Dry-running friction disc brake system for a motor vehicle

Abstract

The invention relates to a dry-running friction disc brake device (14) for a motor vehicle, comprising at least one first brake disc element (16) having at least one first friction surface (18), at least one second brake disc element (20) having at least one second friction surface (22), a pad disc element arranged between the brake disc elements (16, 20), a piston (34) designed as an annular piston which can be pressurized with hydraulic fluid and thereby hydraulically actuated, and an annular transmission element (54) arranged between the piston (34) and the first brake disc element (16), which has an axially directed projection (84) on its inner circumference, wherein the transmission element (54) and the first brake disc element (16) can be actuated by means of the piston (34) by hydraulic actuation of the piston (34).which allows the friction surfaces (18, 22) to be brought into frictional contact with the pad disc element to effect braking.

Description

[0001] The invention relates to a dry-running friction disc brake device for a motor vehicle.

[0002] DE 10 2019 118 503 A1 discloses a braking device for a wheel hub drive arrangement.

[0003] The object of the present invention is to create a particularly advantageous, dry-running friction disc brake device for a motor vehicle.

[0004] This problem is solved by a friction disc brake device with the features of claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] The invention relates to a dry-running friction disc brake system, in particular integrated into an axle component of a motor vehicle, for a motor vehicle simply referred to as a vehicle. The friction disc brake system is also simply referred to as a brake or brake system and comprises at least one first brake disc element, which has at least one first friction surface. The friction disc brake system also comprises at least one second brake disc element, which has at least one second friction surface. The brake disc elements are also simply referred to as friction elements or brake elements. The friction disc brake system also comprises a piston, which can be actuated, in particular directly, with a hydraulic fluid and thereby hydraulically actuated. This piston is also referred to as an actuating piston and is designed as an annular piston.The device includes an annular transmission element, preferably designed separately from the first brake disc element and the piston. Preferably, the first brake disc element is a brake disc. Preferably, the second brake disc element is also a brake disc. The transmission element is arranged at least partially between the piston and the first brake disc element, particularly in the axial direction of the friction disc brake assembly. The brake disc elements are rotatable relative to each other about an axis of rotation. The transmission element has an axial projection on its inner circumference, i.e., a projection directed in the axial direction of the friction disc brake assembly. The axial direction of the friction disc brake assembly, whose radial direction is perpendicular to the axial direction of the friction disc brake assembly, coincides with the axis of rotation, so that the radial direction is perpendicular to the axis of rotation.

[0006] The piston, by means of hydraulic actuation, actuates the transmission element and, via the transmission element, the first brake disc element. This allows the friction surfaces to be brought into frictional contact, particularly direct contact, with a pad element arranged axially between the brake disc elements, thus effecting braking. Braking, in this context, means that during or through braking, the pad element can be slowed down by means of frictional contact with the two brake disc elements.

[0007] Furthermore, according to the invention, the projection is operatively connected to the piston via an outer surface of the projection, wherein an axial extension of the transmission element, i.e. in the axial direction of the friction disc brake device, increases from radially outside to radially inside when viewed on a side facing away from the first brake disc element, in particular axially.

[0008] The motor vehicle, also referred to simply as a vehicle, in its fully manufactured state comprises a friction disc brake assembly, which can be referred to simply as a brake. For example, the motor vehicle in its fully manufactured state has at least one vehicle wheel, which is a ground contact element of the motor vehicle. The vehicle wheel is rotatable about a wheel axis relative to a reference element of the motor vehicle, in particular the two brake disc elements of the friction disc brake assembly. For example, the vehicle wheel can be braked, in particular slowed down, with respect to rotations about the wheel axis and relative to the reference element by means of the friction disc brake assembly, thereby, for example, braking the motor vehicle as a whole.The friction disc brake system is or constitutes a friction brake by means of which, for example, the vehicle wheel can be braked by friction. In particular, the friction disc brake system is or constitutes a service brake of the motor vehicle.

[0009] The brake pad element is rotatable with the vehicle wheel when it rotates around the wheel axis relative to the reference element, and thus rotatable around the axis of rotation relative to the brake disc elements. For this purpose, the brake pad element can be coupled to the vehicle wheel in a torque-transmitting manner, particularly in a rotationally fixed manner. By braking or decelerating the brake pad element, especially relative to the brake disc elements, the vehicle wheel can be braked, i.e., slowed down, particularly with respect to its rotations around the wheel axis relative to the reference element.

[0010] In an advantageous embodiment of the invention, it is provided that the projection has a groove arranged on an outer circumference of the projection in which an O-ring is arranged, wherein the piston radially encompasses the projection, wherein the piston has a locking groove on its inner circumferential surface, and wherein the transmission element is connected to the piston via the O-ring arranged in the grooves.

[0011] In an advantageous embodiment of the invention, it is provided that the outer diameter of the outer circumference of the projection is smaller than the inner circumference diameter of the piston in each axial region.

