Braking system for a motor vehicle having an electric drive

Abstract

The invention relates in general to a braking system, in particular for a motor vehicle having an electric drive, and to a motor vehicle having a braking system of this kind. The braking system can comprise at least one front-wheel brake (22) and a further rear-wheel brake (25), as well as at least one brake-control device (20). At least one front-wheel brake and / or a rear-wheel brake can be in the form of a wheel brake that can be actuated solely regeneratively and has no frictional function.

Description

[0001] Braking system for an electric motor vehicle

[0002] Description

[0003] The invention generally relates to a braking system, in particular for a motor vehicle with electric drive, and to a motor vehicle with such a braking system.

[0004] "Brake-by-wire" braking systems are becoming increasingly widespread in automotive technology. These are braking systems that can operate partially or entirely without operating fluids, such as brake fluid.

[0005] With regard to the wheel brakes, it may be provided that individual wheel brakes are designed as electromechanical (dry) brakes. In this way, for example, the wheels assigned to the front axle of a motor vehicle can be equipped in a conventional manner with known hydraulic brake components as front wheel brakes, and the rear wheel brakes can be designed as electromechanical brakes. The respective hydraulic or electromechanical wheel brake can be designed as a disc brake or as a

[0006] Drum brake, whereby a friction lining can be pressed against a friction partner for braking.

[0007] A braking system, also referred to as a hybrid braking system, is described, for example, in the applicant's document DE 10 2009 041 449 A1.

[0008] Even though braking systems with electromechanical wheel brakes offer many advantages, such as the elimination of hydraulic components that are complex to install and operate, such wheel brakes are also complex and therefore cost-intensive systems.

[0009] The complexity of electromechanical wheel brakes can lead to a higher weight of these components and thus also to a higher overall weight of the motor vehicle, which can be a disadvantage, especially with regard to electrically powered vehicles with heavy batteries.

[0010] The use of friction brakes in general can also lead to dust pollution from the friction partners.

[0011] In addition, the friction partners in friction brakes are subject to a certain amount of wear during operation, which can lead to corresponding follow-up costs.

[0012] Braking systems that reduce these disadvantages or, ideally, do not have them are therefore desirable.

[0013] The inventors have taken on this task.

[0014] This problem is solved surprisingly simply by a braking system, in particular for a motor vehicle with at least four wheels, and a motor vehicle with a corresponding braking system according to one of the independent claims. Preferred embodiments and further developments of the invention can be found in the respective subclaims.

[0015] The invention therefore relates, in a first aspect, to a braking system, in particular for a motor vehicle with preferably at least four wheels, wherein at least two wheels are assigned to a first axle and two further wheels are assigned to a further, second axle, comprising at least one front wheel brake which is assigned to the first axle, at least one rear wheel brake which is assigned to the second axle, wherein the at least one front wheel brake is designed to brake at least one of the wheels of the first axle, wherein the at least one rear wheel brake is designed to brake at least one of the wheels of the second axle, at least one brake control unit, wherein the brake control unit is designed to control the at least one front wheel brake and / or the at least one rear wheel brake, and wherein at least one front wheel brake and / or at least one rear wheel brake is designed as a wheel brake that can be actuated solely regeneratively, in particular without a friction function.

[0016] For the purposes of the invention, a motor vehicle means a vehicle with axles, wherein at least one of these axles can comprise at least one, preferably at least two, steerable wheels, and furthermore, the drive of the wheels of at least one axle can be adjusted to suit the specific wheel. The motor vehicle advantageously has an electric drive.

[0017] A wheel brake that can be operated solely regeneratively is to be understood as a recuperation brake with the functionality of energy recovery, i.e. in particular as an electric motor in generator mode, and not as an eddy current brake.

[0018] In a two-axle motor vehicle, the first axle can be the front axle, and the second axle the rear axle. Accordingly, a wheel brake assigned to the first axle can also be referred to as a front wheel brake, and a wheel brake assigned to the second axle can be referred to as a rear wheel brake. However, the present invention is also generally suitable for motor vehicles with more than two axles. The present invention is also generally suitable for motor vehicles with two or more axles, whereby an axle may also have only one wheel.

