An electric machine

Abstract

An electric machine (10) comprising a stator (20) having a cylindrical inner channel (30) with a central stator axis (32), and a rotor (50) coaxially located within the cylindrical inner channel (30) of the stator (20), the rotor (50) and stator (20) being located, at least in part, within a motor housing (70), wherein the electric machine (10) comprises: a first tubular section (80) having a first end (82) of circular cross section and a second end (84) of circular cross section, the first end (82) of the first tubular section (80) located at a first end (72) of the motor housing (70) and the second end (84) of the first tubular section (80) located at a first end (22) of the stator (20); and a second tubular section (180) having a first end (182) of circular cross section and a second end (184) of circular cross section, the first end (182) of the second tubular section (180) located at a second end (172) of the motor housing (70) and the second end (184) of the second tubular section (180) located at a second end (122) of the stator (20).

Description

[0001] AN ELECTRIC MACHINE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to an electric machine. Particularly, but not exclusively, the present disclosure relates to an electric machine with an oil retention arrangement that can be used to maintain oil of an electric machine cooling system away from a rotor of the electric machine.

[0004] Aspects of the invention relate to an electric machine, and to a vehicle.

[0005] BACKGROUND

[0006] It is known to use one or more electric machine in the operation of land, sea, and air vehicles. In operation, each electrical machine can be provided with electrical energy to provide a motive or tractive force to a vehicle in order to propel the vehicle. Such electric machines may also be arranged to operate as generators to generate electrical energy, for example by the use of such an electric machine in a regenerative braking system of the vehicle. Electric machines may be used in place of an internal combustion engine in a battery electric vehicle (BEV), or in addition to an internal combustion engine in a plug-in hybrid electric vehicle (PH EV) or a hybrid electric vehicle (HEV).

[0007] An electric machine, for example a permanent magnet synchronous motor, comprises a rotor and a stator, separated by a small air gap. The stator provides a stationary element of the electric machine and may be formed from a series of stator laminations to form a cylindrical stator body. The stator comprises a plurality of slots along the cylindrical stator body, parallel with a central stator axis, within which electrical windings are located. The rotor, which is located within a cylindrical inner channel of the stator provides a rotating element allowing an electrical energy input to be converted to a mechanical output, for example to provide rotation of a driveshaft of the vehicle. When operating as a generator, a mechanical input can be converted to an electrical energy output by the electric machine.

[0008] It is desirable to operate the electric machine within certain parameters, for example within certain temperature limits, to avoid undue wear and fatigue on the electric machine. Such electric machines when used as a motor and / or generator on a vehicle may therefore be cooled by passing a coolant through a coolant arrangement, such as a coolant jacket on the electric machine housing.

[0009] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

[0010] SUMMARY OF THE INVENTION

[0011] Aspects and embodiments of the invention provide an electric machine, and a vehicle as claimed in the appended claims.

[0012] According to an aspect of the present invention there is provided an electric machine comprising a rotor and a stator, the rotor and the stator being located, at least in part, within a motor housing, wherein the electric machine comprises a tube arrangement configured or arranged to segregate or isolate components of the stator from the rotor. The tube arrangement has a first end of circular cross section and a second end of circular cross section, the first end abutting a first end of the motor housing and the second end abutting a second end of the motor housing.

[0013] According to an aspect of the present invention there is provided an electric machine comprising a stator having a cylindrical inner channel with a central stator axis, and a rotor coaxially located within the cylindrical inner channel of the stator, the rotor and stator being located, at least in part, within a motor housing, wherein the electric machine comprises: a first tubular section having a first end of circular cross section and a second end of circular cross section, the first end of the first tubular section located at a first end of the motor housing and the second end of the first tubular section located at a first end of the stator; and a second tubular section having a first end of circular cross section and a second end of circular cross section, the first end of the second tubular section located at a second end of the motor housing and the second end of the second tubular section located at a second end of the stator.

[0014] An advantage of this aspect of the invention is that the stator can be segregated from the rotor such that a cooling fluid or coolant media can be provided to the stator without such cooling fluid or coolant media contacting the rotor. The second end of the first tubular section may have an outer diameter substantially equal to the diameter of the cylindrical inner channel of the stator at the first end of the stator and the second end of the second tubular section may have an outer diameter substantially equal to the diameter of the cylindrical inner channel of the stator at the second end of the stator.

[0015] The motor housing may comprise a first bearing housing at the first end of the motor housing against which the first end of the first tubular section is engaged.

[0016] The first bearing housing may comprise a section extending axially, parallel with the central stator axis, and against which an inner surface of the first end of the first tubular section may be engaged.

[0017] The axially extending section of the first bearing housing may be circular in cross section and may comprise an O-ring seal channel, around the circumference of the axially extending section of the first bearing housing, configured to retain an O-ring, wherein the O-ring may be located between the axially extending section of the first bearing housing and the inner surface of the first end of the first tubular section.

[0018] The axially extending section of the first bearing housing may comprise a plurality of O-ring seal channels around the circumference of the axially extending section of the first bearing housing, each configured to retain an O-ring.

[0019] The motor housing may comprise a second bearing housing at the second end of the motor housing against which the first end of the second tubular section may be engaged.

[0020] The second bearing housing may comprise a section extending axially, parallel with the central stator axis, and against which an inner surface of the first end of the second tubular section may be engaged.

[0021] The axially extending section of the second bearing housing may be circular in cross section and comprise an O-ring seal channel, around the circumference of the axially extending section of the second bearing housing, configured to retain an O-ring, wherein the O-ring may be located between the axially extending section of the second bearing housing and the inner surface of the first end of the second tubular section. The axially extending section of the second bearing housing may comprise a plurality of Coring seal channels around the circumference of the axially extending section of the first bearing housing, each configured to retain an O-ring.

[0022] A terminal end of the first end of the stator may comprise a chamfered section such that the inner diameter of the stator at the terminal end of the first end of the stator is larger than the inner diameter of a central section of the stator. A terminal end of the second end of the stator may comprise a chamfered section such that the inner diameter of the stator at the terminal end of the second end of the stator is larger than the inner diameter of the central section of the stator.

[0023] The second end of the first tubular section may comprise a chamfered section having an outer diameter less than the diameter of the cylindrical inner channel of the stator at the first end of the stator. The second end of the second tubular section may comprise a chamfered section having an outer diameter less than the diameter of the cylindrical inner channel of the stator at the second end of the stator.

[0024] The electric machine may comprise a guide located at the first end of the stator. The guide may comprise a chamfered section tapering towards the cylindrical inner channel of the stator.

[0025] The first end of the stator, proximal to the first tubular section, may comprise a first stator section and a second stator section, the first stator section of the first end of the stator being closer than the second stator section of the first end of the stator to a terminal end of the first end of the stator and providing a section of increased diameter bore in the cylindrical inner channel of the stator relative to the second stator section of the first end of the stator. The first stator section of the first end of the stator may be configured to receive a length of the second end of the first tubular section to provide an overlap of the stator and the first tubular section parallel to the central stator axis.

[0026] The increased diameter bore at the first stator section of the first end of the stator may be provided by a plurality of stator laminations each having an increased diameter central aperture when compared to stator laminations of the second stator section of the first end of the stator located further from the terminal end of the first end of the stator.

[0027] The length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis may engage with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement. An axial seal may be provided between a terminal end of the second end of the first tubular section and the second stator section of the first end of the stator.

[0028] The first end of the stator, proximal to the first tubular section, may comprise a first stator section and a second stator section, the first stator section of the first end of the stator being closer than the second stator section of the first end of the stator to a terminal end of the first end of the stator. A first end of the rotor, proximal to the first tubular section, may comprise a first rotor section and a second rotor section, the second rotor section of the first end of the rotor being closer than the first rotor section of the first end of the rotor to a terminal end of the first end of the rotor and providing a section of decreased diameter rotor relative to the first rotor section of the first end of the rotor, the second rotor section of the first end of the rotor being configured to allow an overlap of the first stator section of the stator and the first tubular section parallel to the central stator axis.

[0029] The first stator section of the first end of the stator may be configured to receive a length of the second end of the first tubular section to provide an overlap of the stator and the first tubular section parallel to the central stator axis.

[0030] The section of decreased diameter rotor may provide a clearance gap between the rotor and the first tubular section when the first tubular section overlaps the stator parallel to the central stator axis.

[0031] The length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis may engage with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

[0032] The length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis may engage with an O-ring seal positioned between the second end of the first tubular section and the inner surface of the cylindrical inner channel of the stator.

[0033] The length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis may engage with a plurality of O-ring seals positioned between the second end of the first tubular section and the inner surface of the cylindrical inner channel of the stator. The first tubular section may comprise a first portion of a first thickness and a second portion of a second thickness. The second portion of the first tubular section may comprise a length of the second end of the first tubular section configured to overlap the stator parallel to the central stator axis. The thickness of the first portion of the first tubular section may be greater than the thickness of the second portion of the first tubular section.

[0034] An axial seal may be provided between the end of the first portion of the first tubular section, closest to the first end of the stator, and a terminal end of the first end of the stator.

[0035] The first rotor section of the first end of the rotor and the second rotor section of the first end of the rotor may comprise different rotor configurations. The first rotor section of the first end of the rotor may have a higher reluctance torque than the second rotor section of the first end of the rotor. The first rotor section of the first end of the rotor may comprise a high reluctance torque permanent magnet rotor. The first rotor section of the first end of the rotor may comprise a multi-layer barrier structure that houses permanent magnet sections. The first rotor section of the first end of the rotor may exhibit reluctance torque in the range of 40% to 80%. The second rotor section of the first end of the rotor may comprise a high magnet-excitation torque rotor. The second rotor section of the first end of the rotor may comprise larger magnet sections in a structure where reluctance torque is <20%.

[0036] The first end of the rotor may be shorter than the first end of the stator along the direction of the central stator axis to allow an overlap of the stator and the first tubular section parallel to the central stator axis.

[0037] The first stator section of the first end of the stator may be configured to receive a length of the second end of the first tubular section to provide an overlap of the stator and the first tubular section parallel to the central stator axis.

[0038] The length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis may engage with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

[0039] There may be no rotor located axially along the direction of the central stator axis that radially overlaps with the length of the second end of the first tubular section when the length of the second end of the first tubular section overlaps the stator.

[0040] The second end of the first tubular section may be adhered to the first end of the stator. The axially outer lamination of the stator at the first end of the stator may have a smaller inner diameter to provide a surface on which to adhere the second end of the first tubular section.

[0041] Adherence between the second end of the first tubular section and the first end of the stator may be provided by a welded connection.

[0042] The welded connection may be a friction weld or a laser weld.

[0043] The first tubular section may comprise a sleeve and a toothed disc. The toothed disc may be located at the second end of the first tubular section and may be joined to the sleeve. The toothed disc may comprise a plurality of teeth configured to overlap respective teeth of the stator when the first tubular section is located at the first end of the stator.

[0044] The toothed disc which may be located at the second end of the first tubular section may be overmoulded onto the sleeve.

[0045] The toothed disc may form a labyrinth mask providing a passage therethrough.

[0046] The second end of the stator, proximal to the second tubular section, may comprise a first stator section and a second stator section, the first stator section of the second end of the stator being closer than the second stator section of the second end of the stator to a terminal end of the second end of the stator and providing a section of increased diameter bore in the cylindrical inner channel of the stator relative to the second stator section of the second end of the stator. The first stator section of the second end of the stator may be configured to receive a length of the second end of the second tubular section to provide an overlap of the stator and the second tubular section parallel to the central stator axis.

[0047] The increased diameter bore at the first stator section of the second end of the stator may be provided by a plurality of stator laminations each having an increased diameter central aperture when compared to stator laminations of the second stator section of the second end of the stator located further from the terminal end of the second end of the stator.

[0048] The length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis may engage with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement. An axial seal may be provided between a terminal end of the second end of the second tubular section and the second stator section of the first end of the stator.

