FIELD OF THE INVENTION

The present invention relates to wheel assembly for an electric vehicle according to the preamble of patent claims. BACKGROUND OF THE INVENTION

Wheel hub motors for electrical vehicles normally comprise a non-rotating part (stator) and a thereto coaxial arranged rotating part (rotor). The rotor is arranged radially outside to the stator. The rotor normally comprises several permanent mag nets (magnets). In several publications, such as EP21 49470B 1 , DE1 0201 61 03808A1 , DE20201 0002923U 1 , DE20201 41 04276U 1 , the rotor acts as a rim. Some of the publications are directed to an advantageous arrangement of the magnets in the rim. DE 1 02008036560B4 e.g. describes the clueing of the magnets to the rim or the receiving of the magnets in a special adapter ring. US201 6068055A was published on 1 0.03.201 5 on behalf of Ford Global Tech nologies LLC and discloses a drive wheel having an electric wheel hub motor for a motor vehicle that includes a stator arranged around a wheel hub and is connected to the wheel hub in a non-rotatable manner. A rotor is mounted in such a manner that it can rotate relative to the stator to drive a wheel rim connected to the rotor in a non-rotatable manner. At least two energy storage devices are arranged between the wheel hub and the stator to output electrical energy for operation of the electric wheel hub motor. The energy storage devices are embodied in each case in the shape of a ring segment in such a manner that the energy storage devices form a closed ring around the wheel hub when lying adjacent to one another.

US2004099455A was published on 27.05.2005 and discloses an in-wheel motor with a non-rotary case to which the motor stator is fixed and is connected to a knuckle which is a part around the wheel of a vehicle by a first elastic member, a rotary case to which the rotor of the motor is fixed and rotatably connected to the non-rotary case through a bearing is connected to the wheel by a second elastic member so as to float-mount the in-wheel motor to parts around the wheel.

SUMMARY OF THE INVENTION

A major disadvantage of conventional systems wheel assemblies for electric vehi- cles comprising wheel hub motors is that they have a relatively high weight and hence contribute significantly to the total weight of a vehicle which inter alia has a negative impact on energy efficiency. As well, the resulting non-suspended masses have a negative impact on the dynamic driving characteristics of electric vehicles. A main reason for the high weight are the materials used for the structural compo- nents of the wheel assemblies, such as the rim to receive a tire as well as the struc tural components of the motor. Conventional wheel assemblies are essentially made from metallic materials having a relatively high specific weight. In addition, metallic materials typically limit the potential for functional integration which re sults in inefficient arrangement of the components and non-optimal load paths. This in particular holds true for electric motors where magnetic fields need to be generated and altered in very specific ways. Furthermore, the joining technigues used in conventional wheel assemblies typically make additional means for protec tion of the brittle permanent magnets necessary. As most magnets typically are also prone to corrosion, special measures against harmful environmental influences as well as electrochemical corrosion between the different components must be taken, leading to an increase of total weight.

In order to solve at least one of the aforementioned problems, a wheel assembly for an electric vehicle comprising a wheel hub motor according to the present in vention typically comprises a stator that has a stator housing with a stator housing widened section. The stator housing widened section typically has an in general cy- lindrical shape and that extends in an axial direction. Within this context, a general cylindrical shape will typically be a shape which has a circular cross-section and an essentially constant diameter along the axial direction. A variation with such a sta tor housing widened section has a particularly high structural competence as well as it allows efficient propulsion. However, the diameter may also be variable in axial direction, hence e.g. have a conical and/or barrel-like shape. As well, the stator housing widened section may e.g. also have a rotationally symmetrical polygonal cross-section. According to the invention, the stator housing at an in axial direction proximal end merges into a stator axle that is arranged coaxially to and extending away from the stator housing and has a smaller diameter than the stator housing widened section. Within the context to the invention the proximal end is the end that is directed to the wheel assembly's attachment to the vehicle, such as the chas sis of a car or truck, or a (single) swingarm of a motorcycle. Within the context of the invention, the distal end is the end directed away from the attachment to the vehicle. In case the wheel assembly is attached on both sides to a vehicle, the prox imal end will typically be the end at which more load is transferred to an external structure. The wheel assembly further comprises a rotor comprising a rotor housing that is arranged coaxially to and rotatable around the stator. The rotor housing has a rotor housing widened section that encompasses at least a portion of the sta tor housing widened section at a certain distance. According to the present inven tion the rotor housing widened section at an in axial direction proximal end merges into a hollow-cylindrical rotor axle which has a smaller diameter than the rotor housing widened section. According to the invention the rotor is supported with respect to the stator axle by at least one bearing.

