Braking system for a motor vehicle

Abstract

The invention relates to a braking device (14) for a motor vehicle, comprising a housing (62, 74) and a friction disc (20) arranged axially between a first counter-rotating disc (42) and a second counter-rotating disc (16) of the braking device (14), wherein the friction disc (20) is axially displaceable relative to the housing (62, 74) and relative to the counter-rotating discs (42, 16). The first counter-rotating disc (42) is rotationally fixed and axially fixed to the housing (62, 74). The second counter-rotating disc (16) is rotationally fixed to the housing (62, 74) and axially displaceable relative to the housing (62, 74), relative to the friction disc (20), and relative to the first counter-rotating disc (42). On a side (R) of the second counter-rotating disc (16) facing away axially from the friction disc (20) a housing cover (74) is arranged, through which at least two bolts (88) are passed.

Description

[0001] The invention relates to a braking device for a motor vehicle.

[0002] DE 10 2022 113 216 A1 describes a braking device for a vehicle with two reset devices as known.

[0003] The object of the present invention is to create a particularly advantageous braking device for a motor vehicle.

[0004] This problem is solved by a braking 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 braking device, also referred to simply as a brake, for a motor vehicle, also referred to simply as a vehicle. In particular, the braking device is integrated into a housing of the motor vehicle, especially an axle drive unit of the motor vehicle. The braking device comprises a housing assembly, which is, for example, part of the housing. The braking device includes a friction disc, which is arranged axially between a first counter-rotating disc of the braking device and a second counter-rotating disc of the braking device. The friction disc is axially displaceable relative to the housing assembly and relative to the counter-rotating discs. For example, the friction disc is rotatable about an axis of rotation relative to the counter-rotating discs and relative to the housing assembly of the braking device, the axial direction of which coincides with that of the axis of rotation."Axial" refers to the axial direction of the braking device, whose radial direction is perpendicular to the axial direction and thus perpendicular to the axis of rotation. "Radial" refers to the radial direction. The first counter-rotating disc is fixed to the housing and therefore cannot rotate about the axis of rotation relative to the housing. Furthermore, the first counter-rotating disc is axially fixed to the housing and therefore cannot move axially relative to the housing. The second counter-rotating disc is fixed to the housing and therefore cannot rotate about the axis of rotation relative to the housing. Furthermore, the second counter-rotating disc is axially displaceable relative to the housing, relative to the friction disc, and relative to the first counter-rotating disc. The friction disc, for example, has a first friction surface and a second friction surface.The first counter-rotating disc, for example, has a third friction surface. The second counter-rotating disc, for example, has a fourth friction surface. For example, the first friction surface and the third friction surface are axially oriented towards each other, and for example, the second friction surface and the fourth friction surface are axially oriented towards each other. For example, the second counter-rotating disc can be actuated, particularly hydraulically, by actuating the brake device, and thereby moved axially towards the friction disc and the first counter-rotating disc, whereby, for example, the first friction surface can be brought into mutual and, in particular, direct frictional contact with the third friction surface, and the second friction surface with the fourth friction surface.This allows, for example, the friction disc to be slowed down, i.e., braked, with respect to rotation about the axis of rotation relative to the housing and relative to the counter-rotating discs, thereby braking the entire vehicle. For example, in its fully manufactured state, the vehicle has at least one wheel, which is, for example, a ground contact element by which the vehicle can be supported or is supported downwards against a ground in the vertical direction. It is conceivable that the friction disc is connected to the wheel in a torque-transmitting manner, particularly in a rotationally fixed manner. The vehicle wheel is rotatable about a wheel axis relative to the housing.Thus, for example, when the vehicle wheel rotates around its axis of rotation relative to the housing, the friction disc rotates with the vehicle wheel and is therefore rotatable around its axis of rotation relative to the counter-rotating discs or relative to the housing. By actuating the brake, the friction disc can be used to brake the vehicle wheel with respect to its rotation around its axis of rotation relative to the housing, i.e., to slow it down, thereby at least slowing down the vehicle as a whole.