[0049] The second end of the stator, proximal to the second tubular section, may comprise a first stator section and a second stator section, the first stator section of the second end of the stator being closer than the second stator section of the second end of the stator to a terminal end of the second end of the stator. A second end of the rotor, proximal to the second tubular section, may comprise a first rotor section and a second rotor section, the second rotor section of the second end of the rotor being closer than the first rotor section of the second end of the rotor to a terminal end of the second end of the rotor and providing a section of decreased diameter rotor relative to the first rotor section of the second end of the rotor, the second rotor section of the second end of the rotor being configured to allow an overlap of the first stator section of the second end of the stator and the second tubular section parallel to the central stator axis.

[0050] The first stator section of the second end of the stator may be configured to receive a length of the second end of the second tubular section to provide an overlap of the stator and the second tubular section parallel to the central stator axis.

[0051] The section of decreased diameter rotor may provide a clearance gap between the rotor and the second tubular section when the second tubular section overlaps the stator parallel to the central stator axis.

[0052] The length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis may engage with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

[0053] The length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis may engage with an O-ring seal positioned between the second end of the second tubular section and the inner surface of the cylindrical inner channel of the stator.

[0054] The length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis may engage with a plurality of O-ring seals positioned between the second end of the second tubular section and the inner surface of the cylindrical inner channel of the stator. The second tubular section may comprise a first portion of a first thickness and a second portion of a second thickness. The second portion of the second tubular section may comprise a length of the second end of the second tubular section configured to overlap the stator parallel to the central stator axis. The thickness of the first portion of the second tubular section may be greater than the thickness of the second portion of the second tubular section.

[0055] An axial seal may be provided between the end of the first portion of the second tubular section, closest to the second end of the stator, and a terminal end of the second end of the stator.

[0056] The first rotor section of the second end of the rotor and the second rotor section of the second end of the rotor may comprise different rotor configurations. The first rotor section of the second end of the rotor may have a higher reluctance torque than the second rotor section of the second end of the rotor. The first rotor section of the second end of the rotor may comprise a high reluctance torque permanent magnet rotor. The first rotor section of the second end of the rotor may comprise a multi-layer barrier structure that houses permanent magnet sections. The first rotor section of the second end of the rotor may exhibit reluctance torque in the range of 40% to 80%. The second rotor section of the second end of the rotor may comprise a high magnet-excitation torque rotor. The second rotor section of the second end of the rotor may comprise larger magnet sections in a structure where reluctance torque is <20%.

[0057] The second end of the rotor may be shorter than the second end of the stator along the direction of the central stator axis to allow an overlap of the stator and the second tubular section parallel to the central stator axis.

[0058] The first stator section of the second end of the stator may be configured to receive a length of the second end of the second tubular section to provide an overlap of the stator and the second tubular section parallel to the central stator axis.

[0059] The length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis may engage with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

[0060] There may be no rotor located axially along the direction of the central stator axis that radially overlaps with the length of the second end of the second tubular section when the length of the second end of the second tubular section overlaps the stator. The second end of the second tubular section may be adhered to the second end of the stator.

[0061] The axially outer lamination of the stator at the second end of the stator may have a smaller inner diameter to provide a surface on which to adhere the second end of the second tubular section.

[0062] Adherence between the second end of the second tubular section and the second end of the stator may be provided by a welded connection.

[0063] The welded connection may be a friction weld or a laser weld.

[0064] The second tubular section may comprise a sleeve and a toothed disc. The toothed disc may be located at the second end of the second tubular section and may be joined to the sleeve. The toothed disc may comprise a plurality of teeth configured to overlap respective teeth of the stator when the first tubular section is located at the second end of the stator.

[0065] The toothed disc which may be located at the second end of the second tubular section may be overmoulded onto the sleeve.

[0066] The toothed disc may form a labyrinth mask providing a passage therethrough.

[0067] The first tubular section may be joined to the second tubular section via a third tubular section the third tubular section extending from the first end of the stator to the second end of the stator.

[0068] The third tubular section may have a thickness less than the first tubular section and the second tubular section.

[0069] The first tubular section may have an inner diameter smaller than the inner diameter of the second tubular section and the third tubular section. The inner diameter of the second tubular section may be equal to the inner diameter of the third tubular section. The outer diameter of the second tubular section may be larger than the outer diameter of the first tubular section and the third tubular section. The outer diameter of the first tubular section may be equal to the outer diameter of the third tubular section. The stator may comprise slots parallel to the central stator axis for retaining electrical windings, wherein apertures are provided between the electrical windings and the slots allowing oil to pass through the slots from an oil inlet to an oil outlet.

[0070] The stator may additionally comprise a plurality of cooling ducts through the stator, each of the plurality of cooling ducts extending substantially parallel to the central stator axis, from the first end of the stator to the second end of the stator.

[0071] The oil inlet may be at the first end of the stator and the oil outlet may be at the second end of the stator.

[0072] The oil inlet may be positioned centrally in the stator between the first end of the stator and the second end of the stator. The stator may comprise a first oil outlet at the first end of the stator and a second oil outlet at the second end of the stator.

[0073] The stator may be formed of an inner stator and an outer stator wherein the inner stator is formed of a continuous array of inner stator laminations from the first end of the stator to the second end of the stator, and the outer stator is formed of a first set of outer stator laminations and a second set of outer stator laminations, the first set of laminations being separated from the second set of laminations to form the oil inlet.

[0074] A first set of the plurality of cooling ducts may extend through the first set of outer laminations from the oil inlet to the first oil outlet and a second set of the plurality of cooling ducts may extend through the second set of outer laminations from the oil inlet to the second oil outlet.

[0075] An advantage of this aspect of the invention is that cooling fluid, or coolant media, can be passed through the stator from a first end of the stator to a second end of the stator in order to transport heat generated by the electrical stator windings in the plurality of winding slots of the stator away from the electric machine, whilst maintaining the rotor in a dry condition.

[0076] An outer surface of the stator may comprise channels parallel to the central stator axis to facilitate the passage of oil across the surface of the stator.

[0077] The stator may comprise winding slots extending parallel to the central stator axis, the winding slots each comprising a material bridge configured to provide a respective radially inner aperture for the passage of oil. Each material bridge may be asymmetrical and comprise a first portion comprising a first surface inside the winding slot and a second portion comprising a second surface inside the winding slot, the first surface and the second surface being radially separated by a third portion comprising a third surface. The third surface may comprise a first curved section extending from an end of the first surface and a second curved section extending from an end of the second surface. At least a portion of the second curved section may overlap one or more of the first surface and the first curved section along an axis parallel to the first surface.

[0078] According to an aspect of the present invention there is provided a method of manufacture of a stator comprising: stamping a stator lamina ring to form an inner ring and an outer ring, the inner ring comprising a plurality of radially projecting teeth, each tooth being connected to adjacent teeth by respective material bridges at radially inner ends of the teeth, and being separated from the adjacent teeth by respective winding slots, wherein the winding slots of the inner ring are open at radially outer ends of the teeth; wherein, the radially outer end of at least one tooth is formed to comprise a first locating feature, the first locating feature being configured to be rotated in a circumferential direction by half of the separation between the centre of adjacent teeth and to abut, or be in an interference engagement with, a second locating feature in the outer ring; and wherein the outer ring, at the location from where the teeth of the inner ring are stamped and separated from the outer ring, is enlarged to form a cooling fluid channel through the winding slot.

[0079] According to an aspect of the present invention there is provided a vehicle comprising an electric machine according to any preceding aspect.

[0080] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0081] BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0082] Figure 1 illustrates a cross sectional image of an electric machine according to an embodiment of the invention;

[0083] Figure 2 illustrates a cross sectional image of an electric machine according to an embodiment of the invention;

[0084] Figure 3 illustrates a cross sectional image of an electric machine according to an embodiment of the invention;

[0085] Figure 4 illustrates a cross sectional image of an electric machine according to an embodiment of the invention;

[0086] Figure 5 illustrates a cross sectional image of an electric machine according to an embodiment of the invention;

[0087] Figure 6 illustrates a cross sectional image of a tube according to an embodiment of the invention;

[0088] Figure 7 illustrates a partial cross sectional image of an electric machine having a guide according to an embodiment of the invention;

[0089] Figure 8 illustrates a partial perspective view of an electric machine according to an embodiment of the invention;

[0090] Figure 9 illustrates a perspective view of a tube according to an embodiment of the invention;

[0091] Figure 10 illustrates a cross sectional view of the tube of Figure 9 according to an embodiment of the invention;

[0092] Figure 11 illustrates an end view of the tube of Figure 9 according to an embodiment of the invention;

[0093] Figure 12 illustrates a perspective view of a tube according to an embodiment of the invention; Figure 13 illustrates a perspective view of the tube of Figure 12, illustrating a cooling fluid path, according to an embodiment of the invention;

[0094] Figure 14 illustrates perspective end view of the tube of Figure 12 and Figure 13 according to an embodiment of the invention;

[0095] Figure 15 illustrates a partial perspective view of an electric machine according to an embodiment of the invention;

[0096] Figure 16 illustrates a cross section view of a tube according to an embodiment of the invention;

[0097] Figure 17 illustrates a cross section view of a tube according to an embodiment of the invention;

[0098] Figure 18 illustrates a cross sectional image of an electric machine according to an embodiment of the invention with cooling passages through the stator;

[0099] Figure 19 illustrates a cross sectional image of an electric machine according to an embodiment of the invention with cooling passages through the stator and a central oil inlet;

[0100] Figure 20 illustrates a partial perspective view of an electric machine according to an embodiment of the invention;

[0101] Figure 21 illustrates a partial view of a stator forming part of an electric machine according to an embodiment of the invention;

[0102] Figure 22 illustrates a cross sectional view of material bridges of the stator according to an embodiment of the invention;

[0103] Figure 23 illustrates a partial cross sectional view of a stator forming part of an electric machine according to an embodiment of the invention;

[0104] Figure 24 illustrates a partial cross sectional view of the radially outer edge of a stator of an electric machine according to an embodiment of the invention; Figure 25 illustrates a cross sectional image of a stator of an electric machine according to an embodiment of the invention;

[0105] Figure 26 illustrates a magnified partial view of the stator of Figure 23 forming part of an electric machine according to an embodiment of the invention; and

[0106] Figure 27 illustrates a vehicle in accordance with an embodiment of the invention.

[0107] DETAILED DESCRIPTION

[0108] Examples of the present disclosure relate to an electric machine, which may form part of a larger motor arrangement including various control electronics. Such an electric machine may be of a synchronous type or an asynchronous type, for example a permanent magnet synchronous motor.

[0109] In particular, examples of the present invention relate to an electric machine comprising a rotor and a stator, where the rotor and the stator are located, at least in part, within a motor housing.

[0110] In some examples, the electric machine comprises a tube, manifold, or baffle, arrangement configured or arranged to segregate or isolate components of the stator from the rotor. The tube arrangement has an end abutting a first end of the motor housing and an end abutting a second end of the motor housing.

[0111] In some examples, the stator incorporates various cooling arrangements to provide for the passage of a cooling fluid, such as oil, through the stator to enable cooling of the stator and components of the stator, during operation of the electric machine.

[0112] Non-limiting examples will now be described with reference to accompanying Figures 1 to 27, where the figures illustrate an electric machine 10 and a vehicle 300.

[0113] As illustrated in the example arrangements illustrated in Figures 1 to 5, the electric machine 10 of the present invention comprises a stator 20 having a cylindrical inner channel 30 with a central stator axis 32, and a rotor 50 coaxially located within the cylindrical inner channel 30 of the stator 20. The central stator axis 32 is also a rotational axis about which the rotor 50 is arranged or configured to rotate. The rotor 50 and stator 20 are located, at least in part, within a motor housing 70. The rotor 50 is separated from the stator by a gap 68, often called an air gap or clearance gap. The gap 68 ensures unhindered mechanical rotation of the rotor relative to the stator and may affect performance parameters of the motor including efficiency, starting current, torque, and the temperature rise of the motor. Ideally the gap 68 should be constant along the length of the overlap of the rotor 50 and the stator 20. Ideally the gap 68 should be constant between the inner circumference of the static part of the motor and the outer circumference of the rotating part of the motor. In a motor with no intervening parts between the rotor 50 and the stator, the gap 68 should be constant around the external circumference of the rotor 50 between the external circumference of the rotor 50 and internal circumference stator 50, as this will avoid or minimise uneven magnetic interactions between the rotor 50 and stator 20, thereby minimising motor vibration and optimising the efficiency of the motor.

