WO2024114851A1

WO2024114851A1 - Braking system

Info

Publication number: WO2024114851A1
Application number: PCT/DE2023/100833
Authority: WO
Inventors: Benedikt Grubauer; Simon Ortmann
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2022-11-28
Filing date: 2023-11-08
Publication date: 2024-06-06
Also published as: DE102022131332A1

Abstract

The invention relates to a braking system (1) of a motor vehicle (3) that can be electrically driven by an electric machine (2), wherein the braking system (1) comprises a disc brake (4) with a brake disc (5) and brake jaws (7) that can be frictionally connected to the brake disc (5) on their end faces (6), and the electric machine (2) has a rotor (8) that is torque-transmittingly coupled to at least one vehicle wheel (9) of the motor vehicle (3), wherein the disc brake (4) is accommodated in a brake housing (9) and the brake disc (5) of the disc brake (4) is torque-transmittingly connected to the rotor (8) of the electric machine (2), wherein the brake disc (5) has a hydraulic brake disc cooling system (10), in which a casing surface (11) of the brake disc (5) can be applied with a brake disc cooling fluid (12), which can be introduced through a fluid inlet (13) in the brake housing (9) and can be discharged from same through a fluid outlet (14) in the brake housing (9).

Description

Braking system

The present invention relates to a braking system of a motor vehicle that can be driven electrically by means of an electric machine, wherein the braking system comprises a disc brake with a brake disc and brake shoes that can be brought into frictional engagement with the brake disc on their end faces, and the electric machine has a rotor that is coupled to at least one vehicle wheel of the motor vehicle in a torque-transmitting manner.

Electric motors are increasingly being used to drive motor vehicles in order to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to be able to offer users the usual driving comfort. A detailed description of an electric drive can be found, for example, in an article in the magazine ATZ 113th year, 05/2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrated and flexible electric drive unit for electric vehicles. This article describes a drive unit for an axle of a vehicle, which includes an electric motor that is arranged coaxially to a bevel gear differential.

Such motor vehicles with a hybridized or electrified drive train can not only accelerate and brake with the help of an electric machine, but also. During braking, the electric machine is operated as a generator and the recuperated energy is used, for example, to charge the battery. For safety reasons, however, an additional mechanical braking device is still required. With drives close to the wheels, such as a wheel hub motor or an electric axle, this results in a more difficult installation space situation.

Especially in vehicles with an electric wheel hub drive, a so-called E-Wheel Drive, brakes with discs are often used to slow down the vehicle. However, there are also brakes in the design as Disc brakes with floating calipers, disc brakes with fixed calipers, drum brakes and multi-disc brakes are known.

For example, DE 10 2019 120 409 A1 discloses a braking device for a wheel hub drive arrangement in which the brake partners that are fixed relative to the circumferential direction have cooling channels. The axially movable brake partner is actuated via brake cylinders. The brake partner that is movable in the circumferential direction is designed as a disk carrier.

It is the object of the invention to provide a braking system which is improved in terms of its cooling for a motor vehicle which is electrically driven by means of an electric machine.

This object is achieved by a braking system of a motor vehicle that can be electrically driven by means of an electric machine, wherein the braking system comprises a disc brake with a brake disc and brake shoes that can be brought into frictional engagement with the brake disc on their end faces, and the electric machine has a rotor that is coupled to at least one vehicle wheel of the motor vehicle in a torque-transmitting manner, wherein the disc brake is accommodated in a brake housing and the brake disc of the disc brake is connected to the rotor of the electric machine in a torque-transmitting manner, wherein the brake disc has a hydraulic brake disc cooling system in which a jacket surface of the brake disc can be acted upon by a brake disc cooling fluid that can be introduced through a fluid inlet of the brake housing and discharged from the latter via a fluid outlet of the brake housing.

This provides the advantage that a type of complementary brake is coupled to the electric machine, which can exert a braking effect on a vehicle wheel. In order to be able to apply the high braking torques to brake the vehicle without a thermally induced drop in braking performance, the braking system also has a liquid-based brake disc cooling system. The preferred arrangement in direct proximity to the electric drive motor also makes it possible to avoid the heat energy recovered from the braking process by the liquid-based brake disc cooling, which is generated close to the potential heat consumers, and thus to avoid loss-related heat transport over longer distances through the vehicle.