[0006] A housing cover, which can also be called an end cover and may be designed as such, is arranged on a side of the second counter-rotating disc facing away from the friction disc. At least two bolts pass through the housing cover, each bolt being axially fixed to the second counter-rotating disc and thus axially movable with the second counter-rotating disc relative to the housing assembly, the friction disc, and the first counter-rotating disc. A nut is screwed onto each bolt, specifically on an outer surface of the housing cover facing away from the second counter-rotating disc. A return spring is arranged on each nut, in particular such that the return spring is positioned axially between the nut and the housing cover, and especially on the outer surface.Thus, the second counter-rotating disc, which is axially displaceable relative to the housing cover, can be supported axially on the return spring via the bolt and nut, and axially on the housing cover via the return spring. The housing cover is an integral part of the housing assembly. By actuating the brake assembly, particularly hydraulically, the second counter-rotating disc is moved axially relative to the housing assembly, such that the second counter-rotating disc is moved axially towards the friction disc and the first counter-rotating disc, and axially away from the housing cover. Since the bolt and, via the bolt, the nut are moved axially relative to the housing cover along with the second counter-rotating disc, the return spring, located axially between the nut and the housing cover, is tensioned, thereby providing a restoring force.The restoring force acts axially via the nut and bolt on the second counter-rotating disc and can thus reset the second counter-rotating disc, thereby moving it axially away from the friction disc and the first counter-rotating disc relative to the housing assembly, especially when the braking device is no longer actuated.

[0007] In an advantageous embodiment of the invention, it is provided that on the side of the second counter-rotating disc facing away from the axial friction disc, a cooling chamber through which a coolant can flow is arranged between the housing cover and the second counter-rotating disc, wherein the respective bolt is hollow inside and thus has a respective cavity which is fluidically connected to the cooling chamber.

[0008] In an advantageous embodiment of the invention, it is provided that the respective return spring is designed as a disc spring.

[0009] In an advantageous embodiment of the invention, it is provided that the respective return spring rests against the respective nut on one side and against the housing cover on the other, both in the actuated state and in the unactuated state of the brake device.

[0010] Preferably, the return spring is pre-tensioned in both the unactuated and actuated states of the brake device, thus providing the aforementioned spring force. In this way, the return spring, for example designed as a disc spring, performs a sealing function by exerting an axial pressure against the respective nut and the end cap through its axial spring force. This pressure creates a dust-tight seal between the interior space containing the brake device and the surrounding environment. The interior space is formed, for example, and particularly directly, by an intermediate cover of the housing assembly, such that the brake device is located within and thus integrated into this intermediate cover.The housing cover and the intermediate cover are, for example, designed separately from each other and connected to each other at least indirectly, in particular directly, in such a way that relative movements between the intermediate cover and the housing cover are prevented.

[0011] The second counter-rotating disc can be cooled by means of the preferably liquid coolant, whereby, for example, the coolant can be introduced into the cooling chamber via one of the bolts and discharged from the cooling chamber via the other bolt. This allows for a particularly advantageous supply of coolant to the cooling chamber and a particularly advantageous discharge of coolant from the cooling chamber. In particular, coolant supply and discharge can be implemented with only a small number of parts and thus in a space-saving, weight-saving and cost-effective manner.

[0012] 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.

[0013] 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. A further schematic sectional view of the electric axle drive unit is shown in part.

[0014] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0015] 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.

[0016] 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.

[0017] 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. The axle drive device 10 has a shaft 24, for example, designed as a driveshaft, 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 direction 18.The brake disc element 20 of the brake assembly 14, whose axial direction coincides with the axis of rotation 26 and is illustrated by a double arrow 28, also has a third friction surface 30. 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 the actuating piston. When the axial direction is mentioned before and below, 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.

[0018] 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, 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 brake disc element 20, and thus the friction surfaces 22 and 30, are connected, in particular permanently, to the torque-transmitting, and in particular rotationally fixed, at least to the part of the shaft 24 such that at least the part 38 of the shaft 24 and the brake disc element 20, and thus the friction surfaces 22 and 30, 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 in particular 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.

[0019] At least part 38 of the shaft 24 and thus the brake disc element 20 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.

[0020] The electric machine can drive the shaft 24 and the brake disc element 20 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 brake disc element 20 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.