[0019] The front wheel brake can therefore be designed to brake at least one of the wheels of the first axle, preferably both or all of the wheels of the first axle. Accordingly, the rear wheel brake can be designed to brake at least one of the wheels of the second axle, preferably both or all of the wheels of the second axle. The braking system according to the invention can further comprise at least one brake control unit, wherein the brake control unit can be designed to control the at least one front wheel brake and / or the at least one rear wheel brake.

[0020] According to the invention, at least one front wheel brake and / or at least one rear wheel brake can be designed as a wheel brake that can be actuated solely regeneratively and without a friction function. This means that, in particular, no friction partners for exerting friction braking can be provided for the wheel brake that can be actuated solely regeneratively, but rather the desired braking torque of the wheels of this axle is generated solely by recuperation. A wheel brake that can be actuated solely regeneratively on a wheel or on an axle is to be understood, within the meaning of the invention, that no other wheel brakes are provided on this wheel or on this axle. In other words, a wheel brake that can be actuated solely regeneratively means the presence of only a single wheel brake on the wheel or on the axle, which is accordingly designed only for recuperation.

[0021] Regenerative braking or recuperation means that by means of an electric machine or electric motor that can be used for recuperation, as can be the case, for example, in motor vehicles with an electric drive, the kinetic energy of the motor vehicle can be converted into electrical energy when the electric machine is operating as a generator. The converted electrical energy can then be fed into an electrical energy storage device, typically a vehicle battery or a capacitor. This conversion of the motor vehicle's kinetic energy into electrical energy is also referred to as (electrical) recuperation. For recuperation, a recuperation torque is typically set on the electric machine, which counteracts the movement of the motor vehicle and decelerates or brakes it.

[0022] Recuperation via the electric drive can be used, for example, to decelerate the vehicle when a brake pedal is applied. Also known as brake recuperation, braking involves adjusting a recuperation torque or power when a vehicle brake is applied, for example, when a brake pedal is applied, depending on the brake pedal travel or brake pedal force applied by the driver.

[0023] The invention is based on the underlying concept that, for braking a motor vehicle, in particular a motor vehicle with an electric drive, friction brakes do not need to be provided on all existing axles, in particular not on more than one axle. In other words, only the wheel brakes of one axle can include friction brakes, while the wheel brakes of at least one other axle of this motor vehicle do not include friction brakes and generate the braking torque solely through recuperation.

[0024] This results in several advantages of the invention.

[0025] In this way, the complexity of the braking system as a whole can be reduced, which makes the braking system according to the invention easier to manufacture and assemble.

[0026] Furthermore, the overall weight of the vehicle can also be reduced, since ideally an electric drive motor can be used as a generator for regenerative operation and thus hardly any additional components are required to fulfill the braking function.

[0027] This also makes the braking system according to the invention more cost-effective.

[0028] Furthermore, a contribution can be made to dust prevention because the friction function can be omitted on at least one axle. For the sake of clarity, the following explanations refer to two-axle motor vehicles, but this should not be understood as limiting the invention. According to a preferred embodiment of the invention, the wheel brake assigned to the wheels of the first axle, i.e., the front wheel brake, can be designed as a friction brake. In this embodiment, the wheel brake assigned to the wheels of the second axle, i.e., the rear wheel brake, can be designed as a wheel brake that can be actuated solely regeneratively and without a friction function.

[0029] According to another, likewise preferred embodiment of the invention, the wheel brake assigned to the wheels of the second axle, i.e., the rear wheel brake, can be designed as a friction brake. In this embodiment, the wheel brake assigned to the wheels of the first axle, i.e., the front wheel brake, can be designed as a wheel brake that can be actuated solely regeneratively and without a friction function.

[0030] In both of the above-mentioned embodiments of a braking system for motor vehicles, friction brakes can therefore be completely dispensed with on at least the wheels assigned to one axle of the motor vehicle.

[0031] According to one embodiment of the invention, the wheel brake, designed as a friction brake, can be dimensioned accordingly to be able to generate the entire required braking torque if necessary. This may be necessary, for example, if the capacity of the vehicle's internal energy storage system is exhausted, for example, because the batteries are fully charged.

[0032] However, the additional effort that may result from the design of this friction brake can be compensated for by the fact that no friction brake needs to be provided for the other axle.

[0033] According to one embodiment of the invention, the friction brake can be designed as a hydraulically actuated wheel brake. Designs as a hydraulically actuated disc brake or as a hydraulically actuated drum brake are possible. According to another embodiment of the invention, the friction brake can also be designed as an electromechanically actuated wheel brake. Designs as an electromechanically actuated disc brake or as an electromechanically actuated drum brake are possible.

