Electric wheel hub drive system, and motor vehicle

Abstract

The invention relates to an electric wheel hub drive system (5) for a motor vehicle, comprising a wheel brake (9) of the friction type which is integrated in the wheel hub drive system (5) and comprises a wheel brake rotor (11) and a wheel brake stator (10). The wheel brake rotor (11) is configured such that it is cooled passively without fluid ducts. For system decoupling and improved, simplified brake cooling, it is defined according to the invention that at least one contactless coolant is provided which allows the wheel brake rotor (11) to incouple accumulated brake waste heat for the purpose of cooling into a stator component (6, 10) which is preferably fluid-cooled.

Description

[0001] Electric wheel hub drive system and motor vehicle

[0002] The invention relates to a novel integrated friction brake comprising a wheel brake rotor for cooperation with at least one friction lining and a wheel brake stator, for an electric wheel hub drive comprising drive rotor and fluid-cooled drive stator which is arranged essentially centrally in the interior of a vehicle wheel.

[0003] DE 10 2010 008 230 A1 relates to a drive wheel with a wheel hub motor and a brake that are cooled with a cooling fluid. The cooling fluid used to cool the wheel hub motor is routed through at least part of the brake. For this purpose, appropriately branched coolant channels can be defined for shared thermal management.

[0004] DE 10 2021 121 502 A1 includes a wheel hub drive together with a braking device and a combined, fluid-circuited cooling circuit such that a first line section is designed to dissipate heat from the drive stator and a second line section is provided which is designed to control the temperature of the braking device.

[0005] The branched circulation solution proposed in the known state of the art appears to be complex and is perceived as not very flexible to implement, which is also related to the complex fluidic branched strand routing + circulation cooling including sealed channel design.

[0006] Accordingly, it is an object of the present invention to improve the availability and robustness of a generic wheel brake as efficiently as possible and with the highest functional safety.

[0007] The object of the invention is achieved by an electric wheel hub drive system according to claim 1 and a motor vehicle according to claim 17. Preferred embodiments can be found in the subclaims. According to the invention, at least one contactless coolant is provided, which allows the wheel brake rotor to couple accumulated brake waste heat into a preferably fluid-cooled stator component for cooling purposes. This preferably eliminates the need for direct fluid cooling of the wheel brake, and contactless, in particular passive, coolants are used to dissipate the majority of the brake heat and prevent overheating of the heat-sensitive components of the wheel hub drive system.However, active fluid cooling of the motor components of the wheel hub drive system is not excluded and can interact with the contactless coolants to provide a sufficiently large cooling effect even in the event of emergency braking or a long braking process.

[0008] The term stator component can refer to the drive motor stator or the wheel brake stator.

[0009] The wheel brake, namely a drive-integrated brake, should continue to be designed to be as easy to install and maintain as possible, yet still be decoupled. The mutual functional compatibility and assembly-friendly integration required in highly compacted installation spaces should be further improved. Mutual negative influences due to mechanical, thermal, or other disturbances should be minimized as much as possible to avoid negative repercussions or performance losses. At the same time, a highly compact and durable wheel drive system should be presented that can be easily implemented in a vehicle manufacturing process using a division of labor.

[0010] The present invention circumvents the problems of direct fluidic wheel brake rotor cooling by offering a competitively improved solution using passively adapted wheel brake rotor cooling. For example, the invention enables an efficiently improved and fluid- and contact-free defined brake heat extraction between the rotatable wheel brake rotor and the rotationally fixed and fluid-cooled drive motor stator. Other or additional extraction methods are proposed. The present invention therefore offers a novel solution to overheating problems of friction brakes allocated close to the drive. The description of the invention is primarily based on the example of drum brake integration.