First, the individual elements of the claimed subject matter of the invention will now be explained in the order in which they appear in the set of claims, and particularly preferred embodiments of the subject matter of the invention will be described below.

The braking system according to the invention has the function of braking a shaft to be braked, for example by means of a frictional connection.

The brake system according to the invention is arranged in a brake housing for this purpose. The brake housing encloses the brake system. A brake housing can also accommodate one or more brake actuators. The brake housing can also be part of a cooling system and designed in such a way that cooling fluid is supplied to the brake system via the brake housing and/or the heat can be dissipated to the outside via the housing surfaces. In addition, the brake housing protects the brake system from external mechanical and/or chemical influences. A brake housing can in particular be made from a metallic material. The brake housing can advantageously be formed from a metallic cast material, such as gray cast iron or cast steel. In principle, it is also conceivable to form the brake housing entirely or partially from a plastic. It is also possible for the brake housing to be made in one piece or in several parts. The brake housing can also be designed entirely or partially as part of a motor housing of an electrical machine or a transmission housing of a transmission coupled to the electrical machine. The brake housing and the motor housing or the transmission housing preferably form a structural unit. For this purpose, the brake housing can be screwed to the engine housing or the gearbox housing, for example. The brake housing is arranged in a rotationally fixed manner relative to the disc brake. The brake housing is preferably designed in such a way that abrasion that occurs during braking cannot escape from the brake housing. This can prevent unwanted pollution of the environment with brake abrasion. Furthermore, encapsulating the brake system in this way can also reduce braking noise in the environment. Another advantageous aspect of this encapsulation is that the braking performance of the brake system is independent of the weather conditions outside the motor vehicle.

The brake system according to the invention comprises a disc brake. The brake disc is the rotating part of a disc brake, on whose front surfaces the brake shoes act in a releasable manner in order to decelerate the rotational movement of the brake disc by means of frictional engagement during operation of the disc brake. The brake disc preferably has a brake disc body.

Brake discs can preferably be formed from a metal casting, such as in particular gray cast iron, spheroidal cast iron or cast steel, and then machined preferably by turning and/or milling. It is also possible to use silicon carbide reinforced with carbon fibers and/or a carbon fiber-reinforced ceramic material in order to achieve a particularly low weight of a brake disc. It is also conceivable, in particular for a particularly cost-effective provision of a brake disc, to punch it out of a sheet metal.

A brake disc preferably has a hollow cylindrical spatial shape, the axial extent of which is significantly smaller than its diameter. The brake disc can be designed in one piece or in multiple pieces. In a multiple-piece brake disc, the individual brake disc elements can preferably be arranged in layers in the axial direction, resulting in a type of sandwich construction.

The brake disc body is the part of the brake disc on which the brake shoes act with friction to reduce the rotational speed of the brake disc. The brake disc body can have a plurality of Brake disc cooling channels, by means of which in particular heat and/or brake abrasion can be dissipated from the brake disc body.

The braking system can also have a shaft connection. The shaft connection of the brake disc connects the brake disc body to the rotating shaft to be braked, which is also referred to as the brake shaft. The shaft connection can be designed as a separate component that is arranged in the torque flow between the brake disc body and the shaft to be braked, or as a connection between the brake disc body and the shaft to be braked. It is possible for the shaft to be braked and the shaft connection to be formed in one piece, in particular monolithically. In principle, it is also conceivable for the shaft connection and the brake disc body to be formed in one piece. It can also be preferred for the shaft to be braked, the shaft connection and the brake disc body to be formed in one piece, in particular monolithically. The shaft connection can also be made, for example, by means of a positive connection, a frictional connection and/or a material connection between the shaft to be braked and the brake disc body. For example, the shaft connection can be made by means of a press fit, a spline or by welding.

The brake system according to the invention has a hydraulic brake disc cooling system. A hydraulic brake disc cooling system uses a brake disc cooling fluid to cool the brake disc. The brake disc cooling fluid can act on the brake disc at least in sections and/or be guided through the brake disc. The hydraulic brake disc cooling system is preferably designed in such a way that the brake disc cooling fluid cannot reach the friction surfaces between the brake shoes and the brake disc body.