[0012] In an advantageous embodiment of the invention, the piston has a chamfer on the inner circumferential surface at one end. In an advantageous embodiment of the invention, the transmission element has a chamfer on the outer circumference of the projection.

[0013] In an advantageous embodiment of the invention, it is provided that the transmission element is connected to the first brake disc element (16) via a cooling structure provided on a rear side of the first brake disc element.

[0014] The axle component can be an axle drive unit, particularly an electric one, a differential, or a chassis component such as an axle carrier. In particular, compared to wet friction brakes, dry friction disc brake systems run hotter, and integrating the friction disc brake system into the axle component makes cooling by airflow impossible or insufficient. Therefore, thermal decoupling, especially of the piston, from the first brake element or the friction surfaces is desirable, which can be achieved particularly advantageously by the invention. This prevents undesirable, excessive heating of the piston and, consequently, of the hydraulic fluid, for example, resulting from braking, thus enabling particularly advantageous operation of the friction disc brake systems.For example, the transmission element is primarily interposed with the piston to achieve thermal decoupling of the piston, particularly from the friction surfaces, since the brake disc elements can reach temperatures of up to 800 degrees Celsius during braking. Decoupling the piston from the brake disc elements using the transmission element thermally protects the hydraulic fluid, also known as brake fluid. Because the transmission element increases in thickness radially (i.e., from the outside inwards along the friction disc brake assembly), a particularly high level of stability can be achieved in a space-saving and weight-efficient manner. In particular, a significantly greater thickness can be achieved at the force application point of the transmission element. Furthermore, an end cap contour can be used to achieve high heat capacity.

[0015] Since preferably the outer diameter of the outer circumference of the projection is smaller than the inner circumference diameter of the piston in every axial area, the transmission element and the piston are only in contact with each other via the O-ring, which enables good thermal decoupling.

[0016] By having the chamfer preferably on the inner circumferential surface of the piston head side, a safe, easy and in particular gentle installation of the O-ring can be achieved.

[0017] Since the transmission element preferably has the chamfer on the outer circumference of the projection, a particularly large distance to the piston can be achieved, resulting in particularly good thermal decoupling and easy assembly.

[0018] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0019] The drawing shows in: Fig. 1. Partially a schematic sectional view of an electric axle drive device of a motor vehicle, wherein a friction disc brake device is integrated into the electric axle drive device; Fig. 2. Partially a schematic longitudinal section view of the friction disc brake device; Fig. 3. Partially shown, another schematic longitudinal section view of the friction disc brake assembly; and Fig. 4. Partially shown is another schematic longitudinal section view of the friction disc brake assembly.

[0020] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0021] Fig. Figure 1 shows a partial schematic longitudinal sectional view of an electric axle drive unit 10 of a motor vehicle, which is also simply referred to as the vehicle and can be driven, in particular purely electrically, by means of the electric axle drive unit 10. For example, the electric axle drive unit 10, also referred to as the electric drive module, has a vehicle axle of the motor vehicle. For example, the motor vehicle has exactly two vehicle axles, namely the aforementioned vehicle axle as the first vehicle axle and a second vehicle axle. The vehicle axles are arranged consecutively in the longitudinal direction of the motor vehicle and thus one behind the other. Each vehicle axle has exactly two vehicle wheels. The respective vehicle wheels of each vehicle axle are arranged on opposite sides of the motor vehicle in the transverse direction of the motor vehicle.The vehicle wheels of the motor vehicle are ground contact elements of the motor vehicle. Since, for example, the electric axle drive unit 10 comprises the first vehicle axle, the axle drive unit 10 also comprises the vehicle wheels of the first vehicle axle. For example, the vehicle wheels of the first vehicle axle can be driven electrically by means of the axle drive unit 10, and thus the motor vehicle can be driven electrically.

[0022] The axle drive unit 10 comprises a housing 12 and at least one electric machine (not visible in the figures), which is at least partially arranged in the housing 12. The electric machine has a stator and a rotor, which can be driven by means of the stator and is thus rotatable about a machine axis relative to the stator. The electric machine can provide drive torques via the rotor for, in particular, purely electric, driving of the vehicle wheels of the first vehicle axle. Furthermore, it is conceivable that at least or exactly one of the vehicle wheels of the first vehicle axle can be driven, in particular purely electric, by means of the electric machine and thus by means of the axle drive unit 10. When the vehicle wheels are mentioned below, unless otherwise specified, this refers to the vehicle wheels of the first vehicle axle.When the vehicle wheel is mentioned below, unless otherwise specified, this refers to the vehicle wheel that can be driven by means of the axle drive unit 10, that is, by means of the electric machine of the axle drive unit 10. Thus, the vehicle wheel can be driven by the rotor and is therefore rotatable about a wheel axis relative to the housing 12.