Thus, a wheel assembly for single and multi-lane vehicles can be obtained which allows a high degree of functional integration as well as a particularly advantageous arrangement of its components with respect to mass distribution and space re- guirements. In addition, a wheel assembly according to the present invention facil- itates repair and maintenance. As well, such wheel assembly allows to obtain rela tively small variations in the distance between the rotor and the stator if compared to conventional wheel assemblies and hence to increase energetic efficiency of the wheel assembly. In addition, the wheel assembly allows to reduce the number of rotary seals if compared to conventional wheel assemblies as well as the relative speed of the corresponding sealing members to each other can be reduced, allow ing more durable and reliable sealing as well as application of more economic rotary seals. In a variation of the present invention at least one electrical winding - respectively coil - is arranged at the stator housing widened section to generate a magnetic field for applying torgue on the rotor. Particularly good results may be obtained if the at least one electrical winding is arranged at least partially in a stator cage that is mechanically interconnected with the stator housing. The stator cage may be a separate member that is mechanically interconnected with the stator housing such that no relative displacement in circumferential direction are possible. Particularly good results may be obtained if the stator cage is mechanically interconnected with the stator housing widened section.

In a variation of the invention, the at least one electrical winding is arranged at least partially in a stator housing wall that is an integral part of the stator housing. Hence, the stator cage may be an integral part of the stator housing, in particular of the stator housing widened section. Thus, a particularly advantageous stress and strain distribution can be obtained in the stator and durability of the wheel assembly can be increased whereas total weight be decreased. This in particular holds true if at least a portion of the stator housing is made from a fiber-reinforced plastic, as will be explained in more detail below. A variation of a wheel assembly according to the invention that has a particularly high durability and lightweight design can be obtained if the stator housing and/or the rotor housing is/are at least partially made from a fiber reinforced plastic whereas the stator axle and/or the rotor axle is/are essentially made from a metal- lie material.

In a variation of the present invention, the stator housing widened section encom passes a cavity that constitutes a receiving space suitable to receive power electron ics to operate the magnetic field generated by the at least one electrical winding. Due to the special design and arrangement of the stator and rotor according to the invention, a large-volume receiving space can be provided. Conseguently, effective space in a vehicle can be increased as well as the need of pulsed power cables can be minimized. In addition, driving safety in case of collisions can be increased. The receiving space may be divided into several chambers, e.g. by means of one or mul tiple dividing walls. The multiple chambers may be fluidically interconnected with each other or at least some of them may be fluidically separated from each other.

In a variation of the invention the receiving space is accessible from the outside, e.g. from the distal end of the stator housing widened section. Thus, maintenance of the wheel assembly, in particularly of components arranged in the receiving space can be facilitated. A variation that has a high durability can be obtained if the receiving space is closed by a closure arrangement. Such a closure arrangement may be completely remov able from wheel assembly (as subseguently will be shown in more detail with re spect to the figures) or may also be folded away to access the receiving space. In a variation of the invention, the closure arrangement comprises a stator closure arranged at the distal end of the stator housing widened section. For some applica tions, the stator closure may be configured to close at least a portion of the receiv ing space (respectively at least one chamber if the receiving space is divided into multiple chambers as described above) hermetically against the exterior. For such a variation, at least part of the stator closure may have a plate- and/or disc-like shape. Alternatively or in addition, at least part of the stator closure may be formed like a spoked wheel/disk.

A wheel assembly that has a particularly good durability can be obtained if the clo sure arrangement comprises a rotor closure arranged at the distal end of the rotor housing widened section. Good results may be obtained if a rotor closure essentially hermetically closes the interior of wheel assembly. Thus, the interior of the wheel assembly can be encapsulated and protected against harmful environmental influ ences. Intrusion of humidity and dust into the interstitial space between the rotor housing and the stator housing as well as into a receiving space (if present) can thus efficiently be prevented. The rotor closure and/or stator closure may be re movable for repair and maintenance. A mechanically highly competent wheel assembly may be obtained if the rotor clo sure is supported with respect to the stator by at least one distal bearing. Hence tipping where the stator and rotor rub against each other can efficiently be pre vented. In a variation of the invention the at least one distal bearing is arranged at the stator closure, as will be explained in more detail below. Thus, maintenance of the wheel assembly can be simplified as well as relatively small distal bearings can be used, and conseguently total prize of the wheel assembly be decreased.