For this purpose, the hydraulic brake disc cooling system can have at least one, but preferably a plurality of brake disc cooling channels in which the brake disc cooling fluid is guided. It is further preferred that the hydraulic brake disc cooling system is connected to a brake disc cooling circuit, within which the frictional heat absorbed by the brake disc cooling fluid is dissipated from the disc brake and fed to a heat sink, such as a heat exchanger.

In order to create a frictional connection between the brake shoes and the brake disc, the brake shoes, in particular with their brake shoe friction linings, are pressed preferably axially against the brake disc by means of a brake actuator.

A brake system can also have a brake actuator. A brake actuator has the function of actuating the brake, i.e. putting it into a frictionally engaged operating state and an operating state released from the frictional engagement. The brake actuator can be actuated pneumatically, hydraulically, by electric motor, mechanically, electromagnetically or any combination thereof. The brake actuator can preferably have at least one linearly displaceable piston, which can preferably be displaced in the axial direction. A brake actuator preferably comprises two linearly displaceable pistons, and it is also preferred that the pistons can be displaced in a direction directed towards one another.

The braking system according to the invention is intended for a motor vehicle that can be driven electrically by means of an electric machine. Electric machines in the sense of this application serve to convert electrical energy into mechanical energy and/or vice versa, and generally comprise a stationary part referred to as a stator, stand or armature and a part referred to as a rotor or runner and arranged to be movable relative to the stationary part. In connection with this invention, an electric machine can be designed in particular as a rotary machine. In such rotary electric machines, a distinction is made in particular between radial flux machines and axial flux machines. A radial flux machine is characterized in that the magnetic field lines in the air gap formed between the rotor and stator extend in the radial direction, while in the case of a Axial flux machine, the magnetic field lines extend in the axial direction in the air gap formed between the rotor and stator. In connection with the present invention, an electric machine is provided in particular for use within a drive train of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km/h, preferably greater than 80 km/h and in particular greater than 100 km/h can be achieved. The electric machine particularly preferably has an output greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is further preferred that the electric machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, most particularly preferably greater than 12,500 rpm.

The electric machine can have a housing, which is also referred to as a motor housing. The motor housing encloses the electric machine. A motor housing can also accommodate the control and power electronics, and preferably also at least parts of the braking system. The motor housing can also be part of a cooling system for the electric machine and can be designed in such a way that cooling fluid is supplied to the electric machine via the motor housing and/or the heat can be dissipated to the outside via the motor housing surfaces. In addition, the motor housing protects the electric machine and any electronics present from external mechanical and/or chemical influences. A motor housing of the electric machine can in particular be made of a metallic material. The motor housing can advantageously be formed from a metallic cast material, such as gray cast iron or cast steel. In principle, it is also conceivable to form the motor housing entirely or partially from a plastic. It is also possible for the motor housing of the electric machine to be made in one piece or in several parts.

A rotor is the rotating part of an electrical machine. The rotor comprises in particular a rotor shaft and one or more rotor bodies formed from rotor laminations arranged on the rotor shaft in a rotationally fixed manner. The rotor shaft can be hollow, which on the one hand saves weight and on the other hand and which also allows the supply of lubricant or coolant to the rotor body. The rotor shaft can be coupled in particular to the brake shaft of the braking system.

The electric machine can preferably be coupled to a transmission which is designed to generate a drive torque for the motor vehicle. The drive torque is particularly preferably a main drive torque, so that the motor vehicle is driven exclusively by the drive torque.

In particular, it can be provided that the electric machine and the transmission are arranged in a common drive train housing. Alternatively, it would of course also be possible for the electric machine to have a motor housing and the transmission to have a transmission housing, in which case the structural unit can then be effected by fixing the transmission arrangement relative to the electric machine. This structural unit is sometimes also referred to as an e-axle. The drive train housing is preferably made of a metallic material, particularly preferably aluminum, gray cast iron or cast steel, in particular by means of a primary forming process such as casting or die casting. In principle, however, it would also be possible to form the drive train housing from a plastic. The drive train housing can particularly preferably have a pot-like basic shape, so that the electric machine and the transmission can be inserted into the drive train housing via the open front side of the drive train housing.