[0114] The rotor 50 has an outer surface concentric with the curved inner surface 34 of the stator 20, such that during rotation of the rotor 50 a consistent gap 68 is maintained between the rotor 50 and the stator 20. The rotor 50 and the stator 20 may each be constructed from a plurality of lamina or laminations, arranged or laminated to form a respective elongate rotor 50 and stator 20.

[0115] The stator 20 comprises a stator core which may be formed as a multi-part stator. For example, the stator 20 may be comprised of an inner stator 36 and an outer stator 38, such as the arrangements more clearly seen in Figure 8 and Figure 21 , though other arrangements of the stator 20, such as a single piece stator or a circumferentially segmented stator, may also be used in the present invention.

[0116] The cylindrical inner channel 30 has a curved inner surface 34 and a central stator axis 32. The central stator axis 32 is located parallel to the curved inner surface 34 of the cylindrical inner channel 30. The stator 20 comprises a plurality of winding slots 40, for the retention of electrical windings 42, through the stator 20. For example, the electric machine 10 may comprise forty eight slots and eight rotor poles. In another example, the electric machine 10 may comprise fifty four slots and six rotor poles. Other combinations of winding slot numbers and rotor pole numbers may be provided in other examples. Each of the plurality of winding slots 40 has a length extending along a respective radial axis 46 extending from, and orthogonal to, the central stator axis 32. Each of the plurality of winding slots 40 also extends along the full length of the stator 20, parallel to the central stator axis 32. In various embodiments, the electric machine 10 comprises a first tubular section 80 having a first end 82 and a second end 84. The first end 82 may be of circular cross section and the second end 84 may be of circular cross section. In various embodiments the first tubular section 80 may have a constant radius along its axial length, that is the length parallel to the central stator axis 32, though in alternative embodiments the first tubular section 80 may be frustoconical in shape or have a varying radius along its axial length.

[0117] When the electric machine 10 has been constructed from its constituent parts, the first end 82 of the first tubular section 80 is located at a first end 72 of the motor housing 70 and the second end 84 of the first tubular section 80 is located at a first end 22 of the stator 20.

[0118] The electric machine 10 comprises a second tubular section 180 having a first end 182 and a second end 184. The first end may be of circular cross section and the second end 184 may be of circular cross section. In various embodiments the second tubular section 180 may have a constant radius along its axial length, that is the length parallel to the central stator axis 32, though in alternative embodiments the second tubular section 180 may be frustoconical in shape or have a varying radius along its axial length.

[0119] When the electric machine 10 has been constructed from its constituent parts, the first end 182 of the second tubular section 180 is located at a second end 172 of the motor housing 70 and the second end 184 of the second tubular section 180 is located at a second end 122 of the stator 20.

[0120] In some embodiments, in particular as shown in Figures 1 to 5, the first tubular section 80 is identical to the second tubular section 180, though in other embodiments, in particular as shown in Figure 15, the first tubular section 80 may be of a different form, such as having a different inner and / or outer diameter than the second tubular section 180. An example of such an arrangement is described herein with respect to Figure 15.

[0121] In some examples, the second end 84 of the first tubular section 80 has an outer diameter substantially equal to the diameter of the cylindrical inner channel 30 of the stator 20 at the first end 22 of the stator and the second end 184 of the second tubular section 180 has an outer diameter substantially equal to the diameter of the cylindrical inner channel 30 of the stator at the second end 122 of the stator 20.

[0122] The second end 84 of the first tubular section 80 may be radially inboard of winding slots 40 at the first end 22 of the stator 20, and the second end 184 of the second tubular section 180 may be radially inboard of winding slots 40 at the second end 122 of the stator 120, the winding slots 40 being apertures through the stator 120 which house electrical windings 42 of the electrical machine 10.

[0123] The first tubular section 80 and second tubular section 180 are therefore located in respective positions whereby they will not interfere with the insertion of, or positioning of, electrical windings 42 into the winding slots 40. If the electric machine 10 is provided with electrical windings 42 prior to the locating of the first tubular section 80 and / or second tubular section 180, the insertion of or positioning of the first tubular section 80 and / or the second tubular section 180 is not detrimentally affected by the presence of the electrical windings 42.

[0124] By the first tubular section 80 and second tubular section 180 being radially inboard of the winding slots 40 through the stator 20, through which the electrical windings 42 are located, a cooling fluid, such as oil, which may be caused to flow through the winding slots 40 as part of an electric machine cooling arrangement, can be maintained away from the rotor 50 whilst directly cooling the electrical windings 42 within the winding slots 40.

[0125] The motor housing 70 may comprise a first bearing housing 74 at the first end 72 of the motor housing 70, against which the first end 82 of the first tubular section 80 is engaged. In some embodiments the first bearing housing 74 may not be circular in cross section, and it is to be understood that the first end 82 of the first tubular section 80 will have a form corresponding to that of the first bearing housing 74, such that, as will be described below, the first tubular section 80 may abut the first bearing housing 74 to provide a sealed engagement therebetween.

[0126] The first bearing housing 74 provides a first bearing surface 76 against which the first tubular section 80 may abut. The first bearing surface 76 may therefore be considered to be a first abutment surface or a first sealing surface against which the first tubular section 80 engages.

[0127] The stator 20, in particular the first end 22 of the stator 20, provides a surface against which the first tubular section 80 may abut. The first end 22 of the stator 20 may therefore be considered to be a second abutment surface or a second sealing surface against which the first tubular section 80 engages.

[0128] The first bearing surface 76 is a section of the first bearing housing 74 that extends axially, parallel with the central stator axis 32, and against which an inner surface 86 of the first end 82 of the first tubular section 80 is engaged. The first bearing surface 76 forming the axially extending section of the first bearing housing 74 may have a circular cross section such that the first end 82 of the first tubular section 80, which may also be circular in cross section, can be positioned over the first bearing surface 76 of the first bearing housing 74 to engage with the first bearing surface 76 of the first bearing housing 74 in a push fit arrangement, or an interference fit engagement.

[0129] In other embodiments the length of the first end 82 of the first tubular section 80 which overlaps the first bearing surface 76 of the first bearing housing 74 may engage with first bearing surface 76 of the first bearing housing 74 in a loose fit arrangement, then being affixed or sealed to the first bearing housing 74 via an adhesive and / or via a welded connection, each of which may assist in preventing or minimising the flow of the cooling fluid or medium onto the rotor 50.

[0130] The axially extending section 76 of the first bearing housing 74 may, in some embodiments, comprise one or a plurality of O-ring seal channels 78, around the circumference or perimeter of the axially extending section 76 of the first bearing housing 74. The, or each, O-ring seal channel 78, is arranged or configured to retain an O-ring 44, wherein the, or each, O-ring 44 is located between the axially extending section 76 of the first bearing housing 74 and the inner surface 86 of the first end 82 of the first tubular section 80. Such O-ring arrangements provide sealing to prevent a cooling fluid, such as oil, which may be caused to flow through the winding slots 40 of the stator 20 as part of an electric machine cooling arrangement, from contact with the rotor 50, whilst directly cooling the electrical windings 42 within the winding slots 40.

[0131] The motor housing 70 may also comprise a second bearing housing 174 at the second end 172 of the motor housing 70, against which the first end 182 of the second tubular section 180 is engaged.

[0132] The second bearing housing 174 provides a second bearing surface 176 against which the second tubular section 180 may abut. The second bearing surface 176 may therefore be considered to be a third abutment surface or a third sealing surface against which the second tubular section 180 engages.

[0133] The stator 20, in particular the second end 122 of the stator 20 provides a surface against which the second tubular section 180 may abut. The second end 122 of the stator 20 may therefore be considered to be a fourth abutment surface or a fourth sealing surface against which the second tubular section 180 engages.

[0134] The second bearing surface 176 is a section of the second bearing housing 174 that extends axially, parallel with the central stator axis 32, and against which an inner surface 186 of the first end 182 of the second tubular section 180 is engaged.

[0135] The second bearing surface 176 forming the axially extending section of the second bearing housing 174 may have a circular cross section such that the first end 182 of the second tubular section 180, which may also be circular in cross section, can be positioned over the second bearing surface 176 of the second bearing housing 174 to engage with the second bearing surface 176 of the second bearing housing 174 in a push fit arrangement, or an interference fit engagement.

[0136] In other embodiments the length of the first end 182 of the second tubular section 180 which overlaps the second bearing surface 176 of the second bearing housing 174 may engage with second bearing surface 176 of the second bearing housing 174 in a loose fit arrangement, then being affixed or sealed to the second bearing housing 174 via an adhesive and / or via a welded connection, each of which may assist in preventing or minimising the flow of the cooling fluid or medium onto the rotor 50.

[0137] The axially extending section 176 of the second bearing housing 174 may, in some embodiments, comprise one or a plurality of O-ring seal channels 178, around the circumference or perimeter of the axially extending section 176 of the second bearing housing 174. The, or each, O-ring seal channel 178, is arranged or configured to retain an O-ring 144, wherein the, or each, O-ring 144 is located between the axially extending section 176 of the second bearing housing 174 and the inner surface 186 of the first end 182 of the second tubular section 180. Such O-ring arrangements provide sealing to prevent a cooling fluid, such as oil, which may be caused to flow through the winding slots 40 of the stator 20 as part of an electric machine cooling arrangement, from contact with the rotor 50, whilst directly cooling the electrical windings 42 within the winding slots 40.

[0138] Figure 1 illustrates an arrangement of a first example electric machine 10 having a first tubular section 80 overlapping a first end 22 of the stator 20 along the central stator axis 32 in order to provide a physical segregation of the rotor 50 from a cooling arrangement of the electric machine 10, where the cooling arrangement is configured to provide a cooling fluid or medium, for example oil, to the stator 20 in such a way as to transport heat generated by the windings 42 in the winding slots 40 of the stator 20 away from the stator 20.

[0139] In the arrangement of Figure 1 , the first end 22 of the stator 20, proximal to the first tubular section 80, comprises a first stator section 24 and a second stator section 26, the first stator section 24 of the first end 22 of the stator 20 being closer than the second stator section 26 of the first end 22 of the stator 20 to a terminal end 28 of the first end 22 of the stator 20.

[0140] The first stator section 24 of the first end 22 of the stator 20 provides a section of stator 20 which has an increased diameter bore in the cylindrical inner channel 30 of the stator 20 relative to the second stator section 26 of the first end 22 of the stator 20. That is, the inner diameter of the stator 20 at or near the terminal end 28 at the first end 22 of the stator 20 is greater than the inner diameter of the stator 20 further away from the terminal end 28 at the first end 22 of the stator 20, thus providing an inner step or lip within the cylindrical inner channel 30.

[0141] In Figure 1 , the rotor 50 is of the same length as the stator 20 and overlaps the stator 20 along the central stator axis 32 such that the rotor 50 is positioned to be fully within the cylindrical inner channel 30 of the stator 20. In this arrangement the gap 68 between the rotor 50 and the stator 20 is greater at the first stator section 24 of the first end 22 of the stator 20 than the gap 68 between the rotor 50 and the stator 20 at the second stator section 26 of the first end 22 of the stator 20. The larger gap 68 at the first stator section 24 of the first end 22 of the stator 20 facilitates the insertion of a length of the second end 84 of the first tubular section 80. Once the length of the second end 84 of the first tubular section 80 is inserted between the rotor 50 and the stator 20, the gap 68 between the length of the second end 84 of the first tubular section 80 and the rotor 50 is equal to, or substantially equal to, the gap 68 between the second stator section 26 of the first end 22 of the stator 20 and the rotor 50.

[0142] The first stator section 24 of the first end 22 of the stator 20 is therefore arranged or configured to receive a length of the second end 84 of the first tubular section 80 to provide an overlap of the stator 20 and the first tubular section 80 parallel to the central stator axis 32. In Figure 1 , the thickness of the first tubular section 80 is equal to, or substantially equal to, the difference in the inner diameter of the stator 20 between the first stator section 24 of the first end 22 of the stator 20 and the second stator section 26 of the first end 22 of the stator 20. In other embodiments the thickness of the first tubular section 80 may be smaller than the difference in the inner diameter of the stator 20 between the first stator section 24 of the first end 22 of the stator 20 and the second stator section 26 of the first end 22 of the stator 20. In order to provide the different diameter bore sections of stator 20, the stator 20 may be formed from different lamination configurations, in the example shown there are two different lamination configurations. The plurality of stator laminations provided for the first stator section 24 of the first end 22 of the stator 20 each have a larger diameter central aperture than each of the plurality of stator laminations provided for the second stator section 26 of the first end 22 of the stator 20, thereby providing an increased diameter bore at the first stator section 24 of the first end 22 of the stator 20 over the second stator section 26 of the first end 22 of the stator 20.