[0034] In principle, other designs of friction brakes are also possible, so that the above list should not be understood as exhaustive.

[0035] According to one embodiment of the invention, the wheel brake that can be actuated solely by regeneration can be designed as an axle brake. In the context of the invention, a design as an axle brake can mean that all wheels on this axle can be braked with just a single wheel brake. Such a design is characterized by a very low complexity of the braking system in terms of the required components and its installation in the motor vehicle.

[0036] Another embodiment of the invention may provide for the regeneratively actuated wheel brake to be designed for each wheel individually. This means that a regeneratively actuated wheel brake can be provided on each wheel of the corresponding axle.

[0037] According to a preferred embodiment of the invention, the wheel brake, which can be actuated solely by regeneration, can be integrated into an electric drive unit or combined with an electric drive unit. Electric drives for motor vehicles with integrated regenerative braking functions are generally known and are very well suited to the invention. As explained above, the electric drive unit can be very easily switched to generator operation in order to achieve recuperation. In contrast to known systems, however, the invention makes it possible to dispense with the additional friction brake on the respective wheel. The wheel brake, which can be actuated solely by regeneration, and the electric drive unit can therefore be designed for the individual driving and / or individual braking of the wheels of an axle.According to a preferred embodiment of the invention, it can also be provided to provide only one wheel brake that can be actuated regeneratively and only one electric drive unit for the corresponding axle. This combined drive / brake unit can be positioned centrally between the wheels of the axle, although this is not mandatory. Drive and braking torque can be transmitted to the individual wheels of the axle via corresponding drive shafts. This represents a particularly simple design of the braking system according to the invention. According to another, equally preferred embodiment of the invention, the combined drive / brake unit can also be designed for each individual wheel.

[0038] The at least one brake control unit can be designed to control the at least one front wheel brake andZor the at least one rear wheel brake, wherein the control of hydraulically actuated wheel brakes can be carried out via hydraulic lines and the control of electromechanically actuated wheel brakes andZor the wheel brake that can be actuated solely regeneratively can be carried out via signal or data lines.

[0039] The electric drive unit is preferably a dual-rotor radial flux electric motor. Such electric motors have a high torque density and can provide both a high drive torque and a high braking torque. Due to the higher potential recuperation braking torque, they are therefore particularly well suited for braking systems that only include regenerative brakes on one axle. A dual-rotor radial flux electric motor is an electric motor in which a stator winding section is arranged radially between two rotor sections that comprise permanent magnets or electromagnets. The magnetic flux between the rotor and stator is then maximum in the radial direction between the adjacent rotor-stator-rotor arrangement. In one embodiment, an electric drive unit is a dual-rotor radial flux axle motor, with no friction brake or eddy-current brake integrated into this axle or the connected wheels.

[0040] In a preferred embodiment, the braking system comprises an electric drive unit in each of two wheels of an axle. These drive units are wheel-integrated dual-rotor radial flux electric motors without integrated friction brakes or eddy-current brakes. Such wheel-integrated dual-rotor radial flux electric motors exhibit, among other things, geometric reasons (higher center distance, where the drive force is effectively applied to two rotor sections), even compared to other wheel-integrated electric motors, an exceptionally high torque density and can provide both high drive torque and high braking torque.

[0041] Preferably, a regeneratively actuated wheel brake is integrated into a wheel-integrated electric motor in each of two wheels on an axle, with an inverter also being integrated into each wheel with a wheel-integrated electric motor. The inverter preferably converts direct current from the batteries into alternating current for the electric motor, and vice versa during recuperation. This allows for smaller power supply cables from the body to the wheel-integrated electric motor.

[0042] Particularly preferred are the wheel-integrated drive units designed as gearless direct drives. This reduces friction losses and makes the braking system less maintenance-intensive and more cost-effective. Wheel-integrated dual-rotor radial flux electric motors, in particular, can be designed as gearless direct drives due to their high torque density, even among wheel-integrated motors.

[0043] The brake control unit can be connected to a brake pedal via an additional signal or data line to detect the driver's braking request. In a known manner, a corresponding pedal sensor system, for example, with force and / or odometers, can be provided to detect driver actuation.