The electric machine preferably has a motor housing and/or the gearbox a gearbox housing, whereby the structural unit can then be achieved by fixing the gearbox to the electric machine. The gearbox housing is a housing for accommodating a gearbox. Its task is to guide existing shafts via the bearings and to give the wheels (possibly cam disks) the degrees of freedom they require under all loads without hindering them in their rotation and possible orbital movement, as well as to absorb bearing forces and support moments. A gearbox housing can be single- or multi-shell, i.e. undivided or divided. The gear housing should in particular also be able to dampen noise and vibrations and also safely absorb hydraulic fluid. The gear housing is preferably made of a metallic material, particularly preferably aluminum, gray cast iron or cast steel, in particular by means of a primary forming process such as casting or die casting.

The transmission can further preferably be configured as a planetary transmission or comprise a planetary transmission. The planetary transmission can preferably have a sun gear and a plurality of planetary gears that mesh with the sun gear and are rotatably mounted in a planetary gear carrier, which move in rotation around the sun gear, as well as a ring gear arranged coaxially to the sun gear, in which the planetary gears roll.

The transmission can also have a differential gear. A differential gear is a planetary gear with one input and two outputs. Its function is usually to drive two wheels of a motor vehicle so that they can turn at different speeds in curves but with the same propulsive force.

In order to implement different drive or operating modes for the motor vehicle, one or more separating clutches can be provided within the torque path between the electric machine and a vehicle wheel. A separating clutch can, for example, be arranged between the output of the electric machine and the input of the transmission, so that the electric machine can be decoupled from the transmission, thereby enabling the motor vehicle to coast. It would also be conceivable to arrange a separating clutch between the output of the transmission and a vehicle wheel or wheels, thereby also enabling the motor vehicle to coast. Finally, it is also possible to arrange a separating clutch between the input of the braking system and the output of the electric machine, whereby the braking system can be completely decoupled from the electric machine.

For the purposes of this application, motor vehicles are considered to be land vehicles that are moved by mechanical power without being tied to railway tracks. Motor vehicle can, for example, be selected from the group of passenger cars (PCs), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (COMs) or tractors.

Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically meaningful manner and can define further embodiments of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, with further preferred embodiments of the invention being presented.

According to an advantageous embodiment of the invention, it can be provided that the lateral surface of the brake disc has a circumferential lateral surface section with a plurality of fluid guide elements which protrude radially from the lateral surface and/or radially into the lateral surface.

The advantage of this design is that the cooling performance can be optimized using appropriate fluid guidance. The fluid guidance elements can, for example, be designed as webs extending in the axial direction. Blade-like designs of the fluid guidance elements are also conceivable in principle. The fluid guidance elements can also have brake disk cooling channels through which the brake disk cooling fluid can flow.

The brake disc cooling channels can in particular run radially through a brake disc, so that a spoke-like configuration of the brake disc cooling channels is formed in the brake disc. The brake disc cooling fluid is preferably conveyed radially outwards through the brake disc cooling channels by centrifugal force. The brake disc cooling channels can have any contour in cross-section. However, for manufacturing reasons, circular contours and rectangular contours are generally preferred.

According to a further preferred development of the invention, it can also be provided that the brake disc has a first radially has a circumferential ring element that projects outwards and engages with play in a corresponding first groove in the brake housing and/or the brake disc has a second circumferential ring element that projects radially outwards from the jacket surface and engages with play in a corresponding second groove in the brake housing.

This makes it possible to provide a contactless sealing element which separates or seals a “wet space” which can be acted upon by the brake disc cooling fluid from the friction surfaces of the brake shoes with the brake disc body.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the first ring element and the second ring element are arranged on a first axial side at a distance from the jacket surface section having the plurality of fluid guide elements, so that an optimized separation between the "wet space" and the friction surfaces of the disc brake can be realized.

According to another particularly preferred embodiment of the invention, it can be provided that the brake disc has a third circumferential ring element protruding radially outward from the jacket surface, which engages with play in a corresponding third groove of the brake housing and/or the brake disc has a fourth circumferential ring element protruding radially outward from the jacket surface, which engages with play in a corresponding fourth groove of the brake housing.