[0143] In order to provide such an arrangement of a first stator section 24 of the first end 22 of the stator 20 and a second stator section 26 of the first end 22 of the stator 20, the first stator section 24 of the first end 22 of the stator 20 may be formed from differently stamped laminae or laminations than are used to form the second stator section 26 of the first end 22 of the stator 20. Each of the laminae of the first stator section 24 of the first end 22 of the stator 20 comprises a central aperture with a diameter which is greater than the diameter of a central aperture of each of the laminae of the second stator section 26 of the first end 22 of the stator 20.

[0144] In an alternative embodiment, the laminae or laminations for both the first stator section 24 of the first end 22 of the stator 20 and the second stator section 26 of the first end 22 of the stator 20 may be formed with the same diameter central aperture and, once the stator 20 has been constructed by joining each of the stator laminae together, the central aperture of the first stator section 24 of the first end 22 of the stator 20 may be machined to provide a larger diameter inner bore at the first stator section 24 of the first end 22 of the stator 20.

[0145] In another alternative embodiment, the laminae or laminations for both the first stator section 24 of the first end 22 of the stator 20 and the second stator section 26 of the first end 22 of the stator 20 may be formed without a central aperture and, once the stator 20 has been constructed by joining each of the stator laminae together, the central aperture of the second stator section 26 of the first end 22 of the stator 20, and optionally the first stator section 24 of the first end 22 of the stator 20, may be machined in a first machining operation to provide an inner bore of a first diameter and the first stator section 24 of the first end 22 of the stator 20 may be machined, or further machined, in a second machining operation to provide a larger diameter inner bore at the first stator section 24 of the first end 22 of the stator 20 than provided at the second stator section 26 of the first end 22 of the stator 20. In some embodiments the first and second machining operations may be provided by a single machining operation using a tool having a varying diameter cutting blade for cutting the inner bore of the stator 20.

[0146] Therefore, the cylindrical inner channel 30 of the stator 20 comprises a step with a larger bore diameter closer to the terminal end 28 of the first end 22 of the stator 20 and a smaller bore diameter further from the terminal end 28 of the first end 22 of the stator 20.

[0147] The length of the second end 84 of the first tubular section 80 which overlaps the stator 20 parallel to the central stator axis 32 engages with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a push fit engagement or an interference fit engagement. This provides a seal against which the flow of a cooling fluid or medium is resisted, thereby preventing or minimising the flow of the cooling fluid or medium onto the rotor 50.

[0148] In other embodiments the length of the second end 84 of the first tubular section 80 which overlaps the stator 20 parallel to the central stator axis 32 may engage with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a loose fit arrangement, then being affixed or sealed to the stator 20 via an adhesive and / or via a welded connection, each of which may assist in preventing or minimising the flow of the cooling fluid or medium onto the rotor 50.

[0149] In order to provide an improved seal between stator 20 and the rotor 50 to prevent or minimise the flow of the cooling fluid or medium onto the rotor 50, an axially placed seal 92 may be provided between a terminal end 90 of the second end 84 of the first tubular section 80 and the second stator section 26 of the first end 22 of the stator 20, in particular abutting the step or lip formed due to the difference in the bore diameter of the cylindrical inner channel 30 at the first stator section 24 of the first end 22 of the stator 20 and the bore diameter of the cylindrical inner channel 30 at the second stator section 26 of the first end 22 of the stator 20. The axially placed seal 92 may be an O-ring seal, a lip seal, or a gasket which is located between the first tubular section 80 and the second stator section 26 of the first end 22 of the stator 20.

[0150] It will be noted that in Figure 1 , the second end 122 of the stator 20 is a mirror image of the first end 22 of the stator. However, in other embodiments a different configuration, such as those shown in Figures 2 to 14 may be provided at the second end 122 of the stator 20. As shown in the embodiment of Figure 1 , the second end 122 of the stator 20, proximal to the second tubular section 180, comprises a first stator section 124 and a second stator section 126, the first stator section 124 of the second end 122 of the stator 20 being closer than the second stator section 126 of the second end 122 of the stator 20 to a terminal end 128 of the second end 122 of the stator 20.

[0151] The first stator section 124 of the second end 122 of the stator 20 provides a section of stator 20 which has an increased diameter bore in the cylindrical inner channel 30 of the stator 20 relative to the second stator section 126 of the second end 122 of the stator 20. That is, the inner diameter of the stator 20 at or near the terminal end 128 at the second end 122 of the stator 20 is greater than the inner diameter of the stator 20 further away from the terminal end 128 at the second end 122 of the stator 20, thus providing an inner step or lip within the cylindrical inner channel 30.

[0152] Such an arrangement provides a gap 68 between the rotor 50 and the stator 20 which is greater at the first stator section 124 of the second end 122 of the stator 20 than the gap 68 between the rotor 50 and the stator 20 at the second stator section 126 of the second end 122 of the stator 20. The larger gap 68 at the first stator section 124 of the second end 122 of the stator 20 facilitates the insertion of a length of the second end 184 of the second tubular section 180. Once the length of the second end 184 of the second tubular section 180 is inserted between the rotor 50 and the stator 20, the gap 68 between the length of the second end 184 of the second tubular section 180 and the rotor 50 is equal to, or substantially equal to, the gap 68 between the second stator section 126 of the second end 122 of the stator 20 and the rotor 50.

[0153] The first stator section 124 of the second end 122 of the stator 20 is therefore arranged or configured to receive a length of the second end 184 of the second tubular section 180 to provide an overlap of the stator 20 and the second tubular section 180 parallel to the central stator axis 32. In Figure 1 , the thickness of the second tubular section 180 is equal to, or substantially equal to, the difference in the inner diameter of the stator 20 between the first stator section 124 of the second end 122 of the stator 20 and the second stator section 126 of the second end 122 of the stator 20. In other embodiments the thickness of the second tubular section 180 may be smaller than the difference in the inner diameter of the stator 20 between the first stator section 124 of the second end 122 of the stator 20 and the second stator section 126 of the second end 122 of the stator 20. As noted above in relation to the first end 22 of the stator 20, in order to provide the different diameter bore sections of stator 20 at the second end 122 of the stator 20, the stator 20 may be formed from different lamination configurations. In the example shown in Figure 1 there are two different lamination configurations. The plurality of stator laminations provided for the first stator section 124 of the second end 122 of the stator 20 each have a larger diameter central aperture than each of the plurality of stator laminations provided for the second stator section 126 of the second end 122 of the stator 20, thereby providing an increased diameter bore at the first stator section 124 of the second end 22 of the stator 20 over the second stator section 126 of the second end 22 of the stator 20.

[0154] In order to provide such an arrangement of a first stator section 124 of the second end 122 of the stator 20 and a second stator section 126 of the second end 122 of the stator 20, the first stator section 124 of the second end 122 of the stator 20 may be formed from differently stamped laminae or laminations than are used to form the second stator section 126 of the second end 122 of the stator 20. Each of the laminae of the first stator section 124 of the second end 122 of the stator 20 comprises a central aperture with a diameter which is greater than the diameter of a central aperture of each of the laminae of the second stator section 126 of the second end 122 of the stator 20.

[0155] In an alternative embodiment, the laminae or laminations for both the first stator section 124 of the second end 122 of the stator 20 and the second stator section 126 of the second end 122 of the stator 20 may be formed with the same diameter central aperture and, once the stator 20 has been constructed by joining each of the stator laminae together, the central aperture of the first stator section 124 of the second end 122 of the stator 20 may be machined to provide a larger diameter inner bore at the first stator section 124 of the second end 122 of the stator 20.

[0156] In another alternative embodiment, the laminae or laminations for both the first stator section 124 of the second end 122 of the stator 20 and the second stator section 126 of the second end 122 of the stator 20 may be formed without a central aperture and, once the stator 20 has been constructed by joining each of the stator laminae together, the central aperture of the second stator section 126 of the second end 122 of the stator 20, and optionally the first stator section 124 of the second end 122 of the stator 20, may be machined in a first machining operation to provide an inner bore of a first diameter and the first stator section 124 of the second end 122 of the stator 20 may be machined, or further machined, in a second machining operation to provide a larger diameter inner bore at the first stator section 124 of the second end 122 of the stator 20 than provided at the second stator section 126 of the second end 122 of the stator 20.

[0157] In some embodiments the first and second machining operations may be provided by a single machining operation using a tool having a varying diameter cutting blade for cutting the inner bore of the stator 20.

[0158] Further, the machining steps for the first end 22 of the stator 20 and the second end 122 of the stator 20 may be combined, for example by machining the central aperture of the second stator section 26 of the first end 22 of the stator 20, the second stator section 126 of the second end 122 of the stator 20, the first stator section 24 of the first end 22 of the stator 20, and the first stator section 124 of the second end 122 of the stator, in a first machining operation, prior to additional machining operations on the first stator section 24 of the first end 22 of the stator 20 and the first stator section 124 of the second end 122 of the stator to provide larger diameter bores at the first stator section 24 of the first end 22 of the stator 20 and the first stator section 124 of the second end 122 of the stator.

[0159] Therefore, the cylindrical inner channel 30 of the stator 20 comprises a step with a larger bore diameter closer to the terminal end 128 of the second end 122 of the stator 20 and a smaller bore diameter further from the terminal end 128 of the second end 122 of the stator 20.

[0160] The length of the second end 184 of the second tubular section 180 which overlaps the stator 20 parallel to the central stator axis 32 engages with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a push fit engagement or an interference fit engagement. This provides a seal against which the flow of a cooling fluid or medium is resisted, thereby preventing or minimising the flow of the cooling fluid or medium onto the rotor 50. In other embodiments the length of the second end 184 of the second tubular section 180 which overlaps the stator 20 parallel to the central stator axis 32 may engage with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a loose fit arrangement, then being affixed or sealed to the stator 20 via an adhesive and / or via a welded connection, each of which may assist in preventing or minimising the flow of the cooling fluid or medium onto the rotor 50.

[0161] In order to provide an improved seal between stator 20 and the rotor 50 to prevent or minimise the flow of the cooling fluid or medium onto the rotor 50, an axially placed seal 192 may be provided between a terminal end 190 of the second end 184 of the second tubular section 180 and the second stator section 126 of the second end 122 of the stator 20, in particular abutting the step or lip formed due to the difference in the bore diameter of the cylindrical inner channel 30 at the first stator section 124 of the second end 122 of the stator 20 and the bore diameter of the cylindrical inner channel 30 at the second stator section 126 of the second end 122 of the stator 20. The axially placed seal 192 may be an O-ring seal, a lip seal, or a gasket which is located between the second tubular section 180 and the second stator section 126 of the second end 122 of the stator 20.

[0162] In alternative embodiments the step in the cylindrical inner channel 30 may be provided by a reduction in the diameter of the rotor 50, whilst maintaining the same bore diameter along the entire length of the stator 20.

[0163] As illustrated in Figures 2 to 4, the first end 22 of the stator 20, proximal to the first tubular section 80, comprises a first stator section 24 and a second stator section 26, the first stator section 24 of the first end 22 of the stator 20 being closer than the second stator section 26 of the first end 22 of the stator 20 to a terminal end 28 of the first end 22 of the stator 20.

[0164] The first stator section 24 of the first end 22 of the stator 20 and the second stator section 26 of the first end 22 of the stator 20 have the same bore diameter, therefore in order to facilitate the insertion of a length of the first tubular section 80 into the cylindrical inner channel 30, the rotor 50 may be of a modified form. In the arrangement of Figures 2 to 4 a first end 52 of the rotor 50, proximal to the first tubular section 80, comprises a first rotor section 56 and a second rotor section 54, the second rotor section 54 of the first end 52 of the rotor 50 being closer than the first rotor section 56 of the first end 52 of the rotor 50 to a terminal end 58 of the first end 52 of the rotor 50.