[0023] For example, the axle drive unit 10 has a gearbox, which can be at least partially arranged in the housing 12. The preceding and following descriptions of the vehicle wheel can readily be applied to the vehicle wheels of the first vehicle axle and vice versa. For example, the vehicle wheel can be driven by the rotor and thus by the electric machine via the gearbox. As will be explained in more detail below, a braking device 14 is integrated into the axle drive unit 10, by means of which braking can be effected, i.e., carried out. During or through braking, the vehicle wheel can be braked with respect to a rotation about the wheel axis and relative to the housing 12, i.e., its rotation can be stopped.In other words, when braking is carried out by means of the braking device 14, the vehicle wheel is thereby braked with respect to its rotation about the wheel axis and relative to the housing 12, i.e., slowed down, or at least decelerated. The braking device 14 is a friction disc brake device, as will be explained in more detail below. The braking device 14 has a first brake disc element 16 with a first friction surface 18. Furthermore, the braking device 14 has a second brake disc element 20 with a second friction surface 22 and a pad element arranged axially between the brake disc elements 16 and 20. The pad element 17 has a first pad surface 19, which can be brought into frictional contact with the first friction surface 18, and a second pad surface 21, which can be brought into frictional contact with the second friction surface 22.The axle drive assembly 10 has a shaft 24, for example, designed as a cardan shaft, wherein at least a part of the shaft 24 is rotatable about an axis of rotation 26 relative to the housing 12 and also relative to the brake disc element 16, and thus relative to the friction surface 18. An axial direction of the brake assembly 14 coincides with the axis of rotation 26 and is illustrated by a double arrow 28. The brake assembly 14, whose radial direction is perpendicular to the axial direction of the brake assembly 14 and thus perpendicular to the axis of rotation 26, and is illustrated by a double arrow 32, also has a piston 34, which is also referred to as an actuating piston. When the axial direction is mentioned before and after, this refers, unless otherwise specified, to the axial direction of the brake assembly 14.When the radial direction is mentioned before and below, unless otherwise specified, this refers to the radial direction of the braking device 14, whose circumferential direction is around the axial direction and thus around the axis of rotation 26, and lies in an imaginary plane perpendicular to the axial direction and thus perpendicular to the axis of rotation 26. The circumferential direction of the braking device 14 is illustrated by a double arrow 36. The term "axial" refers to the axial direction, and the term "radial" refers to the radial direction.

[0024] The aforementioned part of the shaft 24, which is designed, for example, as a driveshaft and is rotatable about the axis of rotation 26 relative to the housing 12 and relative to the brake disc element 16, is designated 38 and is, for example, a first shaft section of the driveshaft. The driveshaft, which is designed, for example, as a constant velocity joint, has a joint 40 through which the first shaft section (section 38) is articulated to a second shaft section of the driveshaft (not shown in the figures) and, in particular, is coupled for torque transmission.The friction disc element 17, and thus the friction surfaces 19 and 21, are connected, in particular permanently, to torque-transmitting and rotationally fixed, at least to the part of the shaft 24, so that at least the part 38 of the shaft 24 and the friction disc element 17, and thus the friction surfaces 19 and 21, are rotatable about the axis of rotation 26 relative to the housing 12 and also relative to the brake disc element 16, and thus relative to the friction surface 18. For example, the second shaft section is coupled, or can be coupled, to the vehicle wheel in a torque-transmitting and rotationally fixed manner. Thus, the second shaft section can rotate with the vehicle wheel about the wheel's axis of rotation relative to the housing 12.

[0025] At least part 38 of the shaft 24 and thus the lining disc element 17 are, especially when the vehicle wheel is rotated around the wheel axis relative to the housing 12, rotatable with the vehicle wheel and thus rotatable around the axis 26 relative to the housing 12 and also relative to the brake disc element 16.

[0026] The electric machine can drive the shaft 24 and the friction disc element 17 via its rotor, and in particular by means of the respective drive torque, thereby rotating at least part 38 of the shaft 24 and the friction disc element 17 about the axis of rotation 26 relative to the housing 12. As will be explained in more detail below, the braking device 14 can brake the shaft 24 and, via this, the vehicle wheel with respect to their respective rotations relative to the housing 12.