This makes it possible to achieve the effect of a further optimized “wet space friction surface” separation.

Furthermore, the invention can also be further developed in such a way that the third ring element and the fourth ring element are arranged on a second axial side at a distance from the lateral surface section having the plurality of fluid guide elements, which also contributes to further improved separation between the “wet space” and the friction surfaces on both end faces of the brake disc body. In a likewise preferred embodiment variant of the invention, it can also be provided that the fluid inlet is arranged in the direction of gravity in the bottom region of the brake housing and/or the fluid outlet is arranged in the direction of gravity in the head region of the brake housing.

This makes it possible, on the one hand, to enable a gravity-induced outflow of brake disc cooling fluid from the “wet space” or from the brake housing and/or, on the other hand, to enable a centrifugal force-induced escape of the brake disc cooling fluid when the brake disc rotates in the head area of the brake housing.

It may also be advantageous to further develop the invention in such a way that the fluid inlet and the fluid outlet are connected to a brake disc cooling circuit, via which the brake disc cooling fluid that can be heated in the brake system can be fed to a heat exchanger, so that optimal cooling of the disc brake and/or further use of the friction-related waste heat of the disc brake can take place.

According to a further preferred embodiment of the subject matter of the invention, it can be provided that the brake disc is arranged in a rotationally fixed manner on a rotatably mounted brake shaft, which is coupled to a rotor shaft of the rotor in a torque-transmitting manner. This can achieve, among other things, that the mechanical braking effect of the brake system can be supported by the generator operation of the electric machine. It is also conceivable for the electric machine to drive the brake system in frictional engagement as a motor, so that the frictional heat generated in this way can be dissipated via the brake disc cooling fluid and, for example, fed to another use via a heat exchanger, for example for heating the passenger compartment of the vehicle.

Finally, the invention can also be advantageously designed such that a first actuatable brake cylinder and a second actuatable brake cylinder are accommodated in the brake housing, wherein the first brake cylinder engages a first of the brake shoes and the second brake cylinder engages a second of the brake shoes in frictional engagement with one of the end faces of the brake disc or releases the frictional connection with one of the front surfaces of the brake disc. This has the advantage that the usual brake calliper of a disc brake can be dispensed with, or - in other words - the brake housing takes over the function of the brake calliper.

It may also be preferred that the first ring element and the second ring element are designed to be substantially identical. It is highly preferred that the first ring element and/or the second ring element are designed to be monolithic with the brake disc.

It is also preferred that the third ring element and the fourth ring element are designed to be substantially identical, wherein it is again particularly preferred that the third ring element and/or the fourth ring element are designed to be monolithic with the brake disc.

In this context, it is also advantageous that the first ring element and the second ring element with the corresponding first groove and second groove form a first labyrinth seal. The third ring element and the fourth ring element with the corresponding third groove and fourth groove can also preferably form a second labyrinth seal.

In this case, it is also particularly preferred that the first labyrinth seal and the second labyrinth seal are arranged axially spaced apart and define an annular space through which the brake disc cooling fluid can flow. This annular space thus forms a wet space within the brake housing, which separates the brake disc cooling fluid from the frictional contacts between the brake disc body and the brake shoes. In this case, the circumferential jacket surface section with a plurality of fluid guide elements is preferably axially enclosed by the first labyrinth seal and the second labyrinth seal. The fluid inlet and the fluid outlet of the brake housing preferably open into the annular space.

In a further preferred embodiment of the brake system, the brake shaft is connected to the brake housing by means of a arranged rolling bearing arrangement. The brake shaft is most preferably sealed against the brake housing by means of a brake shaft seal

The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

It shows:

Figure 1 shows an electrically driven motor vehicle with a braking system in a schematic block diagram,

Figure 2 shows a braking system of a motor vehicle coupled to an electric machine in a schematic axial sectional view,

Figure 3 shows a braking system with a disc brake in an axial sectional view,

Figure 4 is a detailed view of the head area of the braking system known from Figure 3 in an axial section,

Figure 5 is a detailed view of the base area of the braking system known from Figure 3 in an axial section.

Figure 1 shows a braking system 1 of a motor vehicle 3 that can be electrically driven by means of an electric machine 2.