[0044] According to a preferred embodiment of the invention, the at least one brake control unit can be connected to a first power supply, and the electric drive unit can be connected to a separate second power supply. "Separate" can mean that two structurally and electrically separate power supplies or voltage sources are present, from which separate electrical lines are each led to the brake control units. If the wheel brake, which can only be actuated regeneratively, is combined with or integrated into this electric drive unit, this embodiment of the power supply also enables operation of at least one wheel brake if one power supply should fail. This provides redundancy in the braking functions.

[0045] According to a further, likewise preferred embodiment of the invention, a further, second brake control unit can be provided, which can be signal-connected to the first brake control unit via a data line. This second brake control unit can preferably have at least the essential braking functions of the first brake control unit required for safety reasons in order to provide appropriate redundancy. The second brake control unit can therefore have at least the basic functions for controlling the at least one front-wheel brake and the at least one rear-wheel brake.

[0046] According to yet another, likewise preferred embodiment of the invention, it can also be provided to connect the first and / or second brake control unit to a central control unit via a data line. This central control unit can also comprise braking functions and / or generate braking requests and transmit them to the brake control units. In this way, functions for autonomous driving can also be integrated. In a further aspect of the invention, a motor vehicle comprising a braking system as described above is also encompassed by the invention.

[0047] Further details of the invention emerge from the description of the illustrated embodiments and the appended claims.

[0048] The drawings show:

[0049] Fig. 1 shows an exemplary architecture of a braking system according to the invention with a hydraulically actuated friction brake on the front wheels and a wheel brake on the rear axle that can be actuated solely by regeneration,

[0050] Fig. 2 shows a further exemplary architecture of a braking system according to the invention with a hydraulically actuated friction brake on the front wheels and a wheel brake that can be actuated solely regeneratively on the wheels of the rear axle, and

[0051] Fig. 3 shows yet another exemplary architecture of a braking system according to the invention with an electromechanically actuated wheel brake on the front wheels.

[0052] In the following detailed description of preferred embodiments, for the sake of clarity, like reference numerals designate substantially similar parts in or on these embodiments. However, to better illustrate the invention, the preferred embodiments illustrated in the figures are not always drawn to scale.

[0053] Fig. 1 shows an exemplary architecture of a braking system 1 according to the invention with a hydraulically actuated friction brake on the front axle 11 and a wheel brake on the rear axle 12 that can be actuated solely regeneratively. For reasons of clarity, only the elements of the braking system 1 relevant to the design of the approach according to the invention are shown.

[0054] The braking system 1 can be used in particular for a motor vehicle 10. Fig. 1 shows an example of such a motor vehicle 10 with four wheels 13, 14, 15, 16, wherein two wheels 13, 14 are assigned to a first axle 11 and two further wheels 15, 16 are assigned to a further, second axle 12. However, a suitable motor vehicle can also have more than two axles 11, 12. It is also possible for only one wheel 13, 14, 15, 16 to be provided on an axle 11, 12.

[0055] The braking system 1 according to the exemplary embodiment shown in Fig. 1 comprises a front wheel brake 22 which is assigned to the first axle 11, a rear wheel brake 25 which is assigned to the second axle 12, wherein the at least one front wheel brake 22 is designed to brake at least one of the wheels 13, 14 of the first axle 11, wherein the at least one rear wheel brake 25 is designed to brake at least one of the wheels 15, 16 of the second axle 12, at least one brake control unit 20, wherein the brake control unit 20 is designed to control the at least one front wheel brake 22 and / or the at least one rear wheel brake 25, and wherein at least one front wheel brake 22 and / or at least one rear wheel brake 25 is designed as a wheel brake 26 which can be actuated solely regeneratively and without a friction function.

[0056] The front wheel brake 22 is designed to brake the wheels 13, 14 of the first axle 11. The rear wheel brake 25 is designed to brake the wheels 15, 16 of the second axle 12. The illustrated braking system 1 further comprises a brake control unit 20, wherein the brake control unit 20 is designed to control the at least one front wheel brake 22 and the at least one rear wheel brake 25. In the embodiment of the invention illustrated in Fig. 1, the front wheel brake 22 assigned to the wheels 13, 14 of the first axle 11 is designed as a friction brake. Accordingly, the rear wheel brake 25 assigned to the wheels 15, 16 of the second axle 12 is designed as a wheel brake 26 that can be actuated solely regeneratively and without a friction function.