[0027] At the in Fig. In the embodiment shown in Figure 1, the brake device 14 has a second brake disc element 20 with a second friction surface 22. The brake disc elements 16 and 20, and thus the friction surfaces 18 and 22, are at least indirectly rotationally fixed to the housing 12 and are therefore not rotatable about the axis of rotation 26 relative to the housing 12. The brake disc element 16 is axially displaceable relative to the housing 12 and preferably also relative to the brake disc element 20. For this purpose, a toothed section 48 is provided. The toothed section 48 allows axial displacements of the brake disc element 16 relative to the housing 12.The friction disc element 17 is connected to the part 38 in a torque-transmitting manner, and in particular in a rotationally fixed manner, by means of the toothing 46, and is thereby rotatable with the part 38 about the axis of rotation 26 relative to the housing 12. In particular, the piston 34 is axially movable, and in particular displaceable, relative to the housing 12 and especially relative to the friction disc element 17 and the brake disc element 20. The brake disc element 20 is rotationally fixed to the housing 12 and thus cannot be rotated about the axis of rotation 26 relative to the housing 12. Furthermore, it is preferably provided that the brake disc element 20 is axially fixed to the housing 12 and thus cannot be moved axially relative to the housing 12. The brake disc element 16 is preferably rotationally fixed and axially displaceable to the housing 12 and thus cannot be rotated about the axis of rotation 26 relative to the housing 12. For this purpose, for example, a second toothing 48 is provided.Thus, for example, the brake disc element 16 is connected to the housing 12 in a rotationally fixed manner by means of the toothing 48, whereby the toothing 48 allows axial displacements and displacements relative to the housing 12, i.e. translational movements of the brake disc element 16.

[0028] In this case, the piston 34 is designed as an annular piston. The piston 34 can be actuated, particularly directly, with hydraulic fluid and thus hydraulically actuated. For this purpose, a hydraulic channel 50, through which the hydraulic fluid flows, runs within the housing 12. Furthermore, an actuation chamber 52, also referred to as the working chamber, is provided, which is partially and directly bounded by the housing 12 and partially and directly by the piston 34. The hydraulic channel 50 opens into the actuation chamber 52. This allows the hydraulic fluid flowing through the hydraulic channel 50 to be introduced into the actuation chamber 52, thereby enabling the piston 34 to be actuated, particularly directly, with the hydraulic fluid.By hydraulically actuating the piston 34, the piston 34 is axially movable, i.e. in the axial direction relative to the housing 12 and, for example, also relative to the brake disc elements 16, 20 and the pad disc element 17, i.e., displaceable.

[0029] The brake assembly 14 also includes a transmission element 54, which is also referred to as an actuating element and is designed separately from the piston 34 and separately from the brake disc elements 16, 20 and the pad element 17. By means of the hydraulic actuation of the piston 34 described above, the transmission element 54 can be actuated by means of the piston 34 and is thereby axially movable and relative to the housing 12, i.e., displaceable. This means that the transmission element 54 is axially movable, i.e., displaceable, relative to the housing 12 and, for example, also relative to the brake disc element 20 and, in particular, relative to the pad element 17.By actuating the transmission element 54, the first brake disc element 16 can be actuated by means of the transmission element 54 and thereby moved axially and relative to the housing 12 and preferably also relative to the pad disc element 17 and the brake disc element 20, i.e., displaced. For this purpose, the transmission element 54 is, for example, at least indirectly axially rigidly connected to the brake disc element 16, so that, for example, axially directed relative movements between the first brake disc element 16 and the transmission element 54 are prevented.It can be seen that by hydraulically actuating the piston 34, the transmission element 54 and, via the transmission element 54, the first brake disc element 16 can be actuated. This causes the friction surface 18 to come into frictional contact with the pad surface 19 and the friction surface 22 with the pad surface 21, thus braking the part 38 and therefore the vehicle wheel relative to the housing 12. For example, the first friction surface 18 is first moved axially towards the pad surface 19, resulting in direct frictional contact. Simultaneously, the pad surface 21 is moved axially towards the friction surface 22, resulting in direct frictional contact.

[0030] It can be seen that the friction surface 18 and the lining surface 19 are axially oriented towards each other, and the friction surface 22 and the lining surface 21 are axially oriented towards each other.

[0031] A cooling structure 56 is arranged on the rear side R of the brake disc element 16, which faces axially away from the friction surface 18. The transmission element 54, for example, is connected to the brake disc element 16 via this cooling structure, in particular such that axial relative movements between the transmission element 54 and the first brake disc element 16 are prevented. The cooling structure 56 has at least one or more cooling channels, which are also referred to as first cooling channels. A preferably liquid coolant can flow through each first cooling channel, thereby advantageously cooling the brake disc element 16 and, for example, also the transmission element 54.

[0032] At the in Fig. In the embodiment shown in Figure 1, a second cooling structure 58 is provided on a wide rear side R2 of the brake disc element 20, facing axially away from the friction surface 22. The second cooling structure 58 has, for example, at least one or more second cooling channels. The respective second cooling channel can be permeated by the coolant mentioned above, thereby advantageously cooling the second brake disc element 20.

[0033] Shaft 24 is, for example, an output shaft of the axle drive unit 10. It is conceivable that the rotor and / or shaft 24 are arranged coaxially with the vehicle wheel, so that, for example, the machine axis of rotation and / or the axis of rotation 26 coincide with the wheel axis of rotation. In particular, the axle drive unit 10 can drive the vehicle wheel at its end face via shaft 24, which functions as a drive shaft.