[0021] At the in Fig. In the embodiment shown in Figure 1, the brake device 14 has a third brake disc element 42 with a fourth friction surface 44. The brake disc elements 16 and 42, and thus the friction surfaces 18 and 44, 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 and, most preferably, also relative to the brake disc element 42. The brake disc element 20 is, for example, axially displaceable relative to the housing 12 and preferably also relative to the brake disc element 16 and, more preferably, relative to the brake disc element 42. For this purpose, a toothed connection 46 is provided, which is also referred to as a drive tooth.The brake disc element 20 is connected to the part 38 by means of the toothing 46 in a torque-transmitting manner, and in particular in a rotationally fixed manner, and is thus rotatable with the part 38 about the axis of rotation 26 relative to the housing 12. However, the toothing 46 allows axial displacements of the brake disc element 20 relative to the housing 12. For example, the piston 34 is also axially movable, and in particular displaceable, relative to the housing 12 and, for example, relative to the brake disc element 16, and preferably relative to the brake disc element 20 and relative to the brake disc element 42. The brake disc element 42 is rotationally fixed to the housing 12 and is therefore not rotatable 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 is therefore not axially movable relative to the housing 12.The brake disc element 16 is preferably connected to the housing 12 in a rotationally fixed manner and is therefore not rotatable about the axis of rotation 26 relative to the housing 12. For this purpose, for example, a second toothed section 48 is provided, which is referred to, for example, as a second drive tooth. Thus, for example, the brake disc element 16 is connected to the housing 12 in a rotationally fixed manner by means of the toothed section 48, whereby the toothed section 48, however, allows axial displacements and displacements relative to the housing 12, i.e., translational movements of the brake disc element 16.

[0022] 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 an axial direction relative to the housing 12 and, for example, also relative to the brake disc elements 16, 20 and 42, i.e., displaceable.

[0023] The brake assembly 14 also includes a transmission element 54, which is separate from the piston 34 and separate from the brake disc elements 16, 20, and 42, and which is also referred to as an actuating element. 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 brake disc element 42.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 brake disc element 20 and preferably relative to the brake disc element 42, 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 allows the friction surfaces 18 and 22, and in this case also the friction surfaces 30 and 44, to be brought into direct, mutual frictional contact, thus braking the part 38 and therefore the vehicle wheel relative to the housing 12. For example, the element 18 is first moved axially towards the friction surface 22 and moved into direct frictional contact with it. Furthermore, the friction surface 30 is moved axially towards the friction surface 44 and moved into direct frictional contact with it.

[0024] It can be seen that the friction surfaces 18 and 22 are axially oriented towards each other, and the friction surfaces 30 and 44 are axially oriented towards each other.

[0025] 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 and also from the friction surface 22. 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.

[0026] 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 42, which faces axially away from both the friction surface 44 and the friction surface 30. 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, for example, thereby advantageously cooling the third brake disc element 42.

[0027] 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.

[0028] 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.

[0029] In particular, at least part 38 is rotatable in and on the housing part 62 (side cover) by means of the bearing 66, i.e., rotatably mounted about the axis of rotation 26 relative to the housing 12.

[0030] The brake disc element 20 has a pad carrier disc, also referred to simply as a carrier disc, which is, for example, a base body of the brake disc element 20. The carrier disc is centered on the toothing 46 and is thus axially displaceable relative to the shaft 24 and the housing 12, but torque-transmitting, and in particular rotationally fixed, to the part 38, in particular the shaft 24. The carrier disc is provided, for example, with a first brake pad and a second brake pad, wherein, for example, the first brake pad forms the friction surface 22 and the second brake pad the friction surface 30. It can be seen that the friction surfaces 22 and 30 are arranged on axially opposite sides of the carrier disc, with the friction surfaces 22 and 30 pointing away from each other axially.

[0031] It is conceivable that the friction surface 44 is an outer surface of the side cover (housing part 62). Thus, it would be conceivable that the brake disc element 42 is formed as a single unit with the side cover. In the case of the Fig. In the embodiment shown in Figure 1, however, the brake disc element 42 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 42 are prevented. Since, for example, the cooling structure 58 is provided here, the brake disc element 42 is a cooled, in particular liquid-cooled, brake disc.

[0032] 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 surfaces 18, 22, 30 and 44 rubbing against each other.

[0033] 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.

[0034] The side cover forms, that is, directly delimits, a receiving space 68, also referred to as an interior. For example, the receiving space 68 is annular. The brake disc elements 16 and 22, and preferably also the brake disc element 42, are arranged in the receiving space 68, which is formed, that is, delimited, 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 an environment 72 of the axle drive unit 10. The interior space 70 is formed, that is, directly delimited, 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.

[0035] 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 at least partially axially.

[0036] It is also evident that the hydraulic channel 50 runs in the end cover, and that the actuation chamber 52 is partially directly limited by the piston 34 and partially by the end cover.

