GB2522907A - Improvements in or relating to wheel hub electric motors - Google Patents

Abstract

A wheel hub electric motor assembly 10 for a wheeled vehicle. The wheel hub electric motor assembly 10 comprises an electric motor 18 having a rotor 36, a stator 34 and a hub assembly (21, Figure 5) having formations which enable a vehicle wheel to be connected thereto. The hub assembly (21) has a base member 76, a rotor member 78 and bearing 80 disposed therebetween. The base member 76 of the hub assembly (21) is releasably connected to the stator 34. The rotor member 78 of the hub assembly (21) is coupled for rotation with the rotor 36 of the electric motor 18. The wheel hub electric motor assembly 10 further includes a bearing arrangement 64 provided between the rotor 36 and the stator 34 of the electric motor 18. Preferably the hub assembly (21) can be removed from a wheel hub electric motor assembly 10 without affecting the alignment if the rotor 36 and stator 34, the alignment of the rotor 36 and stator 34 being maintained by the bearing arrangement 64.

Description

Improvements in or relating to wheel hub electric motors S The present invention relates to wheel hub electric motor assembly and in particular to wheel hub electric motor assembly for use with a road vehicle.

Wheel hub electric motor assemblies are finding increasing use in electric and hybrid powered road vehicles. Such assemblies are provided in the space defined between the interior of a vehicle heel and the hub to which the wheel is connected, in use and are used to drive the wheel directly.

According to a first aspect of the present invention there is provided a wheel hub electric motor assembly for a wheeled vehicle, the wheel hub electric motor assembly comprising an electric motor having a rotor and a stator, and a hub assembly having formations which enable a vehicle wheel to be connected thereto, the hub assembly having a base member, a rotor member and bearing disposed ihierebetween, ihe base member of the hub assembly being releasably connected to the stator, and the rotor member of the hub assembly being coupled for rotation with the rotor of the electric motor, wherein the wheel hub electric motor assembly further includes a bearing arrangement provided between the rotor and the stator of the electric motor.

In a preferred embodiment, the bearing arrangement is provided between co-axially aligned annular portions of the rotor and stator.

The hub assembly may be removable from the wheel hub electric motor assembly without affecting the alignment of the rotor with respect to the stator. Upon removal of the hub assembly, alignment of the rotor with respect to the stator is maintained by the bearing arrangement.

The rotor member of the hub assembly may be coupled for rotation with the rotor of the elecific motor by an annular coupling ring which is fixed for rotation with the rotor member of the hub assembly. In such an embodiment, the coupling ring may be provided with a plurality of formations which, in use, align with a complimentary plurality of formations of the rotor. Drive members may be located between the formations in order to rotationally couple the hub assembly to the rotor.

The wheel hub electric motor assembly may further be provided with a brake disc which is connected to the rotor.

The wheel hub electric motor assembly may further include a vehicle suspension component which is connected to stator of the electric motor. The vehicle suspension component may be a lower suspension knuckle. The lower suspension knuckle may be provided with a through aperture which provides access to the stator. The through aperture may be utilised to route conduits to the stator, which conduits effect operation of the electric motor. Such conduits may include, for example, cooling fluid conduits and electrical power transmission conduits.

The wheel hub electric motor assembly may further include a disc brake caliper. The caliper may advantageously be mounted to the lower suspension knuckle.

According to a second aspect of the present invention there is provided a vehicle including a wheel hub electric motor assembly according to the first aspect.

An embodiment of the present invention will now be described with reference to the accompanying figures in which: Figure 1 is a front view of a wheel hub electric motor assembly according to the present invention; Figure 2 is a side view of the wheel hub electric motor assembly of figure 1; Figure 3 is a rear view of the wheel hub electric motor assembly of figure 1; Figure 4 is a partial cross-sectional view of the wheel hub electric motor assembly as indicated by line A-A on figure 1; and Figure 5 shows an exploded view of the wheel hub electric motor assembly.

Referring to the figures there is shown a wheel hub electric motor assembly generally designated 10. The assembly 10 includes mounting member referred to hereinafter as a lower knuckle 12, a brake disc 14, a single piston floating brake calliper 16 and an electric motor generally designated 18. The electric motor 18 will be described in greater detail below. The assembly 10 further includes a plurality of wheel studs 20 which, in use, enable a wheel to be fitted to the assembly 10 and be retained in association with the assembly 10 by the provision of a plurality of wheel nuts (not shown), The wheel studs 20 are carried by a hub assembly 2]. In an alternative embodiment the hub assembly 21 may be provided with threaded holes configured to receive wheel bolts.