[0011] The invention defines a contactless and fluid-free thermal connection / connector / coupling for dissipating brake heat from the wheel brake rotor by means of a contactless, i.e., indirect, connection to the coolant or heat sink, i.e., connection to a heat sink. This indirect connection can, but does not have to, refer solely to the use of a liquid cooling system of the fluid-cooled wheel hub drive, but can also include other heat-exchanging means or media, such as, in particular, direct or indirect air cooling with an (electrically driven) fan, or passively parasitically as a result of vehicle movement and passing ambient air.

[0012] As a result, the invention enables the friction energy of an encapsulated wheel brake, which is converted into heat during friction braking, to be indirectly decoupled and transported away via a heat sink, cooling fluid, etc., which is released to the ambient air, for example, via a heat exchanger downstream in the fluid circulation, or is made available for other subsystems for energetic conversion or utilization (brake heat pump for the purpose of thermal-electrical energy conversion, heating of a passenger compartment at low temperatures or temperature control of an electrical power storage device).

[0013] Since a conventional wheel hub drive housing / stator is usually stationary and permanently installed on the vehicle, whereas a wheel brake rotor, such as the brake drum, rotates, a non-contact connector can be used to integrate and utilize a convection (physical heat conduction) and heat radiation transfer path in thermal management. In one embodiment, a non-contact coolant is at least one rib, preferably at least two ribs. The ribs are preferably arranged concentrically around a central wheel rotation axis. One or more of the ribs can have a cooling effect and / or a sealing function with respect to the wheel brake, in particular a brake drum. The sealing function serves both to reduce / prevent the escape of brake dust from the wheel brake in general (especially the problem of particulate matter) and to protect the engine components in particular.Depending on the design, one or more ribs can have a greater or lesser cooling effect. Likewise, depending on the design, one or more of the ribs can primarily serve a sealing function. Multiple ribs can form a labyrinth seal between the wheel brake and the drive motor stator (especially between the brake drum and a stator end plate), which particularly effectively keeps brake dust in the wheel brake.

[0014] In one embodiment, the cooling elements comprise interlocking fins. This allows for excellent sealing through a long labyrinth seal. At the same time, heat transfer through the fins can be increased, particularly through larger emission and absorption surfaces for thermal radiation.

[0015] Preferably, at least two ribs extend from the drive motor stator, in particular from a stator end plate extending substantially radially, to the brake drum. This embodiment can also improve both the sealing effect against brake dust and the heat transfer from the brake drum to the stator end plate.

[0016] The term "stator end plate extending essentially in the radial direction" is to be understood in this document to mean that the stator end plate has an extension in the radial direction that is at least twice as large as in the axial direction (parallel to the wheel rotation axis). The axial extension of the stator end plate in the axial direction is to be understood without the ribs described later. Preferably, at least one rib extends from the brake drum to the drive motor stator, in particular to a stator end plate extending essentially in the radial direction. This increases both the sealing effect against brake dust and the heat transfer from the brake drum to the stator end plate.

[0017] It is preferred if at least one rib extending from the drive motor stator (in particular a stator end plate) interacts with one or more steps in a radial outer wall of the brake drum. This can increase the sealing effect against brake dust and the heat transfer from the brake drum to the stator end plate.

[0018] In one embodiment, the cooling means comprise at least one heat-conducting plate that extends at least partially from the drive motor stator, in particular from a stator end plate extending substantially in the radial direction, to the brake drum. The heat-conducting plate can be provided alternatively or in addition to ribs and / or a heat shield.

[0019] It is preferred if the cooling means comprise at least one heat shield, which is arranged radially between the brake drum and a drive motor rotor of the wheel hub drive system and is configured to at least partially absorb heat radiation from the brake drum generated as a result of a braking operation. The heat shield preferably extends circumferentially around and parallel to a central wheel rotation axis. The heat shield preferably extends concentrically around the brake drum. The heat shield preferably extends over more than 75% of the axial length of the brake drum.