[0165] The second rotor section 54 of the first end 52 of the rotor 50 has a smaller diameter relative to the first rotor section 56 of the first end 52 of the rotor 50, thereby providing an increased gap into which the first tubular section 80 can be inserted whilst maintaining a separation between the first tubular section 80 and the rotor 50. The section of decreased diameter rotor provides a clearance gap 68 between the rotor 50 and the first tubular section 80 when the first tubular section 80 overlaps the stator 20 parallel to the central stator axis 32. In particular, the second rotor section 54 of the first end 52 of the rotor 50 is arranged or configured to allow an overlap of the first stator section 24 of the first end 22 of the stator 20 and the first tubular section 80 parallel to the central stator axis 32. The larger gap 68 at the second rotor section 54 of the first end 52 of the rotor 50 facilitates the insertion of a length of the second end 84 of the first tubular section 80. Once the length of the second end 84 of the first tubular section 80 is inserted between the rotor 50 and the stator 20, the gap 68 between the length of the second end 84 of the first tubular section 80 and the rotor 50 is equal to, or substantially equal to, the gap 68 between the second stator section 26 of the first end 22 of the stator 20 and the rotor 50.

[0166] In other words, the rotor 50, at the first end 52, comprises a step with a smaller diameter section being closer to the terminal end 58 of the first end 52 of the rotor 50 and a larger diameter section further from the terminal end 58 of the first end 52 of the rotor 50. This arrangement provides for a clearance gap 68 between the rotor 50 and the first tubular section 80 when the first tubular section 80 is arranged to overlap the stator 20 parallel to the central stator axis 32. The first stator section 24 of the first end 22 of the stator 20 can then receive a length of the second end 84 of the first tubular section 80 to provide an overlap of the stator 20 and the first tubular section 80 parallel to the central stator axis 32.

[0167] It will be noted that in Figures 2 to 4, the second end 122 of the stator 20 is a mirror image of the first end 22 of the stator 20. However, in other embodiments a different configuration may be provided at the second end 122 of the stator 20, including any of those illustrated in Figures 1 to 14.

[0168] The second end 122 of the stator 20, proximal to the second tubular section 180, comprises a first stator section 124 and a second stator section 126, the first stator section 124 of the second end 122 of the stator 20 being closer than the second stator section 126 of the second end 122 of the stator 20 to a terminal end 128 of the second end 122 of the stator 20.

[0169] The first stator section 124 of the second end 122 of the stator 120 and the second stator section 126 of the second end 122 of the stator 20 have the same bore diameter, therefore in order to facilitate the insertion of a length of the second tubular section 180 into the cylindrical inner channel 30, the rotor 50 may be of a modified form. In the arrangement of Figures 2 to 4 a second end 152 of the rotor 50, proximal to the second tubular section 180, comprises a first rotor section 156 and a second rotor section 154 , the second rotor section 154 of the second end 152 of the rotor 50 being closer than the first rotor section 156 of the second end 152 of the rotor 50 to a terminal end 158 of the second end 152 of the rotor 50.

[0170] The second rotor section 154 of the second end 152 of the rotor 50 has a smaller diameter relative to the first rotor section 156 of the second end 152 of the rotor 50, thereby providing an increased gap into which the second tubular section 180 can be inserted whilst maintaining a separation between the second tubular section 180 and the rotor 50. The section of decreased diameter rotor provides a clearance gap 68 between the rotor 50 and the second tubular section 180 when the second tubular section 180 overlaps the stator 20 parallel to the central stator axis 32. In particular, the second rotor section 154 of the second end 152 of the rotor 50 is arranged or configured to allow an overlap of the first stator section 124 of the second end 122 of the stator 20 and the second tubular section 180 parallel to the central stator axis 32. The larger gap 68 at the second rotor section 154 of the second end 152 of the rotor 50 facilitates the insertion of a length of the second end 184 of the second tubular section 180. Once the length of the second end 184 of the second tubular section 180 is inserted between the rotor 50 and the stator 20, the gap 68 between the length of the second end 184 of the second tubular section 180 and the rotor 50 is equal to, or substantially equal to, the gap 68 between the second stator section 126 of the second end 122 of the stator 20 and the rotor 50.

[0171] In other words, the rotor, at the second end 152, comprises a step with a smaller diameter section being closer to the terminal end 158 of the second end 152 of the rotor 50 and a larger diameter section further from the terminal end 158 of the second end 152 of the rotor 50. This arrangement provides for a clearance gap 68 between the rotor 50 and the second tubular section 180 when the second tubular section 180 is arranged to overlap the stator 20 parallel to the central stator axis 32. The first stator section 124 of the second end 122 of the stator 20 can then receive a length of the second end 184 of the second tubular section 180 to provide an overlap of the stator 20 and the second tubular section 180 parallel to the central stator axis 32.

[0172] In one embodiment, as shown in Figure 3, the length of the second end 84 of the first tubular section 80 which overlaps the stator 20 parallel to the central stator axis 32 engages with an inner surface 34 of the cylindrical inner channel 30 of the stator in a push fit engagement or an interference fit engagement. Also, in the mirror image arrangement shown in Figure 3, the length of the second end 184 of the second tubular section 180 which overlaps the stator 20 parallel to the central stator axis 32 engages with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a push fit engagement or an interference fit engagement.

[0173] In other embodiments, for example illustrated in Figures 2 and 4, the length of the second end 84 of the first tubular section 80 which overlaps the stator 20 parallel to the central stator axis 32 engages with one or more O-ring seals 98 positioned between the second end 84 of the first tubular section 80 and the inner surface 34 of the cylindrical inner channel 30 of the stator 20. The one or more O-ring seals 98 may be positioned in channels or grooves around the circumference of the first tubular section 80 which overlaps the stator 20 parallel to the central stator axis 32. The length of the second end 184 of the second tubular section 180 which overlaps the stator 20 parallel to the central stator axis 32 engages with one or more O-ring seals 198 positioned between the second end 184 of the second tubular section 180 and the inner surface 34 of the cylindrical inner channel 30 of the stator 20. The one or more O-ring seals 198 may be positioned in channels or grooves around the circumference of the second tubular section 180 which overlaps the stator 20 parallel to the central stator axis 32.

[0174] A further modification of the arrangement of the electric machine 10 is illustrated in Figure 2 where the first tubular section 80 comprises a first portion 94 of a first thickness and a second portion 96 of a second thickness. The second portion 96 of the first tubular section 80 comprises a length of the second end 84 of the first tubular section 80 which is arranged or configured to overlap the stator 20 parallel to the central stator axis 32.

[0175] The thickness of the first portion 94 of the first tubular section 80 is greater than the thickness of the second portion 96 of the first tubular section 80, such that the outer diameter of the first portion 94 of the first tubular section 80 is greater than the outer diameter of the second portion 96 of the first tubular section 80. In this arrangement, the first portion 94 of the first tubular section 80 provides a radially extending surface 100 configured to radially overlap and be substantially parallel to a radially extending surface at a terminal end 28 of the first end 22 of the stator 20. A seal, such as an O-ring, a lip seal, or a gasket, may then be provided between the radially extending surface 100 of the first portion 94 of the first tubular section 80 and the terminal end 28 of the first end 22 of the stator 20.

[0176] In the arrangement of Figure 2, where the second end 122 of the stator 20 is a mirror image of the first end 22 of the stator 20, the second tubular section 180 comprises a first portion 194 of a first thickness and a second portion 196 of a second thickness. The second portion 196 of the second tubular section 180 comprises a length of the second end 184 of the second tubular section 180 which is arranged or configured to overlap the stator 20 parallel to the central stator axis 32.

[0177] The thickness of the first portion 194 of the second tubular section 180 is greater than the thickness of the second portion 196 of the second tubular section 180, such that the outer diameter of the first portion 194 of the second tubular section 180 is greater than the outer diameter of the second portion 196 of the second tubular section 180. In this arrangement, the first portion 194 of the second tubular section 180 provides a radially extending surface 200 configured to radially overlap and be substantially parallel to a radially extending surface at a terminal end 128 of the second end 122 of the stator 20. A seal, such as an O-ring, a lip seal, or a gasket may then be provided between the radially extending surface 200 of the first portion 194 of the second tubular section 180 and the terminal end 128 of the second end 122 of the stator 20.

[0178] In arrangements where the rotor 50 comprises a first rotor section 56 of the first end 52 of the rotor 50 which is a different diameter to a second rotor section 54 of the first end 52 of the rotor 50, the first rotor section 56 and the second rotor section 54 may comprise different motor configurations. The first rotor section 56 of the first end 52 of the rotor 50 may have a higher reluctance torque than the second rotor section 54 of the first end 52 of the rotor 50. In one example, where the second rotor section 54 of the first end 52 of the rotor 50 is of a smaller diameter to the first rotor section 56 of the first end 52 of the rotor 50, the first rotor section 56 may comprise a high reluctance torque permanent magnet rotor and the second rotor section 54 may comprise a high magnet-excitation torque rotor, which provides a different rotor configuration to increase torque density for the section of rotor which has a larger air gap 68 to the stator 20. In some examples, the first rotor section 56 of the first end 52 of the rotor 50 comprises a multi-layer barrier structure that houses permanent magnet sections and exhibits reluctance torque in the range of 40% to 80%, and the second rotor section 54 of the first end 52 of the rotor 50 comprises larger magnet sections in a structure where reluctance torque is <20%. It will be understood that different arrangements of the first rotor section 56 and second rotor section 54 of the first end 52 of the rotor 50 may be provided to exhibit a variation in reluctance torque between the first rotor section 56 and second rotor section 54, whilst providing an increased gap, between the second rotor section 54 and the stator 20 into which the first tubular section 80 can be inserted whilst maintaining a separation between the first tubular section 80 and the rotor 50.

[0179] Similarly, where the rotor 50 comprises a first rotor section 156 of the second end 152 of the rotor 50 which is a different diameter to a second rotor section 154 of the second end 152 of the rotor 50, the first rotor section 156 of the second end 152 of the rotor 50 and the second rotor section 154 of the second end 152 of the rotor 20 may comprise different rotor configurations. The first rotor section 156 of the second end 152 of the rotor 50 may have a higher reluctance torque than the second rotor section 154 of the second end 152 of the rotor 50. In one example, where the second rotor section 154 of the second end 152 of the rotor 50 is of a smaller diameter to the first rotor section 156 of the second end 152 of the rotor 50, the first rotor section 156 may comprise a high reluctance torque permanent magnet rotor and the second rotor section 154 may comprise a high magnet-excitation torque rotor, which provides a different rotor configuration to increase torque density for the section of rotor which has a larger air gap 68 to the stator 20. In some examples, the first rotor section 156 of the second end 152 of the rotor 50 comprises a multi-layer barrier structure that houses permanent magnet sections and exhibits reluctance torque in the range of 40% to 80%, and the second rotor section 154 of the second end 152 of the rotor 50 comprises larger magnet sections in a structure where reluctance torque is <20%. It will be understood that different arrangements of the first rotor section 156 and second rotor section 154 of the second end 152 of the rotor 50 may be provided to exhibit a variation in reluctance torque between the first rotor section 156 and second rotor section 154, whilst providing an increased gap, between the second rotor section 54 of the second end 152 of the rotor 50 and the stator 20 into which the second tubular section 180 can be inserted whilst maintaining a separation between the second tubular section 180 and the rotor 50.

[0180] In another embodiment, illustrated in Figure 5, rather than having a rotor 50 with a first rotor section 56 of the first end 52 of the rotor 50 which is a different diameter to a second rotor section 54 of the first end 52 of the rotor 50, the first end 52 of the rotor 50 is shorter than the first end 22 of the stator 20 along the direction of the central stator axis 32 to allow an overlap of the stator 20 and the first tubular section 80 parallel to the central stator axis 32.

[0181] Whilst the first stator section 24 of the first end 22 of the stator 20 may still be configured to receive a length of the second end 84 of the first tubular section 80 to provide an overlap of the stator 20 and the first tubular section 80 parallel to the central stator axis 32, in such an arrangement, there is no overlap parallel to the central stator axis 32, that is in a radial direction at any point on the central stator axis 32, of the first tubular section 80 and the rotor 50. Thus, the terminal end 58 of the first end 52 of the rotor 50 does not overlap the first tubular section 80 along the central stator axis 32.