The lower knuckle] 2 permits the assembly] 0 to be mounted to the suspension arrangement of a vehicle. To facilitate such mounting the lower knuckle 12 is provided with a plurality of through apertures 22 which enable the lower knuckle 12 to be connected to suspension components of a vehicle by appropriate fixing means, for example nut and bolt pairs. It will be appreciated that the configuration of the lower knuckle 12, and thus the location and spacing of the through apertures 22, is dependent upon the suspension configuration of the vehicle to which the assembly 10 is to be fitted, As such, it will be appreciated by the reader that the configuration of the knuckle U shown in the figures is illustrative and not limiting. The knuckle]2 may be formed from a machined metal casting. Alternatively, the knuckle 12 may be machined from billet.

The lower knuckle 12 is further provided with a flange 24 to which the brake calliper 16 is mounted, The flange 24 is provided with a pair of through apertures 26 which align with corresponding apertures of the brake calliper 16. The brake calliper]6 is connected to the flange 24 by bolts 28.

The lower knuckle 12 is further provided with a substantially centrally located through aperture 30. The through aperture 30 permits electrical power conduits 32 and liquid coolant conduits to extend through the lower knuckle] 2 to the electric motor 18. The through aperture 30 may also accommodate a drive shaft (not shown) which connects to the hub assembly 21.

The electric motor 18 includes a stator generally designated 34 and a rotor generally designated 36. Looking firstly at the stator 34, this comprises a substantially dish shaped member 38 having a wall 40 and a base 42. The dish shaped member 38 includes a larger diameter portion 44 and a smafler diameter portion 46. Tn the embodiment shown, the smaller diameter portion 46 is defined by the base 42 and the larger diameter portion 44 by the wall 40 The wall 40 of the dish shaped member 38 further defines an interior space 48, The base 42 is further provided with a through aperture 50.

The outer periphery 52 of the larger diameter portion 44 is substantially cylindrical.

Located around outer periphery 52 of the larger diameter portion 44 of the stator 34 are the windings 54 of the stator 34. The windings 54 are mounted to an annular band 56 which is fitted to the outer periphery of the stator 34. The underside of the annular band 56, which is to say the side of the annular band 56 which faces the outer periphery 52 of the larger diameter portion 44 of the stator 34, is provided with a plurality of circumferential recesses 58. The recesses 58 of the annular band 56 co-operate with the outer periphery 52 of the larger diameter portion 44 of the stator 34 to define a plurality of coolant channels, In use, liquid coolant can be circulated through the coolant channels in order to cool the windings 54, Coolant is passed to and from the coolant channels via internal conduits provided within the base 42 and wall 40 of the stator 34, The internal conduits terminate at coolant conduit connectors 60 provided on the base 42 and which, in use, project into the through aperture 30 of the lower knuckle 12.

The outer periphery 62 of the smaller diameter portion 46 of the stator 34 is also substantially cylindrical. As will be described in greater detail below, the outer periphery 62 of the smaller diameter portion 46 of the stator 34 supports the inner race of a bearing arrangement 64.

In use, the stator 34 is rigidly connected to the lower knuckle 12, In the embodiment shown the stator 34 is connected to the lower knuckle 12 by a plurality of bolts 66.

The bolts 66 extend through apertures 68 present in the lower knuckle 12 and into threaded holes 70 present in the base 42 of the stator 34. It will be understood that when the stator 34 is connected to the lower knuckle 12, then the through aperture 50 of the base 42 aligns with the through aperture 30 of the lower knuckle 12.

The stator 34 is further provided electrical connectors 72 which enable the aforementioned electrical power conduits 32 to be connected to the windings 54. The electrical connectors are located on the base 42 of the stator 34 and within the interior space 48. The stator 34 is ifirther provided with a rotation sensor 74 which, in use, senses rotation of the rotor 36 relative to the stator 34. The rotation sensor 74 is within the interior space 48 of the stator 34.

The dish shaped member 38 of the stator 34 is manufactured from a non-ferrous metal such as, for example, aluminium alloy. The dish shaped member 38 may preferably be machined from solid.