[0020] The heat shield is preferably designed as one of several ribs extending from the drive motor stator, in particular from a stator end plate extending substantially radially, substantially parallel to a central wheel rotation axis. The rib heat shield can interact with another rib, which primarily has a sealing effect. In one embodiment, the wheel hub drive system is designed as a dual-rotor radial flux motor with a drive motor rotor and a drive motor stator, wherein a winding section of the drive motor stator is arranged radially between an outer drive motor rotor and an inner drive motor rotor. A dual-rotor radial flux motor has a particularly high torque density and, even for an electric motor, particularly high efficiency.

[0021] Particularly preferably, the wheel hub drive system is designed as a direct drive without a wheel-integrated transmission.

[0022] Preferably, a heat shield is arranged in the radial direction between the brake drum and the internal drive motor rotor, wherein permanent magnets are arranged on a radial outer side of the internal drive motor rotor.

[0023] According to the invention, a motor vehicle is further provided comprising at least two wheel hub drive systems according to one of the preceding embodiments.

[0024] Further details of the invention emerge from the description of the illustrated embodiments and the appended claims.

[0025] The drawings show:

[0026] Fig. 1 is an isometric partial sectional view of an embodiment of a wheel hub drive system according to the invention,

[0027] Fig. 2 is a schematic sectional view of an embodiment of a wheel hub drive system according to the invention,

[0028] Fig. 3 is a schematic sectional view of an embodiment of a wheel hub drive system according to the invention, Fig. 4 is a sectional view of an embodiment of a wheel hub drive system according to the invention,

[0029] Fig. 5 is a sectional view of an embodiment of a wheel hub drive system according to the invention,

[0030] Fig. 6 is a sectional view of an embodiment of a wheel hub drive system according to the invention, and

[0031] Fig. 7 is a sectional view of an embodiment of a wheel hub drive system according to the invention.

[0032] In the following detailed description of preferred embodiments, like reference numerals designate substantially the same or identical 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.

[0033] As shown schematically in the figures, a significant enlargement of the surface and visible areas "A" between the stationary and rotating components is recommended to increase the transferred heat flow "P".

[0034] A further structural design includes the following: A motor vehicle wheel 1 with tire 2 and rim 3 is rotatably mounted on a wheel hub 4 in conjunction with an electric wheel hub drive 5 RNA and can be electrically driven or braked regeneratively. The wheel hub drive 5 has a drive motor stator 6 and a drive motor rotor 7, as well as one or more electrical connections 8. The motor vehicle wheel 1, which is arranged so that it can be electrically driven and also electrically braked regeneratively via the wheel hub drive 5, is further assigned a friction-type wheel brake 9 for the purpose of transmitting service braking requests. The friction wheel brake 9 comprises at least one wheel brake stator 10 mounted in a rotationally fixed manner, a wheel brake rotor 11 mounted rotatably with the vehicle wheel 1 via the wheel hub 4 and at least one friction lining 12 arranged in a rotationally fixed manner and brake-actuated by means of actuators 13. The friction lining 12 is therefore available as required (iedifferentiated according to the actuation case for the presentation of an electronically controlled service brake request or electronically controlled parking brake request) in friction cooperation with the wheel brake rotor 11 .

[0035] The electric service brake system of each vehicle wheel 1, which is essentially integrated from several partial braking systems or modules, is electrically controlled by at least one electronic control unit (ECU) depending on the driver's wishes or automatically. Microprocessor-controlled and / or automatic wheel brake control is possible. Each vehicle wheel 1 can be assigned an individual wheel brake control unit (WCU) for this purpose. An electric wheel brake control unit (WCU) may fully or partially integrate the electronics of an electric wheel hub drive control. The wheel brake 9 can also partially integrate an electric parking brake (EPB) fully or at least in important parts (e.g., an MGU = Motor-Gear-Unit) (combined electric wheel brake 9). An electronic brake control unit (ECU), such as in particular a wheel brake control unit (WCU), can integrate software, hardware, etc. for the electronic control of an electric parking brake (EPB).It is understood that any control input within the framework of a service brake control is implemented in a needs-based, efficient, and economical manner through mutual adjustment, synchronization, and integration between the recuperative partial braking system of the wheel hub drive 5 and the friction brake 9. The wheel brake 9, and in particular its actuators, can be equipped with sensors S, namely, in particular, with an electrical brake load measuring device S, for the purpose of needs-based control.