[0037] It is also evident that the end cap is arranged radially overlapping with the brake disc elements 20, 16 and 42, so that the brake disc elements 16, 20 and 42 are at least partially covered axially to the environment 72 by the end cap.

[0038] 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.

[0039] By bringing the friction surfaces 18 and 22 and the friction surfaces 30 and 44 into direct, friction-fit contact, a braking torque can be generated, thereby braking the shaft 24 and, via this, the vehicle wheel relative to the housing 12. This process generates braking heat.

[0040] 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 surfaces 18, 22, 30 and 44, 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.

[0041] 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 elements 16 and 20, 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.

[0042] 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. The piston 34 can be moved from the actuated state to the unactuated state, for example, by ending the hydraulic actuation of piston 34.

[0043] Out of 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.

[0044] 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.

[0045] 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 can be displaced axially 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, for example, the frictional contact between the friction surfaces 30 and 44 and, for example, also between the friction surfaces 18 and 22 can be broken or is broken.This releases or vents 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 20, in particular to its initial position. If, for example, the brake disc element 20 wears, 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 20 is always only returned by the elastic distance. Even if the brake disc element 20 wears, the brake clearance remains at least essentially constant.

[0046] 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.

[0047] 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 to the transmission element 54 via the direct contact between the support surface AF and the end face SF, and subsequently to the brake disc elements 16, 20, and 42.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 that widens axially towards the friction surfaces 18 and 22. 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.

[0048] It is evident that the housing 12 is or forms a housing assembly of the brake assembly 14. In particular, the intermediate cover (housing part 62) and the end cover (housing part 74) are or form a housing assembly of the brake assembly, which is arranged within the housing assembly. It is also evident that the brake disc element 20 is or forms a friction disc, which is arranged axially, i.e., in the axial direction of the brake assembly 14 and the axle drive assembly 10, between the brake disc elements 16 and 42. The respective brake disc elements 16 and 42 are or form a respective counter-rotating disc for the friction disc, such that the brake disc element 42 is a first counter-rotating disc and the brake disc element 16 is a second counter-rotating disc. The first counter-rotating disc is rotationally and axially fixed to the housing assembly, i.e., to the housing and, in particular, to the intermediate cover and the end cover.The second counter-rotating disc is rotationally fixed to the housing assembly and axially displaceable relative to the housing assembly, relative to the friction disc, and relative to the first counter-rotating disc. The friction disc is axially displaceable relative to the housing assembly and relative to the counter-rotating discs.

[0049] It can be seen that the housing part 74 is a housing cover, which is arranged on a side of the second counter-rotating disc facing away from the friction disc axially. This side of the second counter-rotating disc is, for example, the rear side R.

[0050] Out of Fig. Figure 1 shows that two bolts pass through the housing cover (housing part 74), one of which is designated 88. Each bolt 88 is axially connected to the second counter-rotating disc. A nut 90 is screwed directly onto each bolt 88, on an outer surface AS of the housing cover (housing part 74) facing away from the second counter-rotating disc. A return spring 92 is arranged on each nut 90, in this case such that the return spring 92 is positioned axially between the nut 90 and the housing cover (housing part 74).

[0051] The cooling structure 56 has at least one cooling chamber through which the aforementioned coolant flows, which is formed, for example, by the first cooling channel. Thus, the cooling chamber is arranged on the side facing away from the friction disc (rear side R) of the second counter-rotating disc, and is located axially between the housing cover (housing part 74) and the second counter-rotating disc. Each bolt 88 is hollow and therefore has a cavity within it that is fluidically connected to the cooling chamber. The coolant can flow through each cavity, so that, for example, the coolant can be introduced into the cooling chamber via one of the bolts 88, i.e., via the cavity of that bolt 88, and so that, for example, the coolant can be discharged from the cooling chamber via the other bolt 88, i.e., via the cavity of the other bolt 88.In this case, the respective return spring 92 is designed as a disc spring.

[0052] Depicted in Fig. 1 is also a bellows 94. For example, the respective bolt 88 is a respective screw bolt. A pressure equalization valve is designated 96.