The hub assembly 21 is of a conventional type, for example an X Tracker unit manufactured by SKF. The hub assembly 21 includes a base member 76 and a rotor member 78. Interposed between the base and rotor members 76,78 is a double row angular contact bearing arrangement 80 which permits the rotor member 78 to rotate relative to the base member 76. The rotor member 78 includes a circular peripheral flange 82 which carries the wheel studs 20. The rotor member 78 is further provided with a splined through aperture 84 to which a correspondingly splined drive shaft may be fitted.

The base member 76 of the hub assembly 21 is rigidly connected to the base 42 of the stator 34 by three bolts 86. The bolts 86 extend through apertures provided in the base 42 of the stator 34 and into threaded holes of the hub assembly base member 76. The heads of the bolts 86 are accessible through the central through aperture 30 of the lower knuckle 12 or through smaller purpose provided apertures 70' in the lower knuckle 12. This enables the hub assembly TI to be disconnected from the stator 34 without the need for the stator 34 to be disconnected from the lower knuckle U. The rotor 36 includes an annular dished member 88 and an annular backing plate 90.

The annular dished member 88 and annular backing plate 90 are also manufactured from a non-ferrous metal such as, for example, aluminium alloy. In the embodiment shown, the annular backing plate 90 is releasably connected to the annular dished member 88 by a plurality of threaded fasteners 92. The threaded fasteners 92 extend through apertures 94 of the backing plate 90 which are aligned with blind threaded recesses 96 of the annular dished member 88. It will be understood that the provision of the threaded fasteners 92 enables both encapsulation of the stator 34 by the rotor 36 during assembly of the electric motor 18, and the subsequent possible removal of the annular dished member 88 from the wheel hub motor assembly 10. In an alternative embodiment, the annular backing plate 90 may be permanently connected to the annular dished member 88, for example by welding.

The annular dished member 88 includes a central aperture 89. The central aperture 89 is circular and has a diameter that is slightly greater than the circular flange 82 of the hub assembly 21. As can be seen in figure 4, the circular flange 82 is received in the central aperture 89 of the annular dished member 88. As noted above, the hub assembly 21 can be disconnected from the stator 34 without the need to disconnect the stator 34 from the knuckle 12. The circular flange 82 and central aperture 89 are dimensioned such that the hub assembly 21 can be withdrawn through the central aperture 89 without requiring the rotor 36 to be separated from the stator 34.

Positioned around the inner periphery of the 98 of the annular dished member 88 are a plurality of magnets 100. The magnets 100 are provided upon a support ring 102 which is fixed to the inner periphery 98 of the annular dished member 88. The support ring 102 may be fixed to the inner periphery 98 by, for example, an interference fit.

It will be appreciated that the minimum inner diameter of the annular dished member 88, support ring 02 and magnets 100 is greater than the maximum outer diameter of the stator 34 and windings 54, with the result that there exists a clearance gap 104 between the magnets 100 and the windings 54. The clearance gap 104 may be approximately 1mm. It will be understood that in order for the electric motor 18 to operate effectively, the clearance gap 104 must be maintained at all times. It will further be understood that contact between the windings 54 and the magnets 100 must be avoided so as to prevent significant damage being done to either the windings 54 or magnets 100.

In order for the rotor 36 of the electric motor 18 to be able to impart rotational torque to a vehicle wheel fitted to the wheel studs 20, the rotor 36 has to be connected to the rotor member 78 of the hub assembly 2]. In the present invention, this connection is achieved by a coupling disc 106. In the embodiment shown, the coupling disc 106 is annular and is provided with a central aperture 108. The coupling disc 106 is further provided with a plurality of equidistantly spaced through apertures 110 which surround the central aperture 108. The number and spacing of the through apertures corresponds to the number and spacing of the wheel studs 20 on the hub assembly 21. The diameter of the through apertures 110 is chosen such that the coupling disc 106 is able to fit over the wheel studs 20 as can be seen in figure 4.

The annular dished member 88 of the rotor 36 is provided with a recess 112 which surrounds the central aperture 89 of the annular dished member 88. The recess 112 has a depth that is approximately equal to the thickness of the coupling disc 106. The coupling disc 106 thus a flush fit to the recess] ] 2 as can be seen in figure 4.

The coupling disc 106 is further provided with a countersunk set screw aperture 114 which is alignable with a threaded setscrew hole provided in the circular flange 82 of the hub assembly 21. The coupling disc 106 can thus be retained to the hub assembly 21 by a countersunk set screw 116 when the vehicle wheel is removed.