[0036] When integrating the wheel brake 9 into the center of the wheel hub drive 5, there is a need for efficient brake waste heat management due to cooling requirements. According to the invention, this is primarily achieved by contactless, i.e., passively cooled, waste heat management. Nevertheless, it is not precluded that brake waste heat from wheel brake components can be passively coupled, for example, into the peripheral cooling systems of other systems or components without contact. For example, it is possible for brake waste heat from the friction brake to be passively dissipated into (cooled) components of a wheel hub drive without contact, and the respective component of the wheel hub drive can, of course, also be fluidly cooled (wheel hub drive with a fluid cooling system). Transfer means can be provided for the passive, contactless coupling of the heat.Suitable transfer means include, by way of example but by no means exclusively or conclusively, a heat-conducting plate, a brake anchor plate, a special rib-like or comb-like structure (any combination of the above features is expressly possible) so that brake waste heat from the friction brake 9 can be dissipated passively and at least partially into other or peripheral components or cooling systems. With particularly contactless and cooling fins or comb-like thermal coupling that alternately overlap or interlock with one another, based on the transfer structure between the drive motor stator 6 of the wheel hub drive 5 and the rotating wheel brake rotor / brake drum 11, improved heat transfer is achieved. The drive motor stator 6 or the housing-side fins can be specially supplied with coolant by means of additional fluid channels inserted on the stator side, thus providing an increased cooling effect (reduction of "Tenv"), i.e.Heat transfer is further improved. Furthermore, the efficiency or heat transfer coefficient ("alpha") can be further improved by the targeted application of a flow-turbulence-enhancing element, for example, on a comb / fin surface or in the cooling / flow chamber. Furthermore, it may be useful to increase the emission coefficient ("epsilon"), for example, by applying a thin, technical coating / surface finish to the comb / coupling surface.

[0037] Through brake waste heat and brake cooling measures further developed according to the invention, it is possible to further compress the installation spaces involved without the components adversely affecting one another. This makes it possible to encapsulate the friction brake with high performance and braking availability, which also has a positive effect on particulate matter retention properties. Consequently, the realization of almost closed wheel arches or wheel rims is advisable in order to, for example, efficiently reduce vehicle air resistance, i.e. the vehicle's drive energy requirement. It is possible to use the friction heat energy inevitably generated during friction braking in another form, for example by converting it in an environmentally friendly way using a heat pump. For this purpose, a heated coolant is also available for further use in other systems.Furthermore, the invention is not only suitable for motor vehicles but also for industrial brakes, elevators in buildings, or combined electric brake drives (e.g. robotics and / or automation technology).

[0038] Figures 1 to 7 show embodiments of the wheel hub drive system 5 according to the invention with integrated drum brake with different contactless coolants.

[0039] Figures 1 and 2 show embodiments in which a heat-conducting plate 10A extends partially from a radially extending stator end plate 6A to the brake drum 11. The heat-conducting plate 10A interacts with several steps in a radial outer wall of the brake drum 11 to achieve both a heat-dissipating and a sealing effect against the escape of brake dust. Part of the braking heat can thus be conducted into the stator end plate 6A near the wheel bearing.

[0040] In Figures 3 to 7, two (Figures 4 to 7) or three (Figure 3) ribs 22, 23 are provided, each extending from the stator end plate 6A to the brake drum 11. The rib 23 in Figure 7 also serves as a heat shield. The ribs 22, 23 extending from the stator end plate 6A are preferably formed integrally with the stator end plate 6A, which enables particularly good heat transfer.

[0041] In the embodiments of Figs. 3, 5, and 6, the cooling elements comprise interlocking fins 22, 24. This allows for an excellent sealing effect through a long labyrinth seal. At the same time, heat transfer through the fins 22, 24 can be increased, particularly through larger emission and absorption surfaces for thermal radiation.