[0034] The housing 12 comprises a first housing part 60 and a second housing part 62, wherein the housing part 62 is, for example, a first cover of the housing 12. The first cover is also referred to as a side cover. Considering only the housing part 60, the housing part 60 has a housing opening 64, which is at least partially closed by the housing part 62. The housing parts 60 and 62 are formed separately from one another and are connected to each other at least indirectly, and in particular directly, in such a way that relative movements between the housing parts 60 and 62 are prevented. In particular, the side cover is arranged on an end face, in particular an axial face, of the housing part 60. The shaft 24 is supported in the side cover, in this case by means of at least one bearing 66 designed as a rolling bearing, which in this case is a ball bearing.The shaft 24, designed as an output shaft, therefore runs centered on the side cover, in particular such that at least part 38 runs centered on the side cover. In particular, at least part 38 is rotatably mounted in and on the housing part 62 (side cover) by means of the bearing 66, that is, rotatably mounted about the axis of rotation 26 relative to the housing 12.

[0035] The friction disc element 17 has a friction disc carrier disc, also referred to simply as a carrier disc, which is, for example, a base body of the friction disc element 17. The carrier disc is arranged centrally on the toothing 46 and is thus axially displaceable relative to the shaft 24 and relative to the housing 12, but torque-transmitting, in particular rotationally fixed, connected to the part 38, in particular the shaft 24.

[0036] It is conceivable that the friction surface 22 is an outer surface of the side cover (housing part 62). Thus, it would be conceivable that the brake disc element 22 is formed as a single unit with the side cover. In the case of the Fig. In the embodiment shown in Figure 1, the brake disc element 20 is designed separately from the side cover and connected to the side cover (housing part 62), in particular in such a way that relative movements between the side cover and the brake disc element 20 are prevented. Since, for example, the cooling structure 58 is provided here, the brake disc element 20 is a cooled, in particular liquid-cooled, brake disc.

[0037] For example, the respective cooling structure 56, 58 is formed by or designed as a respective cooling plate. Since the aforementioned, preferably liquid, coolant can flow through the respective cooling channel and thus through the respective cooling plate, the cooling plate is a cooled, in particular liquid-cooled, cooling plate. The coolant can advantageously absorb heat via the respective cooling structure 56, 58, which is generated during the aforementioned braking process, also referred to as braking, by the friction surface 18, 22 rubbing against a lining surface 19 and 21.

[0038] The brake disc element 16 is a friction disc that is connected to the housing 12, particularly to the side cover, in a torque-transmitting and, in particular, rotationally fixed manner, but is axially displaceable relative to the housing 12 and thus relative to the side cover. In particular, the brake disc element 16 is centered relative to the side cover by means of the toothing 48.

[0039] The side cover forms, that is, directly defines, a receiving space 68, also referred to as an interior. For example, the receiving space 68 is annular. The brake disc elements 16 and 20, as well as the pad element 17, are arranged in the receiving space 68, which is formed, that is, defined, by the side cover. The side cover at least partially closes the housing opening 64 and thus an interior space 70 of the housing 12, also referred to as a housing chamber, to the outside, i.e., towards the surroundings 72 of the axle drive unit 10. The interior space 70 is formed, that is, directly defined, by the housing part 60, with, for example, the transmission and the electric motor each being at least partially arranged in the interior space 70.

[0040] The side cover is an intermediate cover arranged axially between housing part 60 and a third housing part 74 of the housing 12. Housing part 74 is separate from housing parts 60 and 62 and is connected to them at least indirectly. Housing part 74 is connected to the side cover at least indirectly, in particular such that relative movements between the side cover and housing part 74 are prevented. Specifically, housing parts 60, 62, and 74 are connected to each other in pairs such that relative movements between them are prevented when considered as a pair. Housing part 74 is also referred to as the end cover. Looking at the side cover alone, it has an opening 76 through which the receiving chamber 68 is open to the outside and thus to the surroundings 72.The end cap at least partially closes off the cover opening 76 and thus the receiving chamber 68 to the outside and therefore to the surroundings 72. It is evident that the piston 34 is at least partially located within the end cap. In this case, the piston 34 is at least partially radially arranged within the end cap. Furthermore, the piston 34 is arranged to overlap the end cap axially, at least partially. It is also evident that the hydraulic channel 50 runs within the end cap, and that the actuation chamber 52 is directly bounded partly by the piston 34 and partly by the end cap.

[0041] It is also evident that the end cap is arranged radially overlapping with the brake disc elements 20, 16 and the pad disc element 17, so that the brake disc elements 16, 20 and the pad disc element 17 are at least partially covered axially to the environment 72 by the end cap.