[0057] In principle, a reversed arrangement of the friction brake and the solely regeneratively actuated wheel brake is also provided, with a friction brake being assigned to the wheels 15, 16 of the second axle 12 and a solely regeneratively actuated wheel brake being assigned to the wheels 13, 14 of the first axle 11.

[0058] In the case of the wheel brake 26 that can be actuated solely regeneratively, the friction function is dispensed with according to the invention; that is, in particular, no friction partners are provided for exerting friction braking. Rather, the desired braking torque of the wheels 13, 14, 15, 16 of the associated axle 11, 12 is generated solely by means of recuperation. This can affect all wheels 13, 14, 15, 16 of the corresponding axle. In the example in Fig. 1, this means that wheel brakes 26 that can be actuated solely regeneratively and without a friction function are provided for all wheels 15, 16 of the second axle 12.

[0059] As can be seen from Fig. 1, the braking system 1 is characterized by its low complexity, which also advantageously reduces the overall weight of the motor vehicle 10. In particular, no friction brakes or other non-regenerative brakes are provided on the rear axle 12.

[0060] In the embodiment shown in Fig. 1, the friction brake assigned to the front axle 11 is designed as a hydraulically actuated wheel brake 23, in this example as a hydraulically actuated disc brake. Other embodiments may also include hydraulically actuated drum brakes.

[0061] According to another embodiment of the invention, which is shown in Fig. 3 using a further exemplary embodiment, the friction brake can also be designed as an electromechanically actuated wheel brake 24. Designs as an electromechanically actuated disc brake, as shown in Fig. 3, or as an electromechanically actuated drum brake are possible.

[0062] In the braking system 1 shown in Fig. 1, the wheel brake 26, which can only be actuated regeneratively, is designed as an axle brake. This axle brake is configured to brake all wheels 15, 16 of the associated axle 12 with just a single wheel brake. This further simplifies the braking system 1. In other words, the wheels 15, 16 assigned to the second axle 12 can be braked with a single wheel brake 26, which can only be actuated regeneratively.

[0063] Another embodiment of the invention is shown in Fig. 2. Fig. 2 shows an exemplary architecture of a braking system 1 according to the invention, with a hydraulically actuated friction brake on each of the front wheels 13, 14 and a wheel brake 26 that can be actuated solely by regeneration on each of the wheels 15, 16 of the rear axle 12. In this exemplary embodiment, the wheel brake 26 that can be actuated solely by regeneration is designed for each wheel. This means that a wheel brake 26 that can be actuated solely by regeneration is provided on each wheel 15, 16 of the corresponding axle 12.

[0064] In the illustrated embodiments, the wheel brake 26, which can be actuated solely regeneratively, is integrated into an electric drive unit 30 or combined with an electric drive unit 30. This makes it possible to use known electric drives for motor vehicles with an integrated regenerative braking function for the invention.

[0065] Fig. 1 shows a preferred embodiment of the invention, wherein only one regeneratively actuated wheel brake 26 and only one electric drive unit 30 are provided for axle 12. This combined drive / brake unit is positioned centrally between the wheels 15, 16 of axle 12, although this is not mandatory. Drive and braking torque can be transmitted to the individual wheels 15, 16 of axle 12 via corresponding drive shafts 31.

[0066] This represents a particularly simple design of the braking system 1.

[0067] According to another, likewise preferred embodiment of the invention, such a combined drive / brake unit is designed for each wheel individually, i.e. is assigned to a wheel 15, 16 of the axle 12, as shown in Fig. 2.

[0068] However, within the meaning of the invention, such an integration or combination of electric drive unit 30 and solely regeneratively actuated wheel brake 26 is not mandatory. Rather, other arrangements and configurations are also possible, for example, an arrangement with an axle drive unit configured to drive the wheels of an axle 11, 12 and wheel-specific, solely regeneratively actuated wheel brakes 26 on the wheels 13, 14, 15, 16 of this axle 11, 12. A reverse arrangement is also possible.

[0069] In the example of Fig. 1, the brake control unit 20 is configured to actuate the hydraulically actuated wheel brakes 23 via hydraulic lines 21. Corresponding signal or data lines 72 are provided to actuate the wheel brake 26, which can only be actuated regeneratively. In this exemplary embodiment, the brake control unit 20 is configured to convert signals from a brake pedal 17, which relate to the detection of the driver's braking request, into corresponding brake signals and to transmit them hydraulically and / or electrically to the respective wheel brakes in a known manner.