[0042] Figs. 3, 5, and 6 show that one (Fig. 6), two (Fig. 5), or three (Fig. 3) ribs 24 extend from the brake drum 11 to the stator end plate 6A. The rib(s) 24 from the brake drum 11 interact with the ribs 22 extending from the stator end plate 6A. In particular, they form an effective labyrinth seal and heat transfer structure.

[0043] Alternatively, one or more ribs 22 extending from the stator end plate 6A may also interact with one or more steps in a radial outer wall of the brake drum 11, as can be seen from Figures 4 and 7. This also allows a labyrinth seal and a passive cooling effect on the brake drum to be achieved.

[0044] Furthermore, a heat shield 23, 25 can be provided as a contactless coolant (see Figs. 4 to 7). The heat shield 23, 25 is arranged radially between the brake drum 11 and the drive motor rotor 7 of the wheel hub drive system 5. Preferably, the heat shield 23, 25 extends over more than 75% of the axial length of the brake drum 11.

[0045] The wheel hub drive system 5 shown in Figs. 1 to 7 is designed as a dual-rotor radial flux motor with a drive motor rotor 7 and a drive motor stator 6. A winding section 27 of the drive motor stator 6 is arranged radially between an outer drive motor rotor 26 and an inner drive motor rotor 28. Permanent magnets 29 are arranged on a radial outer side of the inner drive motor rotor 28 (see Figs. 3 and 4). Permanent magnets 29 are arranged on a radial inner side of the outer drive motor rotor 26. The wheel hub drive system 5 can also include a wheel-integrated converter 30 for converting vehicle-side direct current into wheel hub drive system-side alternating current and vice versa (see Figs. 3, 4).

[0046] The converter 30 may be arranged in a converter housing partially formed by the stator end plate 6A or adjoining it.

[0047] List of reference symbols

[0048] 1 motor vehicle wheel

[0049] 2 tires

[0050] 3 rim

[0051] 4 Wheel hub

[0052] 5 Wheel hub drive / wheel hub drive system

[0053] 6 Drive motor stator

[0054] 6A stator end plate

[0055] 7 Drive motor rotor

[0056] 8 Electrical connection of the RNA (wheel hub drive)

[0057] 9 Wheel brake / friction brake

[0058] 10 Wheel brake stator

[0059] 10A heat conducting plate

[0060] 11 Wheel brake rotor

[0061] 12 Friction lining

[0062] 13 Brake actuator

[0063] 14 MMI - Brake - Human-Machine - Interface for Brake

[0064] 15 MMI - RNA - Human-Machine-Interface for Wheel Hub Drive

[0065] 16 heat exchangers

[0066] 17 Coolant circulation line / ring line

[0067] 18 Coolant circulation line / ring line

[0068] 20 Coolant interface

[0069] 21 Coolant interface

[0070] 22 rib

[0071] 23 Rib / Heat Shield

[0072] 24 ribs

[0073] 25 Heat shield

[0074] 26 Outdrive motor rotor

[0075] 27 winding section

[0076] 28 Internal drive motor rotor

[0077] 29 permanent magnets

[0078] 30 Inverter Ax axial direction = wheel rotation axis

[0079] R Radial direction

[0080] S Sensor - especially brake load measuring device

Claims

Patent claims 1. Electric wheel hub drive system (5) for a motor vehicle, comprising a friction-type wheel brake (9) integrated into the wheel hub drive system (5), comprising a wheel brake rotor (11) and a wheel brake stator (10), wherein the wheel brake rotor (11) is designed to be passively cooled without fluid channels, characterized in that at least one contactless coolant is provided which allows the wheel brake rotor (11) to couple accumulated brake waste heat into a preferably fluidically cooled stator component (6, 10) for the purpose of cooling.

