (100) according to claim 10 or 11; and a disk (210) which is rotatable about an axis of rotation (A200) which is parallel to the axial direction (A), wherein the disk (210) extends through the passage (14) of the saddle housing (1) and has opposite friction surfaces (210a, 210b), and wherein the friction linings (2A, 2B) can be moved into contact with the friction surfaces (210a, 210b) by means of the piston (3).

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