[0070] Corresponding algorithms and functions for determining the braking signals can be stored in the brake control unit 20. However, as shown in the examples in Figs. 1 and 2, signal or data lines 71 can also be provided between the brake control unit 20 and a vehicle computer or a central control unit 28. The central control unit 28 is also connected directly to the wheel brake 26, which can only be actuated regeneratively, via data lines 71, so that the wheel brake 26, which can only be actuated regeneratively, can also receive braking signals from the central control unit 28. The brake control unit 20 is connected via a signal or data line to a brake pedal 17 for detecting the driver's braking request.

[0071] If the friction brake is designed as an electromechanical wheel brake 24, as shown in the exemplary embodiment in Fig. 3, no hydraulic lines are required. The brake control unit 20 is advantageously connected to the individual wheel brakes via at least two signal or data lines 71, 72 for control, thus providing redundancy. At least one signal or data line 71, 72 can also be provided by a vehicle bus.

[0072] To detect the driver's braking request, a corresponding pedal sensor system 18 can also be provided, which can, for example, comprise force and / or distance sensors for detecting an actuation by a driver.

[0073] In the braking system 1 shown in Fig. 3, the brake control unit 20 is at least partially redundant. This can be achieved, for example, by having at least the minimum functions duplicated within the brake control unit 20, for example, by two separate circuit boards. In the example from Fig. 3, the redundancy in the at least safety-critical braking functions is implemented by a second brake control unit 27. A corresponding signal or data connection is provided between the two brake control units 20, 27. Furthermore, both brake control units 20, 27 are connected to the pedal sensor system 18 via signaling.

[0074] The second brake control unit 27 comprises at least the essential braking functions required for safety reasons. The second brake control unit 27 thus has the basic functions for controlling the at least one front-wheel brake and the at least one rear-wheel brake, independent of the first brake control unit 20. To further increase reliability, the first brake control unit 20 is connected to a first power supply 50, and the second brake control unit 27 is connected to a separate second power supply 51.

[0075] In the case of electromechanical wheel brakes 24 on an axle 11, as shown in Fig. 3, it is advantageous to install the electromechanical wheel brakes 24 on this axle

[0076] 11 and the regeneratively operated wheel brakes 26 on the other axle

[0077] 12 to different voltage supplies 50, 51. Accordingly, the electromechanical wheel brakes 24 are supplied with a first voltage source 50, and the wheel brakes 26, which can only be actuated regeneratively, are supplied with a second, separate voltage source 51.

[0078] In a further development of the invention, it is provided that the at least one electromechanical wheel brake 24 is connected not only to a power supply 50, 51, but to two separate power sources 50, 51. This further increases operational capability, since if one of the power supplies 50, 51 fails, at least one wheel brake remains operational.

[0079] The invention also relates to a motor vehicle 10 which has a braking system 1 as described above.

[0080]

[0081] I Braking system

[0082] 10 motor vehicle

[0083] II Axis

[0084] 12 Axis

[0085] 13 Wheel, front left

[0086] 14 Wheel, front right

[0087] 15 Wheel, rear left

[0088] 16 Wheel, rear right

[0089] 17 Brake pedal

[0090] 18 Pedal sensors

[0091] 20 Brake control unit

[0092] 21 Hydraulic line

[0093] 22 Front brake

[0094] 23 hydraulic wheel brake

[0095] 24 electromechanical wheel brake

[0096] 25 Rear brake

[0097] 26 regenerative wheel brake

[0098] 27 Brake control unit

[0099] 28 Central control unit

[0100] 30 drive unit

[0101] 31 Drive shaft 0 Power supply 1 Power supply Data line

[0102] data line

Claims

1 . Braking system (1), in particular for a motor vehicle (10) with at least four wheels (13, 14, 15, 16), wherein at least two wheels (13, 14) are assigned to a first axle (11) and two further wheels (15, 16) are assigned to a further, second axle (12), comprising at least one front wheel brake (22) which is assigned to the first axle (11), at least one rear wheel brake (25) which is assigned to the second axle (12), wherein the at least one front wheel brake (22) is designed to brake at least one of the wheels (13, 14) of the first axle (11), wherein the at least one rear wheel brake (25) is designed to brake at least one of the wheels (15, 16) of the second axle (12), at least one brake control unit (20, 27, 28), wherein the brake control unit (20, 27, 28) is designed to control the at least one front wheel brake (22) and / or the at least one rear wheel brake (25),and wherein at least one front wheel brake (22) and / or at least one rear wheel brake (25) is designed as a solely regeneratively actuated wheel brake (26) without a friction function., 2. Braking system (1) according to the preceding claim, characterized in that the at least one front wheel brake (22) is designed as a friction brake, wherein preferably the at least two wheels (13, 14) of the first axle (11) each comprise a friction brake.