[0182] As noted in relation to other arrangements, the length of the second end 84 of the first tubular section 80 overlaps the stator 20 parallel to the central stator axis 32 and may engage with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a push fit engagement or an interference fit engagement, or be engaged with the inner surface 34 of the cylindrical inner channel 30 of the stator via one or more O-rings.

[0183] Figure 5, also illustrates an arrangement where the second end 152 of the rotor 50 is also shorter than the second end 122 of the stator 20 along the direction of the central stator axis 32 to allow an overlap of the stator 20 and the second tubular section 180 parallel to the central stator axis 32. Whilst the first stator section 124 of the second end 122 of the stator 20 may still be configured to receive a length of the second end 184 of the second tubular section 180 to provide an overlap of the stator 20 and the second tubular section 180 parallel to the central stator axis 32, in such an arrangement, there is no overlap parallel to the central stator axis 32, that is in a radial direction at any point on the central stator axis 32, of the second tubular section 180 and the rotor 50. Thus, the terminal end 158 of the second end 152 of the rotor 50 does not overlap the second tubular section 180 along the central stator axis 32.

[0184] As noted in relation to other arrangements, the length of the second end 184 of the second tubular section 180 overlaps the stator 20 parallel to the central stator axis 32 and may engage with an inner surface 34 of the cylindrical inner channel 30 of the stator 20 in a push fit engagement or an interference fit engagement, or be engaged with the inner surface 34 of the cylindrical inner channel 30 of the stator via one or more O-rings.

[0185] In various embodiments, the stator 20 has a chamfered section 23 of the cylindrical inner channel 30 at the terminal end 28 of the stator 20, as illustrated in Figure 6 for the first end 22 of the stator 20. That is, the inner diameter of the stator 20 may be configured or arranged to be larger at the terminal end 28 of the stator 20 when compared to a central section of the cylindrical inner channel 30 of the stator 20. The inner diameter of the stator 20 may be configured to taper from the terminal end 28 of the stator 20 to the central section of the cylindrical inner channel 30 of the stator 20. The taper may be linear.

[0186] The inner diameter of the stator 20 may be configured or arranged to be larger at the terminal end 28 of the stator 30 than the outer diameter of the first tubular section 80 such that there is a clearance gap between the inner diameter of the stator 20 and the outer diameter of the first tubular section 80 at the terminal end 28 of the stator 20, thereby improving, or easing the facilitation of, the location and insertion of the first tubular section 80 into the cylindrical inner channel 30 of the stator 20.

[0187] The terminal end 128 of the second end 122 of the stator 20 may be configured in the same manner as the above described terminal end 28 of the first end 22 of the stator 20.

[0188] In some embodiments, the first tubular section 80 may have a chamfered section 81 at the second end 84 of the first tubular section 80. The outer diameter of the second end 84 of the first tubular section 80 may be configured or arranged to taper or decrease towards a terminal end 87 of the second end 84 of the first tubular section 80. The taper may be linear. The outer diameter of the first tubular section 80 may be configured or arranged to be smaller, at the terminal end 87 of the second end 84 of the first tubular section 80, than the inner diameter of the cylindrical inner channel 30 of the stator 20 at the terminal end 28 of the stator 20. In such an arrangement, there may be a clearance gap between the outer diameter of the first tubular section 80, at the terminal end 87 of the second end 84 of the first tubular section 80, and the inner diameter of the stator at the terminal end 28 of the stator 20, thereby improving, or easing the facilitation of, the location and insertion of the first tubular section 80 into the cylindrical inner channel 30 of the stator 20.

[0189] A terminal end 187 of the second end 184 of the second tubular section 180 may be configured in the same manner as the above described terminal end 87 of the second end 184 of the first tubular section 80.

[0190] Figure 6 also illustrates the use of O-ring seals 98 between the first tubular section 80 and the stator 20. In particular, Figure 6 illustrates two grooves or channels 99 in the second end 84 of the first tubular section 80 which are configured or arranged to receive and retain respective O-ring seals 98. In other embodiments, such grooves or channels 99 and associated O-rings may be omitted, in particular where the first tubular section 80 is in an interference fit with the stator 20. In other embodiments a single groove or channel, or a different number of grooves or channels, may be provided to receive and retain respective O-ring seals 98. In order to facilitate the positioning of such grooves or channels 99 in the second end 84 of the first tubular section 80, the second end 84 may be of a greater thickness than a central portion of the first tubular section 80, though in other embodiments the thickness of the first tubular section 80 may be substantially uniform along the length of the first tubular section 80, excepting the thickness at the grooves or channels 99 themselves.

[0191] The second end 184 of the second tubular section 180 may be configured as noted above in relation to the second end 84 of the first tubular section 180. In particular, the second end 184 of the second tubular section 180 may be configured with one or more grooves or channels to receive and retain respective O-ring seals, as described above in relation to the second end 84 of the first tubular section 80.

[0192] Figure 6 also illustrates an optional modification to the first end 82 of the first tubular section 80, where a chamfered section 83 is provided. The inner diameter of the first end 82 of the first tubular section 80 may be configured or arranged to increase towards the terminal end 89 of the first end 82 of the first tubular section 80. That is, the inner diameter of the first end 82 of the first tubular section 80 may taper from the terminal end 89 of the first end 82 of the first tubular section 80 along a length of the first tubular section 80. The taper may be linear.

[0193] The inner diameter of the first tubular section 80 may be configured or arranged to be larger, at the terminal end 89 of the first end 82 of the first tubular section 80, than the outer diameter of the first bearing housing 74. In such an arrangement, there is a clearance gap between the inner diameter of the first tubular section 80 and the outer diameter of the first bearing housing 74, thereby improving, or easing the facilitation of, the location and insertion of the first tubular section 80 over the first bearing housing 74. Figure 6 also illustrates an optional stop 85 which delimits the insertion of the first bearing housing 74 into the first tubular section 80.

[0194] The first end 182 of the second tubular section 180 may be configured as described above in relation to the first end 82 of the first tubular section 80.

[0195] Figure 7 illustrates an additional or alternative arrangement for improving, or easing the facilitation of, the location and insertion of a first tubular section 80 into the cylindrical inner channel 30 of the stator 20.

[0196] In Figure 7 a guide 75 may be provided on the terminal end 28 of the stator 20, which is configured to assist in the insertion of the first tubular section 80 into the cylindrical inner channel 30 of the stator 20. Where the first tubular section 80 comprises O-ring seals, the guide 75 may assist in the insertion of the first tubular section 80 into the cylindrical inner channel 30 of the stator 20 without damage to the O-rings.

[0197] The guide 75 may have a chamfered section 77 tapering towards the cylindrical inner channel 30 of the stator 20, therefore acting to guide the first tubular section 80 to be coaxial with the stator 20, when the first tubular section 80 is moved to be located within the cylindrical inner channel 30 of the stator 20.

[0198] The guide 75 may be located on the terminal end 28 of a stator 20 with no chamfered section, as illustrated in Figure 7, or may be located concentric with a chamfered section 23 of a chamfered stator, as illustrated in, and described above in relation to, Figure 6.

[0199] The guide 75 may be formed of glass fibre, polyphenylene sulfide (PPS), nylon 66 (PA66), a PPS and PA66 alloy or compound resin, or some other material with similar heat withstanding properties. The guide 75 may be affixed or adhered to the terminal end 28 of the first end 22 of the stator 20 using epoxy glue or resin.

[0200] In another embodiment, illustrated in Figure 8, the second end 84 of the first tubular section 80 may be affixed or adhered to the first end 22 of the stator 20, in particular to the terminal end 28 of the first end 22 of the stator 20. Such adherence may be provided by bonding or welding the first tubular section 80 to the stator 20, and for this purpose friction welding or laser welding may be used. The first tubular section 80 may be affixed or adhered to the first end 22 of the stator 20 at a location radially inward of the winding slots 40 so as to ensure that there is no interference with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. In some variations the axially outer lamination of the stator 20 at the first end 22 of the stator 20, that is the end lamination, has a smaller inner diameter in order to provide a surface on which to affix or adhere the second end 84 of the first tubular section 80. Adherence of the first tubular section 80 to the first end 22 of the stator 20, by bonding, welding or otherwise, may assist in providing a fluidic seal to prevent cooling fluid or medium from passing through and on to the rotor 50.

[0201] Similarly, in embodiments of the invention where the arrangement at both sides of the stator 20 is mirrored, or substantially mirrored, the second end 184 of the second tubular section 180 may be affixed or adhered to the second end 122 of the stator 20, in particular to the terminal end 128 of the second end 122 of the stator 20. Such adherence may be provided by bonding or welding the second tubular section 180 to the stator 20, and for this purpose friction welding or laser welding may be used. The second tubular section 180 may be affixed or adhered to the second end 122 of the stator 20 at a location radially inward of the winding slots 40 so as to ensure that there is no interference with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. In some variations the axially outer lamination of the stator 20 at the second end 122 of the stator 20, that is the end lamination, has a smaller inner diameter in order to provide a surface on which to affix or adhere the second end 184 of the second tubular section 180. Adherence of the second tubular section 180 to the second end 122 of the stator 20, by bonding, welding or otherwise, may assist in providing a fluidic seal to prevent cooling fluid or medium from passing through and on to the rotor 50.

[0202] In another embodiment, illustrated in Figure 9, Figure 10, and Figure 11 , the first tubular section 80 comprises two components, a tube or sleeve 310 and a mask or toothed disc 320. The sleeve 310 and the toothed disc 320 may be formed together, or formed as separate components that are then joined or abutted to form a shield or tubular section 80 to deflect cooling fluid, such as oil, away from the rotor 50. The sleeve 310 may be overmoulded onto the toothed disc 320.

[0203] Figures 9, 10, and 11 illustrate one particular embodiment of a first tubular section 80 which may be formed by overmoulding a sleeve 310 to a toothed disc 320 or by otherwise adhering the sleeve 310 to the toothed disc 320. Figure 9 illustrates a perspective view of the first end 22 of the stator 20 with a first tubular section 80 located at the terminal end 28 of the first end 22 of the stator 20. Figure 10 illustrates a cross sectional view of the first end 22 of the stator, parallel to a central stator axis 32, with the first tubular section 80 located at the terminal end 28 of the first end 22 of the stator 20. Figure 11 illustrates an end view of the first end 22 of the stator 20 with the first tubular section 80 located at the terminal end 28 of the first end 22 of the stator 20.

[0204] The first end 82 of the first tubular section 80 is located at a first end 72 of the motor housing 70. The second end 84 of the first tubular section 80 may be affixed or adhered to the first end 22 of the stator 20, in particular to the terminal end 28 of the first end 22 of the stator 20. Such adherence may be provided by bonding or welding the first tubular section 80 to the stator 20, and for this purpose an epoxy glue or resin, friction welding or laser welding may be used, for example.

[0205] The toothed disc 320 may be located at the second end 84 of the first tubular section 80, such that the toothed disc 320 is the component of the first tubular section 80 that is affixed or adhered to the first end 22 of the stator 20, in particular to the terminal end 28 of the first end 22 of the stator 20. The toothed disc 320 may be affixed or adhered to the terminal end 28 of the first end 22 of the stator 20 using epoxy glue or resin. The toothed disc 320 may be formed of a polymer material, for example by a polymer moulding process.

[0206] When the first tubular section 80 is affixed or adhered to the first end 22 of the stator 20, the sleeve 310 may be positioned at a location radially inward of the winding slots 40 so as to ensure that there is no interference with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40.

[0207] A first portion 324 of the toothed disc 320 may also be positioned at a location radially inward of the winding slots 40 when the first tubular section 80 is affixed or adhered to the first end 22 of the stator 20 so as to ensure that there is no interference, by the first portion 324, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. The first portion 324 of the toothed disc 320 may be arranged or configured to be connected or affixed to the sleeve 310. In an embodiment, the first portion 324 of the toothed disc 320 comprises a circumferential channel or groove 322 for receiving a corresponding circumferential flange or lip 312 on the edge of the sleeve 310. An adhesive may be used to connect the groove 322 of the toothed disc 320 to the lip 312 of the sleeve 310, or the toothed disc 320 may be overmoulded onto the sleeve 310 to form a single part first tubular section 80, without the need to subsequently bond the two components together.