In a variation of the invention the rotor housing widened section may comprise and/or may be interconnectable with a tire reception means suitable to receive at least one tire. The tire reception means may be interconnected with the rotor, in particular the rotor axle by means of a wheel disc, which may e.g. be a spoked disc or a plate disc. Thus, a wheel with tire can easily be obtained. The tire reception means may be an integral part or may be made from multiple components.

In a variation of the invention the tire reception means may comprise at least one proximal rim edge and at least one distal rim edge suitable to receive a tire thereon.

In a variation of the invention, the rotor housing widened section comprises a cou pling means to interconnect at least one rim (wheel ring) on the outside of the rotor. In a variation of the invention the coupling means comprises a locking element to establish positive locking between the rim and the rotor housing widened section in circumferential direction of the rotor housing widened section. Good results may be obtained of the coupling means comprises at least one protrusion and/or inden tation extending in axial direction of the rotor housing widened section as will be explained in more detail below.

In a variation of the invention the rotor housing widened section comprises at least one magnet. The magnet will typically be a permanent magnet, however, alterna tively or in addition the magnet may be an electromagnet. In order to obtain highly efficient propulsion, a multiplicity of magnets may be arranged distributed in cir cumferential direction of the rotor housing widened section.

Particularly good results may be obtained if the rotor housing widened section com- prises at least one magnet and constitutes at least part of a rim (e.g. of a rim well) to receive a tire. Thus a variation of the invention with a particularly functionally integrated design can be obtained.

A wheel assembly that has a particularly highly efficient propulsion may be ob tained if the at least one magnet is at least partially embedded in a housing wall of the rotor housing widened section. Thus, brittle and corrosion-sensitive magnets can be efficiently protected against corrosive environmental influences as well as mechanical damage. Particularly good results may be obtained if the at least one magnet is at least partially embedded in a housing wall made from a fiber-rein- forced plastic. Thus, a magnet may be embedded in a particularly advantageous way. A fiber-reinforced may e.g. comprise reinforcing fibers made from carbon fi bers, glass fibers, mineral fibers, polymer fibers such as aramid fibers as well as combinations of these types of fibers. Thus, the magnetic field generated by the at least one magnet is not negatively affected by the rotator housing as well as a highly integrated design can be obtained. In addition, total weight of the rotor can be minimized and hence acceleration and deceleration of a wheel be optimized. For 5 certain applications, the at least one magnet may be coated with an electrically non-conductive layer in order to reduce electro-corrosive effects. Alternatively or in addition, electrically non-conductive layers of reinforcing fibers may be arranged adjacent to the at least one magnet, such as e.g. a layer of fiber-reinforced plastic comprising glass fibers. o In a variation of the invention the at least one magnet is arranged at a rotor cage.

Good results may be obtained if such a rotor cage is at least partially embedded in a housing wall made from a fiber-reinforced plastic which may help during produc tion of the wheel assembly by ensuring correct positioning of the at least one mag net as well as to obtain an even stress and strain distribution in the rotor. Thus, a5 particularly advantageous stress and strain distribution may be obtained and con- seguently total volume of the rotor be reduced.

In a variation of the invention the rotor housing widened section is at least partially made from fiber-reinforced composite material. Particularly good results may be obtained if the stator housing widened section may be at least partially made from0 a fiber-reinforced plastic. In a variation of the invention, the stator axle is hollow and comprises at least one electrical wire or cable. The electrical wire may e.g. may be used for power supply or control of the wheel assembly. Alternatively or in addition, also at least one cool ant line may be arranged in the stator axle such as for temperature control/regula- tion of a power electronics arranged inside of a receiving space as described herein.

For some applications the rotor axle is interconnected to a disc of a braking system. Hence, highly efficient braking of a wheel assembly can be ensured.

In a variation of the invention, the stator axle (is attached to a mount. The mount may be part of a vehicle's body/chassis or steering system. The mount may com- prise a flange. For some applications the rotor axle (21 0) is supported with respect to the mount by at least one proximal bearing. Thus, a structurally highly compe tent wheel assembly may be obtained

It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an over- view or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to pro-vide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illus trate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

The herein described invention will be more fully understood from the detailed de scription given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The draw-

5 ings are showing schematically:

Fig. 1 schematically shows a first variation of a wheel assembly according to the present invention in a perspective view from above;

Fig. 2 schematically shows the variation of a wheel assembly of Fig. 1 with part of the wheel assembly being partially clipped for illustrative purposes in0 a perspective view from above;

Fig. 3 schematically shows the variation of a wheel assembly of Fig. 1 partially disassembled and in a perspective view from above;