3. Braking system (1) according to one of the preceding claims, characterized in that the at least one rear wheel brake (25) is designed as a friction brake, wherein preferably the at least two wheels (15, 16) of the second axle (12) each comprise a friction brake.

4. Brake system (1) according to one of the preceding claims, characterized in that the friction brake is designed as a hydraulically actuated wheel brake (23), preferably as a disc brake or as a drum brake.

5. Brake system (1) according to one of the preceding claims, characterized in that the friction brake is designed as an electromechanically actuated wheel brake (24), preferably as a disc brake or as a drum brake.

6. Braking system (1) according to one of the preceding claims, characterized in that the wheel brake (26) which can be actuated regeneratively alone is designed as an axle brake and is set up to brake the wheels (13, 14, 15, 16) of one of the axles (11, 12) during operation, and wherein the wheels (13, 14, 15, 16) of this axle (11, 12) preferably do not comprise any further wheel brakes, in particular no friction brakes.

7. Braking system (1) according to one of the preceding claims, characterized in that the wheel brake (26) which can be actuated solely regeneratively is designed for each wheel and is assigned to the wheels (13, 14, 15, 16) of one of the axles (11, 12), and wherein the wheels (13, 14, 15, 16) of this axle (11, 12) preferably do not comprise any further wheel brakes, in particular no friction brakes.

8. Braking system (1) according to one of the preceding claims, characterized in that the wheel brake (26) which can be actuated solely regeneratively is integrated into an electric drive unit (30) or is combined with an electric drive unit (30).

9. Braking system (1) according to one of the preceding claims, characterized in that the solely regeneratively actuated wheel brake (26) and the electric drive unit (30) are designed for wheel-individual driving and / or wheel-individual braking of the wheels (13, 14, 15, 16) of an axle (11, 12), and wherein the wheels (13, 14, 15, 16) of this axle (11, 12) preferably do not comprise any further wheel brakes, in particular no friction brakes.

10. Braking system (1) according to one of claims 8 or 9, characterized in that the electric drive unit (30) is a double-rotor radial flux electric motor.

11. Braking system (1) according to claim 10, characterized in that an electric drive unit (30) is a double-rotor radial flux axle motor, wherein neither a friction brake nor an eddy current brake is integrated into this axle (11, 12) nor into the connected wheels (13, 14, 15, 16).

12. Braking system (1) according to claim 10 or 11, comprising an electric drive unit (30) in each of two wheels (13, 14, 15, 16) of an axle (11, 12), which are wheel-integrated double-rotor radial flux electric motors without a wheel-associated friction brake or wheel-associated eddy current brake.

13. Braking system (1) according to one of claims 7 to 12, characterized in that a regeneratively actuated wheel brake (26) in each of two wheels (13, 14, 15, 16) of an axle is integrated into a wheel-integrated electric motor, wherein an inverter is also integrated into each wheel (13, 14, 15, 16) with a wheel-integrated electric motor.

14. Braking system (1) according to one of claims 7 to 13, characterized in that the wheel-integrated drive units (30) are designed as a gearless direct drive.

15. Brake system (1) according to one of the preceding claims, characterized in that the at least one brake control unit (20) is connected to a first voltage supply (50) and the drive unit (30) is connected to a second voltage supply (51) separate therefrom.

16. Brake system (1) according to one of the preceding claims, characterized in that a further, second brake control unit (27) is provided, which is connected to the brake control unit (20) via at least one data line, and wherein the second brake control unit (27) at least the safety-relevant Braking functions of the brake control unit (20).

17. Brake system (1) according to one of the preceding claims, characterized in that the first and / or the second brake control unit (20, 27) is connected via a data line to a Central control unit (28).

18. Motor vehicle (10) comprising a braking system (1) according to one of the preceding claims.

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