[0042] By hydraulically actuating the piston 34, the hydraulically actuated piston 34 presses axially against the transmission element 54 and thus, via this element, indirectly against the brake disc element 16. The transmission element 54 is frustoconical in shape to achieve advantageous force transmission. Preferably, the transmission element 54 is made of stainless steel or ceramic to prevent excessive heat transfer from the transmission element 54 to the piston 34. The aforementioned stainless steel and ceramic exhibit lower thermal conductivity compared to conventional steel or aluminum.

[0043] To avoid excessively high temperatures of piston 34 and the hydraulic fluid, it is particularly well shown that Fig. 2 and Fig. As can be seen in Figure 3, the transmission element 54 has a first groove 78 and the piston 34 has a second groove 80. An intermediate element 82 is provided, formed separately from the transmission element 54 and the piston 34 and arranged in the grooves 78 and 80, by means of which the transmission element 54 and the piston 34 are connected. The intermediate element 82 is a thermally separating compensating element by means of which the piston 34 can be thermally decoupled from the transmission element 54 and thus from the friction surface 18, which is particularly advantageous. In the embodiment shown in the figures, the intermediate element 82 is formed from an elastomer and is designed as an O-ring, which makes the intermediate element 82 elastically deformable, in particular with rubber elasticity.For example, the inner diameter of the piston 34 at the location of the groove 80 is larger than the outer diameter of the transmission element 54 at that location by a radial offset that is the maximum possible due to tolerances. To prevent excessive vibrations between the piston 34 and the transmission element 54, the intermediate element 82 bridges a radial gap located at that point between the transmission element 54 and the piston 34. Furthermore, the intermediate element 82 allows the piston 34 and the transmission element 54 to be joined together in a pre-assembly step.

[0044] Out of Fig. 2 and Fig. As can be seen particularly well in Figure 3, the transmission element 54 has a projection 84 extending axially from a base region G of the transmission element 54 and away from the brake disc element 16, in the outer circumferential surface M1 of which the first groove 78 is formed. The piston 34 has an inner circumferential surface M2 facing radially towards the outer circumferential surface M1, which surrounds the outer circumferential surface M1 and the first groove 78 in the circumferential direction. The second groove 80 is formed in the inner circumferential surface M2. Furthermore, it is provided that a chamfer F of the inner circumferential surface M2, widening axially towards the base region G, adjoins the second groove 80 at an end E of the piston 34 facing axially towards the base region G.

[0045] Fig. Figure 2 shows an unactuated state of piston 34. Fig. Figure 3 shows the piston 34 in an actuated state, which is hydraulically actuated in this state. This means that the Fig. Figure 3 shows the actuated state of piston 34 resulting from the previously described hydraulic actuation of piston 34. Piston 34 can be moved from the actuated state to the unactuated state, for example, by ending the hydraulic actuation of piston 34. Fig. 2 and Fig. Figure 3 shows that, by hydraulically actuating the piston 34, the piston 34 is axially displaceable and thus movable relative to the housing 12 and relative to the transmission element 54, and in the direction of the friction surfaces 18 and 22, under elastic deformation of the intermediate element 82. This allows an end face SF of the piston 34 to be displaceable and thus movable in direct contact with a corresponding support surface AF of the transmission element 54. This means that, in the actuated state of the piston 34, the end face SF rests directly against the corresponding end surface AF, enabling a particularly advantageous force transmission between the piston 34 and the transmission element 54. In the actuated state of the piston 34, the intermediate element 82 is elastically deformed to a greater extent than in the unactuated state of the piston 34.When the hydraulic actuation of the piston 34 is terminated, this allows at least partial elastic relaxation of the intermediate element 82, which is also referred to as an expansion effect. In other words, when the hydraulic actuation of the piston 34 is terminated to release the actuated state of the piston 34, the intermediate element 82, which was initially elastically deformed in the actuated state of the piston 34, can at least partially relax and thus spring back. This allows the piston 34, and therefore its end face SF, to be axially displaced and thus moved away from the transmission element 54 and the support surface AF. As a result, in the unactuated state of the piston 34, the end face SF is completely separated from the support surface AF.Preferably, it is provided that in the unactuated state of the piston 34 the piston 34 is completely spaced away from the transmission element 54 which is formed separately from the piston 34, thereby avoiding an undesirable, excessive transfer of heat from the transmission element 54 to the piston 34.

[0046] The piston 34 and the transmission element 54 are preferably made of a metallic material. Thus, when the brake device 14 is actuated, the piston 34 presses with its axial end face SF against the support surface AF and thus against the transmission element 54, creating direct metallic contact between the piston 34 and the transmission element 54. After the brake is released, i.e., after the hydraulic actuation of the piston 34 has ceased, the intermediate element 82, which is elastically deformed at least or exclusively axially when the piston 34 is actuated, ensures that the piston 34 and the transmission element 54 move axially away from each other and thus separate at least slightly, such that the end face SF and the support surface AF are pushed axially away from each other and thus, in particular, completely separated from each other.This prevents excessive heat transfer from the hot transmission element 54 to the piston 34.