[0208] A plurality of second portions 326 of the toothed disc 320, forming a number, or plurality, of teeth 326, are affixed or adhered to the first end 22 of the stator 20 overlapping respective teeth 214 of the stator 20, so as to ensure that there is no interference, by the second portions 326, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. The second portions 326 of the toothed disc 320 may be affixed or adhered to the terminal end 28 of the first end 22 of the stator 20 using epoxy glue or resin. In particular, the second portions 326 of the toothed disc 320 may be affixed or adhered to respective teeth 214 of the stator at the first end 22 of the stator 20 using epoxy glue or resin.

[0209] A plurality of third portions 328 of the toothed disc 320, comprising a number of formations 328, may be affixed or adhered to the first end 22 of the stator 20, overlapping with corresponding steps 340 or other formations within the slot 40 of the stator 20. These third portions 328 of the toothed disc 320 may follow the shape of the corresponding steps 340 or be otherwise shaped to not overlap the slots 40 of the stator, so as to ensure that there is no interference, by the third portions 328, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. The third portions 328 of the toothed disc 320 may be affixed or adhered to the corresponding steps 340 or other formations within the slot 40 of the stator 20 using epoxy glue or resin.

[0210] Adherence of the first tubular section 80 to the first end 22 of the stator 20, by bonding, welding or otherwise, may assist in providing a fluidic seal to prevent cooling fluid or medium from passing through and on to the rotor 50.

[0211] Similarly, in embodiments of the invention where the arrangement at both sides of the stator 20 is mirrored, or substantially mirrored, the second tubular section 180 comprises two components, a tube or sleeve 310 and a mask or toothed disc 320. The sleeve 310 and the toothed disc 320 may be formed together, or formed as separate components that are then joined or abutted to form a shield or tubular section 80 to deflect cooling fluid, such as oil, away from the rotor 50. The sleeve 310 may be overmoulded onto the toothed disc 320.

[0212] The second end 184 of the second tubular section 180 may be affixed or adhered to the second end 122 of the stator 20, in particular to the terminal end 128 of the second end 122 of the stator 20. Such adherence may be provided by bonding or welding the second tubular section 180 to the stator 20, and for this purpose epoxy glue or resin, friction welding or laser welding may be used, for example.

[0213] The toothed disc 320 may be located at the second end 184 of the second tubular section 180, such that the toothed disc 320 is the component of the second tubular section 80 that is affixed or adhered to the second end 122 of the stator 20, in particular to the terminal end 128 of the second end 122 of the stator 20. The toothed disc 320 may be affixed or adhered to the terminal end 128 of the second end 122 of the stator 20 using epoxy glue or resin. The toothed disc 320 may be formed of a polymer material, for example by a polymer moulding process.

[0214] When the second tubular section 180 is affixed or adhered to the second end 122 of the stator 20, the sleeve 310 may be positioned at a location radially inward of the winding slots 40 so as to ensure that there is no interference with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40.

[0215] A first portion 324 of the toothed disc 320 may also be positioned at a location radially inward of the winding slots 40 when the second tubular section 180 is affixed or adhered to the second end 122 of the stator 20 so as to ensure that there is no interference, by the first portion 324, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40.

[0216] The first portion 324 of the toothed disc 320 may be arranged or configured to be connected or affixed to the sleeve 310. In an embodiment, the first portion 324 of the toothed disc 320 comprises a circumferential channel or groove 322 for receiving a corresponding circumferential flange or lip 312 on the edge of the sleeve 310. An adhesive may be used to connect the groove 322 of the toothed disc 320 to the lip 312 of the sleeve 310, or the toothed disc 320 may be overmoulded onto the sleeve 310 to form a single part first tubular section 80, without the need to subsequently bond the two components together.

[0217] A plurality of second portions 326 of the toothed disc 320, comprising a number of teeth 326, are affixed or adhered to the second end 122 of the stator 20 overlapping respective teeth 214 of the stator 20, so as to ensure that there is no interference, by the second portions 326, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. The second portions 326 of the toothed disc 320 may be affixed or adhered to the terminal end 128 of the second end 122 of the stator 20 using epoxy glue or resin. In particular, the second portions 326 of the toothed disc 320 may be affixed or adhered to respective teeth 214 of the stator at the second end 122 of the stator 20 using epoxy glue or resin.

[0218] A plurality of third portions 328 of the toothed disc 320, comprising a number of formations 328, may be affixed or adhered to the second end 122 of the stator 20, overlapping with corresponding steps 340 or other formations within the slot 40 of the stator 20. These third portions 328 of the toothed disc 320 may follow the shape of the corresponding steps 340 or be otherwise shaped to not overlap the slots 40 of the stator, so as to ensure that there is no interference, by the third portions 328, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. The third portions 328 of the toothed disc 320 may be affixed or adhered to the corresponding steps 340 or other formations within the slot 40 of the stator 20 using epoxy glue or resin.

[0219] Adherence of the second tubular section 180 to the second end 122 of the stator 20, by bonding, welding or otherwise, may assist in providing a fluidic seal to prevent cooling fluid or medium from passing through and on to the rotor 50.

[0220] In various alternative embodiments of the first tubular section 80, a sleeve 410 may be joined to a mask or toothed disc 420 via a clearance fit with a sealing arrangement such as an O- ring seal, an interference fit arrangement, by overmoulding the mask or toothed disc 420 onto the sleeve 410 or vice versa, or by otherwise adhering the sleeve 410 to the mask or toothed disc 420.

[0221] Figures 12, 13, and 14 illustrate an embodiment of a first tubular section 80 which may be formed by joining a sleeve 410 to a mask or toothed disc 420 using a clearance fit arrangement with an O-ring seal. An O-ring (not shown) can be placed in a groove or channel 412 in the sleeve 410, over which the mask or toothed disc 420 is positioned. In some embodiments, the sleeve 410 may have a chamfered leading edge 414 for ease of insertion onto the mask or toothed disc 420. The mask or toothed disc 420 may have a chamfered leading edge 422 for ease of insertion onto the sleeve 410 and prevention of damage to the O-ring in the channel 412. In other embodiments, which are modifications of the arrangement shown in Figures 11 , 12, and 13, the sleeve 410 may be joined to the mask or toothed disc 420 via other methods, such as via an interference fit arrangement, by overmoulding the mask or toothed disc 420 onto the sleeve 410, or by otherwise adhering the sleeve 410 to the mask or toothed disc 420.

[0222] In some arrangements, such as the arrangement shown in Figures 12, 13, and 14, the mask or toothed disc 420 is formed as a labyrinth mask 420, which provides a passage therethrough. In particular, the labyrinth mask 420 may provide a route, or path, for the passage of a cooling fluid, such as oil, from a location radially outward of the sleeve 410 to the winding slots 40 in the stator 20 and / or the passage of a cooling fluid, such as oil, from the winding slots 40 in the stator 20 to a location radially outward of the sleeve 410.

[0223] The labyrinth mask 420 may be non-magnetic and non-conducting and formed of a material suitable for withstanding high coolant or oil temperatures. For example, the labyrinth mask 420 may be formed of glass fibre, polyphenylene sulfide (PPS), nylon 66 (PA66), a PPS and PA66 alloy or compound resin, or some other material with similar heat withstanding properties.

[0224] Figure 12 illustrates the arrangement with electrical windings 42 illustrated in the winding slots 40 to illustrate the positioning of the electrical windings 42 relative to the components of the first tubular section 80. The labyrinth mask 420 comprises a first portion 424 connected to the sleeve 410 and a plurality of second portions 426 forming a number, or plurality, of teeth 426, which are affixed or adhered to the first end 22 of the stator 20, overlapping respective teeth 214 of the stator 20, so as to ensure that there is no interference, by the second portions 426, with the electrical windings 42 and / or the flow of cooling fluid or medium passing through the winding slots 40. The second portions 426 of the labyrinth mask 420 may be affixed or adhered to the terminal end 28 of the first end 22 of the stator 20 using epoxy glue or resin. In particular, the second portions 426 of the labyrinth mask 420 may be affixed or adhered to respective teeth 214 of the stator at the first end 22 of the stator 20 using epoxy glue or resin.

[0225] Figure 13, illustrated without the electrical windings 42 for clarity, shows a path for a cooling fluid, such as oil, through the labyrinth mask 420. The first part of the path 441 illustrates a that cooling fluid located radially outward of the sleeve 410 can flow into the labyrinth mask 420 to then pass through the labyrinth mask 420.

[0226] The cooling fluid passes, along the first part of the path 441 , through an aperture 428 in the labyrinth mask 420 and along a passage 430 into a chamber or plenum 432 which expands radially inwards from the passage 430 where the cooling fluid will follow a second part of the path 442. The chamber or plenum 432 expands circumferentially at its radially inner portion, as is more clearly shown from the view in Figure 14, to form a part 434 of the chamber or plenum 432 which is located at the radially inner portion of a winding slot 40 in the stator 20.

[0227] The cooling fluid will then follow a third part of the path 443 in a circumferential direction to the entry point to the winding slot 40 in the stator 20. The cooling fluid then follows a fourth part of the path 444 through the winding slot 40, from the first end 22 of the stator 20 towards the second end 122 of the stator 20.

[0228] Of course, it will be understood that the flow of cooling fluid may be reversed in some embodiments, depending on where the cooling fluid inlet, or oil inlet, and cooling fluid outlet, or oil outlet, are located. For example, the flow of cooling fluid, or oil, may be dependent upon which side of the stator 20 comprises a cooling fluid inlet, or oil inlet, and which side of the stator 20 comprises a cooling fluid outlet, or oil outlet.

[0229] Similarly, in embodiments of the invention where the arrangement at both sides of the stator 20 is mirrored, or substantially mirrored, the second tubular section 180 comprises two components, a tube or sleeve 410 and a mask or toothed disc 420, which may be in the form of the previously described labyrinth mask 420. The sleeve 410 and the mask or toothed disc 420 may be formed together, or formed as separate components that are then joined or abutted to form a shield or tubular section 80 to deflect cooling fluid, such as oil, away from the rotor 50. The sleeve 410 may be joined to the mask or toothed disc 420 using a clearance fit arrangement with an O-ring seal, as described above for the first tubular section 80 or the sleeve 410 may be joined to the mask or toothed disc 420 via other methods, such as via an interference fit arrangement, by overmoulding the mask or toothed disc 420 onto the sleeve 410, or by otherwise adhering the sleeve 410 to the mask or toothed disc 420.

[0230] In some embodiments of the invention as illustrated in Figure 15, Figure 16, and Figure 17, the first tubular section 80 and the second tubular section 180 are not separate but are connected or joined together via a third tubular section 280. The first tubular section 80, second tubular section 180 and third tubular section 280 may form a single tube, having been extruded, injection moulded, or otherwise formed as a continuous or homogeneous tubular section. The third tubular section 280 extends, along the length of the stator 20 parallel to the central stator axis 32, from the first tubular section 80 to the second tubular section 180, thereby extending from first end 22 of the stator 20 to the second end 122 of the stator 20. As illustrated in Figure 15, the third tubular section 280 may have a thickness less than the thickness of the first tubular section 80 and less than the thickness of the second tubular section 180. The thin third tubular section 280 can maintain a seal against the ingress of a cooling fluid or medium onto the rotor 50 and limit the effects on the electromagnetic properties of the electric machine 10, whilst the thicker first tubular section 80 and second tubular section 180 provide strength to the tubular arrangement.

[0231] The tubular arrangement is formed to allow the insertion of the first tubular section 80 through the stator 20 and the insertion of the rotor 50 through the second tubular section 180 to reside at the location of the third tubular section 280. In particular, the first tubular section 80 may have an inner diameter smaller than the inner diameter of the second tubular section 180 and the third tubular section 280, the inner diameter of the second tubular section 180 being equal to the inner diameter of the third tubular section 280. The outer diameter of the second tubular section 180 may be larger than the outer diameter of the first tubular section 80 and the third tubular section 280, the outer diameter of the first tubular section 80 being equal to the outer diameter of the third tubular section 280. This allows for the insertion of the rotor 50 into the second end 122 of the stator 20 without requiring an adjustable mandrel, whilst maintaining both strength of the first tubular section 80 and second tubular section 180 for ensuring good sealing to the motor housing 70 for the purposes of deflecting cooling fluid, such as oil, away from the rotor 50, and reducing the effects on the electromagnetic properties of the electric machine 10.