Spaced around the periphery 118 of the coupling disc 106 are a plurality of part circular recesses 120. Each recess 120 of the coupling disc aligns with a thrther part circular recess 122 of the annular dished member 88 when the coupling disc 106 is fitted to the hub assembly 2L Each recess pair]20,]22 cooperates to define a substantially circular recess within which a drive pin 124 is received to rotationally connect the rotor 36 to the hub assembly 21 through the coupling disc 106.

Referring once again to the annular backing plate 90 of the rotor 36, the backing plate includes a tubular part 126 having a circular flange 128 provided at one end. The aforementioned through apertures 94 are provided in the flange 128. The outer diameter of the tubular part 126 is less than the outer diameter of the flange 128. The annular backing plate 90 is further provided with a central through aperture 130. The central through aperture 130 has a diameter that is greater than the diameter of outer periphery 62 of the smaller diameter portion 46 of the stator 34. h use, and as can be seen from figure 4, the smaller diameter portion 46 of the stator 34 is received in the central through aperture 130 of the annular backing plate 90. Disposed between the smaller diameter portion 46 of the stator 34 and the central through aperture 130 of the annular backing plate 90 is the bearing arrangement 64.

In the embodiment shown, the bearing arrangement 64 is comprised of two single row bearings 64a, 64b. The inner bearing 64a, which is to say the bearing closest to the knuckle 12 is retained between a lip 132 provided on the tubular part 126 of the annular backing plate 90 and a retaining ring 134 that is fixed to the stator 34, The retaining ring 134 is fixed to the stator 134 by threaded fasteners 136 which extend through apertures 138 of the retaining ring 134 and into threaded holes 140 of the stator 34. The outer bearing 64b, which is to say the bearing furthest from the knuckle 12 is retained between a lip 142 provided on the tubular part 126 of the annular backing plate 90 and a spacing ring 144 which abuts a shoulder 146 of the stator 34.

Annular dust seals 148,150 are provided on opposing sides of the bearing arrangement 63 between the tubular part 126 of the annular backing plate 90 and the stator 34.

It will be understood that in ahernative embodiments of the present invention that alternative bearing arrangements may be utilised. For example, instead of two single row bearings 64a,64b, a single double row bearing may be used.

The brake disc 14 includes an annular braking portion 152 which, in use, interacts with the brake pads of the brake caliper 16. Around the inner periphery of the annular braking portion 152 there are provided a plurality of equidistantly spaced webs 54.

Each web 154 includes a through aperture 156 which aligns, in use, with a corresponding threaded hole 158 provided in the tubular part 126 of the annular backing plate 90. The brake disc 14 is connected to the rotor 36 by threaded fasteners which pass through the apertures 156 and into the holes 158.

As will be appreciated from the description and accompanying drawings, the rotor 36 is supported for rotation relative the stator 34 at two separate bearing locations.

Firstly, the rotor 36 is supported for rotation directly by the stator 34 through the bearing arrangement 64. Secondly, the rotor 36 is supported for rotation indirectly by the stator 34 through the hub assembly 2L This is in contrast to prior art wheel hub electric motor systems where the rotor is supported for rotation relative to the stator by the hub assembly. This necessitates the strengthening of the hub in order to ensure that the correct spacing between the motor windings and magnets is maintained in all operational states of the vehicle. Typically this will require a bespoke hub assembly to be designed and manufactured, and which adds cost to the vehicle to which the hub motor assembly is fitted. The present invention thus provides a wheel hub electric t5 motor which utilises a conventional "off the shelf' hub assembly.

By supporting the rotor 36 for rotation relative the stator 34 at two separate bearing locations, then the risk of touchdown between the rotor 36 and stator 34, with the almost inevitable damage to the magnets and/or windings of the electric motor, is reduced, It will further be appreciated that, in use, wheel impact loads are not transferred directly to the rotor 36.

By supporting the rotor 36 for rotation relative the stator 34 at two separate bearing locations, then an advantage relating to the servicing and repair of the wheel hub electric motor assembly tO is enabled. Specifically, the hub assembly 2t can be removed and refitted without affecting the alignment of the rotor 36 and stator 34.

Upon removal of the hub assembly 21, rotor 36 and stator 34 alignment is maintained by the bearing arrangement 64.

While in the embodiment shown the wheel hub electric motor assembly 10 is configured for use with a non-mechanically driven wheel and a non-steerable wheel of a vehicle, it will be appreciated that the bearing arrangement 64 of the present invention may be incorporated into driven and/or steerable wheel hub electric motor assemblies.