[0053] Finally, it shows Fig. 4. Partially shown in a further schematic sectional view is the axle drive unit 10. Particularly well seen. Fig. 4. The bolt 88, the nut 90 and the return spring 92 are recognizable, as well as the one in Fig.4. The cavity of bolt 88 is designated 98. An arrow 100 illustrates the coolant and its flow through the cavity 98. The cooling chamber 102, also referred to as the coolant volume, is designed as a space for coolant and thus as a coolant chamber. A gear carrier supporting the toothing 46 is designated 104. A radial shaft seal is designated 106, whereby the housing part 74 is sealed against a sleeve 108, which is rotatable with part 38 of the shaft 24 and, for example, non-rotatably connected to it, by means of the radial shaft seal 106.

[0054] The axle drive unit 10 is an electric drive module whose output shafts are arranged coaxially with the driven vehicle wheels. The drive module drives the vehicle wheels, also referred to simply as wheels, at their ends by means of the output shafts, also referred to as drive shafts and driven shafts, one of which is shaft 24. The drive module has an intermediate cover, also referred to as a side cover, on its end face, in which shaft 24 is mounted. Shaft 24 therefore runs centered on the side cover. Shaft 24 has a joint 40 as a universal joint.

[0055] For example, the cavity 98 of the respective bolt 88 is formed by or as a bore and thus produced by machining. This allows the coolant to be introduced into the cooling chamber from the outside in a very simple manner.

[0056] The braking device 14 could alternatively be integrated into another component such as an axle drive, a differential drive or a chassis component such as an axle carrier.

[0057] The bolt 88, designed here as a screw bolt, is configured as a stepped flanged hose fitting and pressed into a base part of the second counter-rotating disc. The bolt 88 protrudes through the end cap via an opening located in the end cap. The return spring 92 also performs a sealing function by means of its axial pressure acting against the nut 90 on one side and the end cap on the other, thus sealing the receiving chamber 68 dust-tight to the outside. For example, the bolts 88 are arranged offset from each other by 81 degrees in the circumferential direction around the axis of rotation 26. Reference symbol list 10 electric axle drive units 12 cases 14 Brake system 16 first brake disc element 18 first friction surface 20 second brake disc element 22 second friction surface 24 wave 26 axis of rotation 28 Double Arrow 30 third friction surface 32 Double Arrow 34 pistons 36 Double Arrow Part 38 40 joint 42 third brake disc element 44 fourth friction surface 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 bolts 90 mother 92 Return spring 94 bellows 96 Pressure equalization valve 98 cavity 100 arrows 102 Cold storage room 104 gear carriers 106 Radial shaft seal 108 Sleeve AF support surface ASF outside F Phase G Basic area M1 outer circumferential surface M2 inner circumferential surface SF front surface 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 2022 113 216 A1

[0002]

Claims

[1] Braking device (14) for a motor vehicle, comprising a housing device (62, 74), comprising a friction disc (20) which is arranged axially between a first counter-running disc (42) and a second counter-running disc (16) of the braking device (14), wherein: - the friction disc (20) is axially displaceable relative to the housing assembly (62, 74) and relative to the counter-running discs (42, 16); - the first counter-rotating disk (42) is connected to the housing assembly (62, 74) in a rotationally fixed and axially fixed manner; - the second counter-rotating disc (16) is connected to the housing assembly (62, 74) in a rotationally fixed manner and is axially displaceable relative to the housing assembly (62, 74), relative to the friction disc (20) and relative to the first counter-rotating disc (42); - on a side (R) of the second counter-rotating disc (16) facing away from the friction disc (20) a housing cover (74) is arranged, through which at least two bolts (88) are passed, which are axially fixed to the second counter-rotating disc (16); - a nut (90) is screwed axially onto each bolt (88) on an outer surface (AS) of the housing cover (74); and - a return spring (82) is arranged on the respective nut (90). [2] Braking device (14) according to claim 1, characterized by, that on the side (R) of the second counter-rotating disc (16) facing away axially from the friction disc (20) a cooling chamber (102) through which a coolant can flow is arranged between the housing cover (74) and the second counter-rotating disc (16), wherein the respective bolt (88) is designed to be hollow inside and thereby has a respective cavity (98) which is fluidically connected to the cooling chamber (102). [3] Braking device (14) according to claim 1 or 2, characterized by , that the respective return spring (92) is designed as a disc spring. [4] Braking device (14) according to one of the preceding claims, characterized by , that the respective return spring (92) is in contact with the respective nut (92) on the one hand and with the housing cover (74) on the other hand, both in the actuated state and in the unactuated state of the brake device (14).

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