Fig. 4 schematically shows a portion of the variation of a wheel assembly of

Fig. 1 with part of the wheel assembly being clipped for illustrative pur5 poses in a perspective view from above;

Fig. 5 schematically shows a second variation of a wheel assembly with ac cording to the present invention being partially clipped for illustrative purposes in a perspective view from a distal side and above; Fig. 6 schematically shows the variation of Fig. 5 in a perspective view from a proximal side and above;

Fig. 7 schematically shows the variation of Fig. 5 in a partially disassembled state in a perspective view from a distal side and above.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many dif ferent forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal reguirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

Fig. 1 to Fig. 4 show a fist variation of a wheel assembly 1 for an electric vehicle comprising a wheel hub motor that is configured to receive two tires (not shown) and e.g. may be used for vehicles having twin tires. As schematically depicted in Fig. 1 and Fig. 2 the wheel assembly 1 therefore comprises a tire reception means 700 comprising two rims 702 to receive two tires. Therefore, both rims 702 comprise a distal and a proximal rime edge 720, 71 0. The wheel assembly 1 is attached to a mount 2 as will be explained in more detail below. The mount 2 is part of a vehicle's steering system and comprises an opening 3 to receive a brake disc 800 that is interconnected with the wheel assembly 1 . The wheel assembly 1 further comprises a stator 1 00 that has a stator housing 1 20 which has a stator housing widened section 1 21 comprising an in general cylindrical shape and that extends in an axial direction x. The stator housing 1 20 of the variation shown is made from a carbon fiber reinforced plastic which allows to reduce total weight of the wheel assembly 1 significantly. In an in axial direction x proximal end 1 22 the stator housing merges into a stator axle 1 1 0 that is hollow and configured to receive electrical cables and/or coolant lines. The stator axle 1 1 0 is arranged coaxially to and extending away from the stator housing 1 20 and has a smaller diameter than the stator hous- ing widened section 1 21 . In the variation shown the stator axle 1 1 0 and the stator housing 1 20 are interconnected with each other by means of a flange connection and a number of connecting means 300 (screws). The stator axle 1 1 0 of the vari ation shown is made from a metallic material. However, for certain applications it may also at least partially be made from a fiber-reinforced plastic or another mate- rial.

The wheel assembly 1 further comprises an electrical winding 230 that is arranged at the stator housing widened section 1 21 to generate a magnetic field for applying torgue on a rotor 200, as subseguently will be explained in more detail. The elec trical winding 1 30 is arranged in a stator cage 1 50 that in the variation shown is embodied as a separate part and is mechanically interconnected with the stator housing 1 20. The stator housing widened section 1 21 encompasses a cavity that constitutes a receiving space 1 40 which is suitable to receive power electronics to operate the magnetic field generated by the electrical winding 1 30. The receiving space 1 30 is accessible from the proximal end 1 22 by means of the hollow stator axle 1 1 0. As well, it comprises a distal opening arranged at its distal end 1 23 which in the Figs is closed by means of a stator closure 61 0. The stator closure is remov ably interconnected with the stator housing 1 20 by means of connecting means 300. The stator closure 61 0 may be removed e.g. for maintenance of components arranged in the receiving space 1 30.

The variation of a wheel assembly 1 as shown in Fig. 1 to Fig. 4 further comprises a rotor 200 which has a rotor housing 220 that is arranged coaxially to and rotat able around the stator 1 00. The rotor housing has a rotor housing widened section 221 that encompasses the stator housing widened section 1 21 at a certain dis tance, forming a small gap between the rotor housing widened section 221 and the electrical winding 1 30 (see Fig. 4). The rotor housing widened section 221 at an in axial direction x proximal end 1 22 merges into a hollow-cylindrical rotor axle 21 0 that has a smaller diameter than the rotor housing widened section 221 . The rotor 200 is supported with respect to the stator axle 1 1 0 by a first proximal bear ing 901 . In addition, the rotor 200 is also supported with respect to the mount 2 by a second proximal bearing 902. Thus, also very high loads can be supported reliably.

As e.g. depicted in Fig. 4, the wheel assembly 1 is encapsulated inter alia by means of a closure arrangement 600 that in addition to the stator closure 61 0 also com prises a rotor closure 620. The rotor closure is supported with respect to the stator 1 00 by at least one distal bearing 903 that is arranged at the stator closure 61 0. Due to such a support on the proximal as well as the distal end/sides 1 22, 1 23 the shown variation of a wheel assembly 1 can be used also for very high loads while inspection, repair and maintenance is still relatively easily possible.