The braking system 1 comprises a disk brake 4 with a brake disk 5 and brake shoes 7 which can be brought into frictional engagement with the brake disk 5 at their end faces 6, which can be clearly seen in Figure 2. The electric machine 2 accommodated in the motor housing 52 has a rotor 8 which is coupled to at least one vehicle wheel 51 of the motor vehicle 3 in a torque-transmitting manner. In the embodiment of Figure 2, the torque path A transmission 54 is arranged between the electric machine and the vehicle wheel 51, which can be decoupled from the torque path via the separating clutch 53, so that, for example, a sailing operation of the motor vehicle 3 can be realized.

The electric machine 2, the transmission 54 and the disc brake 4 form a structural unit, which is also referred to as the axle drive train 55.

The disc brake 4 is accommodated in a brake housing 9 and the brake disc 5 of the disc brake 4 is connected to the rotor 8 of the electric machine 2 in a torque-transmitting manner. It can be clearly seen from Figure 2 that actuating the disc brake 4 thus generates a braking torque in the torque path from the electric machine 2 to the vehicle wheel 51, as a result of which the latter can be braked. The braking torque is thus generated via the brake disc 5, on the front of which two brake shoes 7 can act in such a way that the axial force counteracts. The axial force is generated via two hydraulically connected hydraulic brake cylinders 26, 27, each of which represents a brake actuator. The hydraulic brake cylinders 26, 27 are pressurized with a hydraulic fluid via the brake fluid channel 42.

The brake disc 5 is arranged in a rotationally fixed manner on a rotatably mounted brake shaft 24, which, as mentioned, is coupled to a rotor shaft 25 of the rotor 8 in a torque-transmitting manner. The brake shaft 24 is rotatably mounted relative to the brake housing 9 by means of a roller bearing arrangement 38 arranged in the brake housing 9 and is sealed relative to the brake housing 9 by means of a brake shaft seal 39. Speed and torque can be introduced into the disc brake 4 from a corresponding spline of the rotor shaft 25 via a spline 43 incorporated in the brake shaft 24. The brake shaft 24 is guided via the roller bearing arrangement 38. On the side of the brake shaft 24, on which the spline 43 is arranged for introducing speed and torque, the brake system 1 is sealed relative to the environment by means of the radially acting Brake shaft seal 39 sealed.

A first actuatable brake cylinder 26 and a second actuatable brake cylinder 27 are accommodated in the brake housing 9, with the first brake cylinder 26 bringing a first of the brake shoes 7 and the second brake cylinder 27 bringing a second of the brake shoes 7 into frictional engagement with one of the end faces 6 of the brake disc 5 or releasing the frictional engagement with one of the end faces 6 of the brake disc 5. To generate the braking torque, two opposing brake shoe friction linings 41 are each arranged on a movable brake shoe body 40 on the end faces 6. The brake shoe friction linings 41 are located in the upper area relative to the axis of the brake shaft 24. The required displacement and axial force is generated by means of two hydraulic brake cylinders 26, 27 with seals 50 with a rectangular cross section. The groove geometries in which the seals 50 with a rectangular cross section are arranged are designed in such a way that self-adjustment of wear takes place. In the non-actuated state, the movable brake shoe bodies 40 are moved into a predefined starting position by means of one or more spring elements 46 under spring force. The movable brake shoe bodies 40 are guided axially via a pin-like guide element 45, 47. An end stop 48 is also formed in this area, which limits the axial travel of the brake shoe body 40.

The brake disc 5 has a hydraulic brake disc cooling system 10, in which a jacket surface 11 of the brake disc 5 can be subjected to a brake disc cooling fluid 12, which can be introduced through a fluid inlet 13 of the brake housing 9 and can be discharged from the latter via a fluid outlet 14 of the brake housing 9. The fluid inlet 13 is arranged in the direction of gravity in the base area 20 of the brake housing 9 and the fluid outlet 14 is arranged in the direction of gravity in the head area 21 of the brake housing 9. The fluid inlet 13 and the fluid outlet 14 are connected to a brake disc cooling circuit 22, via which the brake disc cooling fluid 12 that can be heated in the brake system 1 can be fed to a heat exchanger 23. As Brake disc cooling fluid 12 Water or a mixture of water and another substance (e.g. water-glycol mixtures) is used to dissipate heat.