[0047] The brake assembly 14 has a spring element 85. The spring element 85 is designed as a solid body and thus as a mechanical spring element, i.e., as a mechanical spring. In the embodiment shown in the figures, the spring element 85 is designed as an annular cup spring. By hydraulically actuating the piston 34, the spring element 85 is elastically deformable, so that in the actuated state of the piston 34, the spring element 85 provides a spring force. By means of the spring force of the spring element 85, the brake disc element 20 is axially displaceable relative to the housing 12 as a result of the cessation of the hydraulic actuation of the piston 34, in particular into its initial position, whereby the frictional contact between the friction surface 18 and the lining surface 19 and also between the friction surface 22 and the lining surface 21 can be broken or is broken.This releases the brake assembly 14, also referred to simply as the brake, in particular completely. In this case, the spring element 85 is attached to a toothed carrier ring. During braking, i.e., during the hydraulic actuation of the piston 34, an outer, in particular the outermost, area of ​​the spring element 85 is elastically deformed, thereby providing the spring force to return the brake disc element 16, in particular to its initial position. If, for example, the friction linings wear down, the spring element 85, in addition to its elastic deformation on the toothed carrier ring, is displaced axially towards the electric motor, i.e., towards the interior 70. As a result, the brake disc element 16 is always only returned by the elastic distance. Even with wear of the friction linings, the brake clearance remains at least essentially constant.

[0048] It is evident that the intermediate element 82, which functions or is designed as a decoupling element, enables the piston 34, designed as a ring brake piston, and the transmission element 54, designed here as a pressure plate, to be joined together to form an assembly unit in a simple and cost-effective manner. During the joining process of the transmission element 54 with the piston 34, the intermediate element 82 is radially compressed by means of the chamfer F of the piston 34 until the intermediate element 82 engages, or snaps into, the groove 80 of the piston 34, which is designed here as a detent groove. In the state of the intermediate element 82 being arranged in the groove 80, it is elastically deformed, particularly radially, and thus pre-stressed. For example, the groove 78 is designed as an O-ring groove.The intermediate element 82, which is partially arranged in the grooves 78 and 80, results in a quasi-positive locking connection between the transmission element 54 and the piston 34. Very high forces are required to separate the transmission element 54 and the piston 34.

[0049] By introducing hydraulic fluid, for example oil, into the actuation chamber 52, a pressure, particularly oil pressure, is generated in the actuation chamber 52, which is, for example, an annular space. This pressure is caused by the hydraulic fluid. As a result, the piston 34 moves, particularly axially, towards the transmission element 54. During this movement, the intermediate element 82 is elastically deformed and thereby compressed and overpressed, so that the end face SF comes into direct contact with the support surface AF. An actuating force resulting from the pressure is then transmitted by the piston 34 directly, via the direct contact between the support surface AF and the end face SF, to the transmission element 54 and subsequently to the brake disc elements 16, 20 and the pad element 17.By ceasing the hydraulic actuation of the piston 34, also known as releasing the brake, the pressure in the actuation chamber 52 drops again, causing the piston 34 to move away from the transmission element 54. This allows the intermediate element 82 to expand again. To ensure, for example, that the intermediate element 82 expands not only radially but also axially, a shoulder 86, also referred to as a shoulder surface, is arranged in the groove 78. This shoulder is formed, for example, by the groove base of the groove 78. The shoulder 86 is conical and thus follows an imaginary cone. The shoulder 86 causes the intermediate element 82 to be pushed away from the transmission element 54 or the support surface AF when the intermediate element 82 relaxes and thus expands.Since the intermediate element 82 is supported in the groove 80 of the piston 34, which is designed, for example, as a locking groove, the piston 34 and the transmission element 54 are separated from each other, especially when the intermediate element 82 relaxes and thus expands, and by means of the intermediate element 82 the piston 34 and the transmission element 54 can be advantageously thermally isolated from each other, i.e. decoupled.