As schematically shown in Fig. 3, in this first variation of wheel assembly 1 shown, the rotor housing widened section 221 is interconnectable with a tire reception means 700 suitable to receive at least one tire and is made from multiple compo nents. The tire reception means 700 comprises two rim-like structures 701 which have a certain geometry to receive tires, as described above. The rotor housing wid ened section 221 therefore comprises a coupling means 701 which is an integral part of the rotor housing 220 and comprises multiple protrusions respectively in dentations extending in axial direction x of the rotor housing widened section 221 and that are distributed circumferentially on the outer surface of the rotor housing widened section 221 . The two rim-like structures 702 have on a centripetal surface multiple protrusions/indentations corresponding to those arranged at the rotor housing widened section 221 and forming a locking element 750 to establish pos itive locking between the rims 702 and the rotor housing widened section 221 in circumferential direction of the rotor housing widened section 221 . As schemati cally shown in Fig. 3, the rims 702 can be removed from the rotor 200 by displac ing them in axial direction x. In order to ensure correct positioning of the two rims 702 with respect to the rotor 200 as well as to each other, the variation shown comprises a centering ring 770 arranged at the rotor housing widening section that constitutes a centering means for the two rims 702. As well, the variation com- prises two positioning rings 760 that serve as positioning means, respectively spac ers, to position the two rims 702 a certain distance apart from each other as well as relatively to the centering ring 770. The two rims 702, the two positioning rings 760 and the centering ring 770 are held in position by means of a proximal and a distal tensioning means 740 that are braced against each other. Therefore, the dis tal tensioning means 740 is embodied as a tensioning ring that can be attached to the rotor housing 220 by means of multiple screws 300. As the rotor 300 carries most loads, the rims 702 can be made very thin-walled if compared to conventional designs and hence total weight can be reduced. As schematically shown in Fig. 4, the rotor housing widened section 221 comprises permanent magnets 230 which are embedded in a housing wall 225 of the rotor housing widened section 221 which is made from carbon-fiber reinforced plastic. In the variation shown, the magnets are positioned such that they align with the protrusions of the locking element 750. Thus, a particularly lightweight wheel as- sembly 1 can be obtained which also has particularly advantageous stress and strain distribution in the rotor housing 220.

Fig. 5 to Fig. 7 schematically show a second variation of a wheel assembly 1 ac cording to the present invention that is suited for being used for singe tire wheels, such as e.g. for automobiles. In contrast to the first variation as schematically shown in Figs. 1 to 4, this wheel assembly 1 the tire reception means 700 of this variation is an integral part of the rotor 200, respectively the rotor housing widened section 221 . Therefore, multiple magnets 230 are embedded in the rim well which is part of the housing wall 225 of the rotor housing widened section 221 . The rotor 200 further comprises a wheel disc 730 comprising multiple spokes 735 and which is supported with respect to the stator axle 1 1 0 by an arrangement of bearings 900, 901 , 902. The spokes serve as structural reinforcements, as well as they serve as cooling ribs to improve cooling of the wheel assembly 1 . In addition the wheel as sembly 1 shown in Figs. 5 to 7 comprises an electrical cable 1 01 and two coolant lines 1 02 in order to provide the wheel assembly with electrical power and to reg ulate the temperature of the wheel assembly before and/or during and/or after operation. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without depart ing from the Spirit and scope of the invention.

LIST OF DESIGNATIONS

1 Wheel assembly 230 Magnet

2 Mount 25 300 Connecting means

3 Opening (for brake) (screws)

1 00 Stator 500 Power electronics

1 01 Electrical wire 600 Closure arrangement

1 02 Coolant line 61 0 Stator closure

1 1 0 Stator axle 30 620 Rotor closure

1 20 Stator housing 700 Tire reception meanso 1 21 Stator housing widened 701 Coupling means

section 702 Rim

1 22 Proximal end 71 0 Proximal rim edge

1 23 Distal end 35 720 Distal rim edge

1 25 Stator housing wall 730 Wheel disc

5 1 30 Electrical winding (coil) 735 Spokes

1 40 Receiving space 740 Tensioning means

1 50 Stator cage 750 Locking element (protru

200 Rotor 40 sions/indentations)

21 0 Rotor axle 760 Positioning means0 220 Rotor housing 770 Centering means

221 Rotor housing widened 800 Brake disc

section 900 Bearing

225 Rotor housing wall 45 901 First proximal bearing Second proximal bearing Distal bearing