The outer surface 11 of the brake disc 5 has a circumferential outer surface section 30 with a plurality of fluid guide elements 15 that protrude radially from the outer surface 11 and/or radially into the outer surface 11. In the embodiment shown, the fluid guide elements 15 are designed as webs that extend in the axial direction. In contrast to brake discs with internal geometry known from the prior art, no holes are arranged in the end faces 6 of the brake disc 5, so that no brake disc cooling fluid 12 can pass axially through the brake disc 5 in the direction of the friction-loaded outer surfaces of the brake disc 5.

It is also clearly apparent from Figures 3-5 that the brake disk 5 has a first circumferential ring element 16 that protrudes radially outward from the jacket surface 11 and engages with play in a corresponding first groove 17 of the brake housing 9. The brake disk 5 also has a second circumferential ring element 18 that protrudes radially outward from the jacket surface 11 and engages with play in a corresponding second groove 19 of the brake housing 9. As shown in Figures 3-5, the first ring element 16 and the second ring element 18 are arranged on a first axial side 33 at a distance from the jacket surface section 30 that has the plurality of fluid guide elements 15.

Figures 3-5 also show that the brake disk 5 has a third circumferential ring element 28 that protrudes radially outward from the jacket surface 11 and that engages with play in a corresponding third groove 29 of the brake housing 9 and/or the brake disk 5 finally also has a fourth circumferential ring element 31 that protrudes radially outward from the jacket surface 11 and that engages with play in a corresponding fourth groove 32 of the brake housing 9. The third ring element 28 and the fourth ring element 31 are spaced apart on a second axial side 34 from the jacket surface section 30 that has the plurality of fluid guide elements 15. arranged.

The first ring element 16 and the second ring element 18 are essentially identical and designed monolithically with the brake disc 5. The same applies to the third ring element 28 and the fourth ring element 31, which are also essentially identical and designed monolithically with the brake disc 5.

The first ring element 16 and the second ring element 18 form with the corresponding first groove 17 and second groove 19 a first labyrinth seal

35 and the third ring element 28 and the fourth ring element 31 with the corresponding third groove 29 and fourth groove 32 a second labyrinth seal

36. The first labyrinth seal 35 and the second labyrinth seal 36 are arranged axially spaced apart and define an annular space 37 through which the brake disk cooling fluid 12 can flow. The annular space 37 can therefore also be referred to as a "wet space". The circumferential shell surface section 30 with a plurality of fluid guide elements 15 is axially enclosed by the first labyrinth seal 35 and the second labyrinth seal 36. The fluid inlet 13 and the fluid outlet 14 of the brake housing 9 open into the annular space 37.

The brake disc cooling fluid 12 is fed into the annular space via the distribution geometry 44

37 for fluid guidance and distribution of the brake disc 5. In order to prevent a flow of the fluid flow in the direction of the end faces 6 of the brake disc 5, two labyrinth seals 35,36 are arranged in the brake disc 5.

The collecting geometry 49 is formed at the lowest point of the brake disk 5 relative to the center of the earth. This is designed in such a way that the brake disk cooling fluid 12 is guided by gravity in the direction of the fluid inlet 13 through the inclined geometry. The ring elements 18, 31 protruding radially outward from the brake disk 5 protrude in the inclined geometry of the collecting geometry 49.

The invention is not limited to the embodiments shown in the figures. The above description is therefore not to be considered as limiting, but rather as explanatory. The following patent claims are to be understood in such a way that a named feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a ranking.