[0050] Finally, it shows Fig.4. The axle drive assembly 10 and, in particular, the friction disc brake assembly (brake assembly 14) are shown in partial schematic longitudinal section. The groove 78 of the transmission element 54 is, for example, designed as an O-ring groove in which the present intermediate element 82, designed as an O-ring, is arranged. For example, the intermediate element 82 is made of an elastomer, namely rubber, and is therefore deformable, in particular elastically deformable, and most especially rubber-elastically deformable. A snap-ring connection is formed or can be formed by means of the intermediate element 82, since the intermediate element 82 is, for example, designed as a ring by means of which the piston 34 is coupled to the transmission element 54. The intermediate element 82 can be used for offset compensation and for thermal separation of the piston 34 from the brake disc element 16.Piston ring grooves are designated 88 and 90, the respective piston ring grooves 88 and 90 being formed in the housing part 74, also referred to as the end cap. A centering element between the piston 34 and the transmission element 54 is designated Z, wherein the piston 34 is aligned, in particular centered, relative to the transmission element 54 by means of the centering element Z. Unmachined inner surfaces of the transmission element 54 are designated 92. In the axial direction of the axle drive assembly 10 and thus of the brake assembly 14, a chamfer 94 of the transmission element 54, also referred to as a ramp, is enclosed on a side of the groove 78 facing away from the brake disc element 16 in the axial direction.The chamfer 94 is frustoconical and thus formed in the shape of a truncated cone, which tapers in an axial direction extending away from the brake disc element 16 from the groove 78, or widens towards the groove 78. The chamfer 94 makes it particularly easy to mount the intermediate element 82 in the groove 78. For this purpose, the intermediate element 82 is moved axially relative to the transmission element 54 and thus along the chamfer 94. This stretches the intermediate element 82 radially, in particular until it overlaps the groove 78 and can then spring back radially inwards and snap into the groove 78.

[0051] The transmission element 54 is made of stainless steel, for example, because stainless steel has an advantageously low thermal conductivity, especially compared to conventional heat-treated steel. This prevents excessive heat conduction from the hot friction surfaces to the hydraulic fluid. The centering element Z has a short axial length of less than one millimeter to minimize the contact area between the piston 34 and the transmission element 54. This allows for continuous thermal decoupling. This centering element Z also preferably has a clearance of approximately 0.2 millimeters to minimize heat transfer and allow angular movement between the piston 34 and the transmission element 54. The unmachined inner surfaces 92 are radial inner surfaces of the transmission element 54 and are left unmachined to save costs. Reference symbol list 10 electric axle drive units 12 cases 14 Brake system 16 first brake disc element 18 first friction surface 17 Padding disc element 19 first surface area 21 second surface area 20 second brake disc element 22 second friction surface 24 wave 26 axis of rotation 28 Double Arrow 32 Double Arrow 34 pistons 36 Double Arrow Part 38 40 joint 46 gear teeth 48 teeth 50 hydraulic channel 52 Activity area 54 Transmission element 56 Cooling structure 58 Cooling structure 60 first housing part 62 second housing part 64 Case opening 66 warehouses 68 Recording room 70 Interior 72 surroundings 74 third housing part 76 lid openings 78 first groove 80 second groove 82 Intermediate element 84 Cantilever 85 spring element 86 Shoulder 88 Piston ring groove 90 Piston ring groove 92 interior surface area 94th phase AF support surface F phase G Basic area M1 outer circumferential surface M2 inner circumferential surface SF front surface Z-centering QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 118 503 A1

[0002]

Claims

[1] Dry-running friction disc brake device (14) for a motor vehicle, comprising at least one first brake disc element (16) having at least one first friction surface (18), at least one second brake disc element (20) having at least one second friction surface (22), a pad disc element (17) arranged between the brake disc elements (16, 20), a piston (34) designed as an annular piston which can be pressurized with hydraulic fluid and thereby hydraulically actuated, and an annular disc-shaped transmission element (54) arranged between the piston (34) and the first brake disc element (16), which has an axially directed projection (84) on its inner circumference, wherein: - by means of the piston (34) by hydraulic actuation of the piston (34) the transmission element (54) and via the transmission element (54) the first brake disc element (16) can be actuated, whereby the friction surfaces (18, 22) can be brought into frictional contact with the pad disc element to effect braking, - the cantilever (84) is operatively connected to the piston (34) via an outer surface of the cantilever (84); and - the axial extension of the transmission element (54) increases from radially outside to radially inside on a side facing away from the first brake disc element (16). [2] Friction disc brake device (14) according to claim 1, characterized by, that the projection (84) has a groove (78) arranged on an outer circumference of the projection (84) in which an O-ring (82) is arranged, wherein the piston (34) radially surrounds the projection (84), wherein the piston (34) has a locking groove (80) on its inner circumferential surface, and wherein the transmission element (54) is connected to the piston (34) via the O-ring (82) arranged in the grooves (78, 80). [3] Friction disc brake device (14) according to claim 1 or 2, characterized by , that an outer diameter of the outer circumference of the projection (84) is smaller in each axial region than an inner circumference diameter of the piston (34). [4] Friction disc brake device (14) according to one of the preceding claims, characterized by , that the piston (34) has a chamfer (F) on the inner circumferential surface at one head side. [5] Friction disc brake device (14) according to one of the preceding claims, characterized by, that the transmission element (54) has a chamfer (94) on the outer circumference of the projection (84). [6] Friction disc brake device (14) according to one of the preceding claims, characterized by , that the transmission element (54) is connected to the first brake disc element (16) via a cooling structure (56) provided on a rear side (R) of the first brake disc element (16).

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