2. Wheel hub drive system (5) according to claim 1, comprising a drive motor rotor (7) which can be coupled radially outwards R with respect to a central wheel rotation axis (Ax) and in a rotationally fixed manner to the motor vehicle wheel (1), which drive motor rotor encloses the wheel brake (9) in a capsule-like manner, and a drive motor stator (6) which can be placed in a rotationally fixed and fluid-cooled manner on a vehicle axle component, such as in particular on a pivot bearing, wherein the wheel brake (9) has the wheel brake rotor (11) in cooperation with a friction lining (12) which is mounted in a rotationally fixed and brake-actuable manner with the wheel brake stator (10), which friction lining cooperates with at least one brake actuator (13), such as in particular with a spreading device.

3. Wheel hub drive system (5) according to one or more of the preceding claims, characterized in that the brake actuator (13) is designed electrically and in particular electromechanically, and has an associated electrical wheel brake control unit (WCU).

4. Wheel hub drive system (5) according to one or more of the preceding claims, characterized in that the wheel brake (9) is designed as a drum brake system with a brake drum as a wheel brake rotor (11).

5. Wheel hub drive system (5) according to one or more of the preceding claims, characterized in that the wheel brake (9) comprises an integrated electric parking brake EPB.

6. Wheel hub drive system (5) according to one or more of the preceding claims, characterized in that a preferably electric brake actuator (13) enables brake load detection for the purpose of electronic friction brake control, such as in particular having an electric brake load measuring device S.

7. Wheel hub drive system (5) according to one of the preceding claims, characterized in that a contactless coolant is at least one rib (22, 23, 24), preferably at least two ribs (22, 23, 24).

8. Wheel hub drive system (5) according to claim 7, characterized in that the non-contact cooling means comprise interlocking ribs (22, 24).

9. Wheel hub drive system (5) according to claim 7 or 8, characterized in that at least two ribs (22, 23) extend from the drive motor stator (6), in particular from a stator end plate (6A) extending in the radial direction, to the brake drum (11).

10. Wheel hub drive system (5) according to claims 7 to 9, characterized in that at least one rib (23) extends from the brake drum (11) to the drive motor stator (6), in particular to a stator end plate (6A) extending in the radial direction.

11. Wheel hub drive system (5) according to claims 7 to 10, characterized in that at least one rib (22, 23) extending from the drive motor stator (6) cooperates with one or more steps in a radial outer wall of the brake drum (11).

12. Wheel hub drive system (5) according to one of the preceding claims, characterized in that the contactless coolants comprise at least one heat conducting plate (10A) which extends at least partially from the drive motor stator (6), in particular from a stator end plate (6A) extending in the radial direction, to the brake drum (11).

13. Wheel hub drive system (5) according to one of the preceding claims, characterized in that the contactless cooling means comprise at least one heat shield (23, 25) which is arranged in the radial direction between the brake drum (11) and a drive motor rotor (7) of the wheel hub drive system (5) and is designed to at least partially intercept heat radiation from the brake drum (11) generated as a result of a braking operation.

14. Wheel hub drive system (5) according to claim 13, characterized in that the heat shield (23) is designed as one of a plurality of ribs (23) extending from the drive motor stator (6), in particular from a stator end plate (6A) extending in the radial direction, substantially parallel to a central wheel rotation axis (Ax).

15. Wheel hub drive system (5) according to one of the preceding claims, characterized in that the wheel hub drive system (5) is designed as a double-rotor radial flux motor with a drive motor rotor (7) and a drive motor stator (6), wherein a winding section (27) of the drive motor stator (6) is arranged in the radial direction between an outer drive motor rotor (26) and an inner drive motor rotor (28).

16. Wheel hub drive system (5) according to claim 15, characterized in that a heat shield (23, 25) is arranged in the radial direction between the brake drum (11) and the internal drive motor rotor (28), wherein permanent magnets (29) are arranged on a radial outer side of the internal drive motor rotor (28).

17. Motor vehicle comprising at least two wheel hub drive systems (5) according to one of the preceding claims.

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