List of reference symbols

1 braking system

2 electric machine

3 Motor vehicle

4 Disc brake

5 Brake disc

6 front surfaces

7 brake shoes

8 Rotor

9 Brake housing

10 Brake disc cooling system

11 Shell surface

12 Brake disc cooling fluid

13 Fluid inlet

14 Fluid outlet

15 fluid guide elements

16 Ring element

17 grooves

18 Ring element

19 grooves

20 Floor area

21 Head area

22 Brake disc cooling circuit

23 Heat exchangers

24 Brake shaft

25 Rotor shaft

26 brake cylinders

27 brake cylinders

28 Ring element

29 Groove

30 Shell surface section

31 Ring element

32 grooves 33 Page

34 Page

35 Labyrinth seal

36 Labyrinth seal

37 Annular space

38 Rolling bearing arrangement

39 Brake shaft seal

40 Brake shoe body

41 Brake shoe friction lining

42 Brake fluid channel

43 spline

44 Distribution geometry

45 Guide pin

46 Spring element

47 Guide element

48 End stop

49 Collection geometry

50 Seal

51 Vehicle wheel

52 Engine housing

53 Separating clutch

54 Gearbox

55 Axle drive train

Claims

Claims Brake system (1) of a motor vehicle (3) which can be driven electrically by means of an electric machine (2), wherein the brake system (1) comprises a disc brake (4) with a brake disc (5) and brake shoes (7) which can be brought into frictional engagement with the brake disc (5) on their end faces (6), and the electric machine

(2) has a rotor (8) which is connected to at least one vehicle wheel (51) of the motor vehicle in a torque-transmitting manner

(3) is coupled, characterized in that the disc brake (4) is accommodated in a brake housing (9) and the brake disc (5) of the disc brake (4) is connected to the rotor (8) of the electric machine (2) in a torque-transmitting manner, the brake disc (5) having a hydraulic brake disc cooling system (10) in which a jacket surface (11) of the brake disc (5) can be acted upon by a brake disc cooling fluid (12) which can be introduced through a fluid inlet (13) of the brake housing (9) and discharged from the brake housing (9) via a fluid outlet (14). Braking system (1) according to claim 1, characterized in that the jacket surface (11) of the brake disc (5) has a circumferential jacket surface section (30) with a plurality of fluid guide elements (15) which protrude radially out of the jacket surface (11) and/or radially into the jacket surface (11). Brake system (1) according to claim 1 or 2, characterized in that the brake disc (5) has a first circumferential ring element (16) projecting radially outward from the jacket surface (11) which engages with play in a corresponding first groove (17) of the brake housing (9) and/or the brake disc (5) has a second circumferential ring element (16) projecting radially outward from the jacket surface (11) has an outwardly projecting circumferential ring element (18) which engages with play in a corresponding second groove (19) of the brake housing (9).

4. Brake system (1) according to claim 3, characterized in that the first ring element (16) and the second ring element (18) are arranged on a first axial side (33) at a distance from the jacket surface section (30) having the plurality of fluid guide elements (15).

5. Brake system (1) according to claim 3 or 4, characterized in that the brake disc (5) has a third circumferential ring element (28) protruding radially outward from the jacket surface (11) which engages with play in a corresponding third groove (29) of the brake housing (9) and/or the brake disc (5) has a fourth circumferential ring element (31) protruding radially outward from the jacket surface (11) which engages with play in a corresponding fourth groove (32) of the brake housing (9).

6. Brake system (1) according to claim 5, characterized in that the third ring element (28) and the fourth ring element (31) are arranged on a second axial side (34) at a distance from the jacket surface section (30) having the plurality of fluid guide elements (15).

7. Braking system (1) according to one of the preceding claims, characterized in that the fluid inlet (13) is arranged in the direction of gravity in the bottom region (20) of the brake housing (9) and/or the fluid outlet (14) is arranged in the direction of gravity in the head region (21) of the brake housing (9). Braking system (1) according to claim 7, characterized in that the fluid inlet (13) and the fluid outlet (14) are connected to a brake disk cooling circuit (22) via which the brake disk cooling fluid (12) that can be heated in the braking system (1) can be fed to a heat exchanger (23). Braking system (1) according to one of the preceding claims, characterized in that the brake disk (5) is arranged in a rotationally fixed manner on a rotatably mounted brake shaft (24) which is coupled to a rotor shaft (25) of the rotor (8) in a torque-transmitting manner. Braking system (1) according to one of the preceding claims, characterized in that a first actuatable brake cylinder (26) and a second actuatable brake cylinder (27) are accommodated in the brake housing (9), wherein the first brake cylinder (26) brings a first of the brake shoes (7) and the second brake cylinder (27) brings a second of the brake shoes (7) into frictional engagement with one of the end faces (6) of the brake disc (5) or releases the frictional engagement with one of the end faces (6) of the brake disc (5).