[0232] Whilst Figure 15 illustrates a first tubular section 80 and second tubular section 180 having respective inner walls 88 and 188 which are parallel with the central stator axis 32 and with each other, Figure 16 illustrates an alternative for this arrangement that may be provided in other embodiments. Figure 16 illustrates, in solid line, the inner wall 88 of the first tubular section 80 and the inner wall 188 of the second tubular section 180 being parallel with the central stator axis 32 and with each other, and in dashed line, the inner wall 88 of the first tubular section 80 and the inner wall 188 of the second tubular section 180 being tapered inwards towards the third tubular section 280. In various embodiments, the first tubular section 80 may have such a tapered inner wall 88, the second tubular section 180 may have such a tapered inner wall 188, or both the first tubular section 80 and the second tubular section 180 may have respective tapered inner walls 88, 188.

[0233] In an alternative arrangement illustrated in Figure 17, the first tubular section 80, second tubular section 180 and third tubular section 280 do not share common inner diameters or outer diameters, and may therefore provide steps on the inner surface and outer surface of the tube at the intersection of the first tubular section 80 and the third tubular section 280 and the intersection of the second tubular section 180 and the third tubular section 280. In such arrangements, the third tubular section 280 in which the rotor 50 resides, in use, comprises a thinner walled section, than either of the first tubular section 80 or second tubular section 180, in order to minimise the effects on the electromagnetic properties of the electric machine 10. A thicker wall may be maintained for the first tubular section 80 and / or second tubular section 180 in order to provide structural strength for engagement with the motor housing 70 to provide sealing against the passage of cooling fluid, such as oil, onto the rotor 50.

[0234] The purpose of the various arrangements of first tubular sections 80, second tubular sections 180 and third tubular sections 280 described above is to provide a sealed arrangement for the passage of oil, or other cooling fluid, through the stator 20, and preventing oil, or other cooling fluid, from impinging on the rotor 50.

[0235] As seen in Figure 8, Figure 9, Figure 20 and Figure 21 the stator 20 comprises winding slots 40, which extend parallel to the central stator axis 32, for retaining electrical windings 42.

[0236] As seen in Figure 17, within the winding slots 40 apertures 62, 64 may be provided between the electrical windings 42 and the winding slots 40 allowing oil, or a similar cooling medium, to pass through the winding slots 40 from an oil inlet to an oil outlet. Within the winding slots 40 there may be radially inner apertures 62 and radially outer apertures 64.

[0237] The radially inner apertures 62 may be formed by having a material bridge or bridge 350 of the winding slot 40 having a non-linear form such that the electrical windings 42 are positioned on a radially outer step 332 of the bridge of the winding slot 40, providing the radially inner aperture 62 radially inward of the radially outer step 332.

[0238] Figure 22 illustrates one form of bridge which may be used in some embodiments. In this embodiment, each asymmetric material bridge 350 comprises a first portion 330 comprising a first surface 332 inside the winding slot 40 and a second portion 334 comprising a second surface 336 inside the winding slot 40. In Figure 22 it is observed that, between two adjacent teeth 214-1, 214-2, a first portion 330 comprising a first surface 332 inside the winding slot 40 extends from the first one of the teeth 214-1 towards the second one of the teeth 214-2, and a second portion 334 comprising a second surface 336 inside the winding slot 40 extends from the second one of the teeth 214-2 towards the first one of the teeth 214-1 , wherein the first surface 332 is radially separated from the second surface 336. The first surface 332 is more radially distal from the central stator axis 32 of the stator 20 than the second surface 336, such that the thickness of the material bridge 350 at the first surface 332 is larger than the thickness of the material bridge at the second surface 336. The first surface 332 is on a plane or a curved plane parallel to the plane or curved plane of the second surface 336.

[0239] The first surface 332 can be seen to be a radially outer step or upper step upon which the radially inner one of the windings 42 in the slot 40 can be positioned. The second surface 336 can be seen to be a radially inner step or lower step which does not contact the radially inner one of the windings 42 in the slot 40, thereby creating a gap or radially inner aperture 62 which may be used as a cooling channel for cooling the windings 42. The radially inner aperture 62 forming the cooling channel may form part of a fluidic cooling system, whereby a cooling fluid or coolant, such as water or oil, can be passed through the radially inner aperture 62 in order to transfer heat from the windings 42, and the surrounding stator 20, to the cooling fluid or coolant.

[0240] Each asymmetric material bridge 350 comprises a third portion 338 extending from the first portion 330 to the second portion 334. The third portion 338 comprises a third surface 339 between the first surface 332 and the second surface 336.

[0241] The third surface 339 comprises a first curved section 342 extending from an end of the first surface 332, the end of the first surface 332 being the end furthest from the wall of the winding slot 40, that is, closest to the centreline 346 of the slot 40. The first curved section 342 curves towards the second surface 334, having an arc which deviates the plane of the third surface 339 greater than ninety degrees from the plane of the first surface 332.

[0242] The third surface 339 comprises a second curved section 344 extending from an end of the first curved section 342, the end of the first curved section 342 being the end furthest from the end of the first surface 332. The second curved section 344 curves towards, and terminates at, the second surface 334, the second curved section 344 having an arc which deviates the plane of the third surface 339 greater than ninety degrees.

[0243] In some embodiments the third surface 339 may comprise a straight section between the first curved section 342 and the second curved section 344.

[0244] The third surface 339 is configured such that at least a portion of the second curved section 344 overlaps one or more of the first surface 332 and the first curved section 342 along an axis parallel to the first surface 332. In some embodiments, at least a portion of the first curved section 342 may overlap the second curved section 344. In some embodiments, at least a portion of the first surface 332 may overlap a portion of the second surface 336.

[0245] In one example, the third surface 339 comprises a first curved section 342 having a circular arc with a radius of 0.25 mm, and a second curved section 344 having a circular arc with a radius of 0.25 mm, with no straight section therebetween, resulting in a first surface 332 which is 1 mm more radially distal from the central stator axis 32 of the stator 20 than the second surface 336.

[0246] The radially outer apertures 64 may be formed by having a separation between the radially outer surface of the electrical windings 42 and the outer surface of the winding slot 40. Where the stator 20 is formed with an inner stator 36 component and an outer stator 38 component, as illustrated for example in Figure 4 and Figure 5, a radially outer aperture 64 may be formed, at least in part, by a concavity 48 in the outer stator 38, where the concavity 48 is configured to be positioned above the winding slot 40 in the inner stator 36 when the outer stator 38 is fitted onto the inner stator 36. Figure 21 illustrates such a concavity 48 in the outer stator 38. During manufacture of the outer stator 38, this concavity 48 can be machined or stamped to provide a radially outer aperture 64 of sufficient size to enable appropriate transfer of heat from the windings 42, and the surrounding stator 20, to the cooling fluid or coolant passing therethrough for the application of the electric machine 10.

[0247] In some embodiments, the stator 20 additionally comprises a plurality of cooling ducts 66 through the stator 20, as illustrated in Figure 21 , Figure 23, Figure 24, and Figure 25. Each of the plurality of cooling ducts 66 extends parallel or substantially parallel to the central stator axis 32, from the terminal end 28 of the first end 22 of the stator 20 to the terminal end 128 of the second end 122 of the stator 20.

[0248] In some embodiments, as illustrated in Figure 21 and Figure 23, the cooling ducts 66 may be circular in cross section. In other embodiments, as illustrated in Figure 24, the cooling ducts 66 may be an approximate quadrilateral in cross section, such as rectangular or square, though it will be understood that other shapes of cooling ducts 66 may also be provided, such as triangular or oval shaped cross section cooling ducts.

[0249] Further illustrated in Figure 24 are open sections of the outer surface 288 of the stator 20, formed as channels 67 along the stator 20 parallel to the central stator axis 32. Such channels may facilitate the passage of oil, or other cooling fluid or medium, across the surface of the stator. Such channels 67 allow for increased cooling of the stator as the cooling fluid, such as oil, in these channels 67 may be in direct contact with the motor housing 70. There may be one cooling channel 67 per pole of the electric machine 10, which helps maintain magnetic symmetry.

[0250] In some embodiments, the cooling ducts 66 may have a cross section which is approximately rectangular, as illustrated in Figure 24. In one embodiment, the cooling ducts 66 may have a cross section which is 2.4 mm in the radial direction and 2.2 mm in the direction perpendicular to the radial direction. The radially outermost surface of the cooling duct 66 may be 0.6 mm from the outer surface 288 of the stator 20. The cooling channels 67 may be 5 mm deep in the radial direction and 3 mm wide in the direction perpendicular to the radial direction.

[0251] In some embodiments the cooling ducts 66 and, where present, cooling channels 67, may extend from a first end 22 of the stator 20 to a second end 122 of the stator 20 and be radially separated from the winding slots 40 by a section of stator core such that a minimum interference with flux is observed through the stator 20.

[0252] By having cooling ducts 66 and, where present, cooling channels 67, through the stator 20 a cooling fluid or medium can be passed through the stator 20 from the first end 22 of the stator 20 to the second end 122 of the stator 20 in order to transport heat, which is generated by the operation of the electrical stator windings 42 in the winding slots 40, away from the electric machine 10.

[0253] Each of the cooling ducts 66 may be positioned on a radial axis 46 of a corresponding winding slot 40.

[0254] By having the cooling ducts 66 on the radial axis 46 of an associated winding slot 40 the stator 20 may be optimally cooled whilst minimising the effect on the flux lines through the stator 20.

[0255] In some embodiments, there may be more cooling ducts 66 than winding slots 40 to facilitate greater cooling of the stator 20. Cooling ducts 66 positioned further away from the winding slots 40 have less effect on the flux lines through the stator 20 and can therefore be more numerous.

[0256] For example, Figure 25 illustrates a stator 20, suitable for a six pole motor, with an inner diameter bore 354 in the cylindrical inner channel 30 of the stator 20, and an outer diameter 352 of the stator 20. The stator 20 has a configuration of cooling ducts 66 and cooling channels 67 in accordance with those shown in Figure 24, the cooling ducts 66 being positioned close to the outer surface 288 of the stator 20, that is close to the extremities of the outer diameter 352. The cooling ducts 66 may be within 1 mm of the outer surface 288 of the stator 20, and may be at 0.6 mm from the outer surface 288 of the stator 20. In this configuration there are more cooling ducts 66 than winding slots 40 to facilitate stator cooling whilst minimising the effect on the flux through the stator 20. In this configuration there are six cooling channels 67, one per pole, open to the outside of the stator which may be in direct contact with a surrounding motor housing 70.

[0257] Figure 18 illustrates an embodiment of the invention with a cooling fluid flow extending from the first end 22 of the stator 20 to the second end 122 of the stator 20.

[0258] In order to provide such fluid flow, the motor housing 70 has a cooling fluid inlet 102 positioned between the first end 72 of the motor housing 70 and the first end 22 of the stator 20, in particular the terminal end 28 of the first end 22 of the stator 20.

[0259] The cooling fluid inlet 102 is therefore located in the proximity of the first end 22 of the stator 20 and arranged to provide a cooling fluid, such as oil or a dielectric fluid, to the first end 22 of the stator 20 in order for the cooling fluid to be passed or transported through the stator 20.

[0260] The motor housing 70 has a cooling fluid outlet 104 positioned between the second end 172 of the motor housing and the second end 122 of the stator 20, in particular the terminal end 128 of the second end 122 of the stator 20.

[0261] The cooling fluid outlet 104 is therefore located in the proximity of the second end 122 of the stator 20 and arranged to allow the expulsion of the cooling fluid, such as oil or a dielectric fluid, from the second end 122 of the stator 20 such that the cooling fluid can be removed from the motor housing 70 via the cooling fluid outlet 104. The cooling fluid is retained in radially outer chambers 106, 108 in the motor housing 70 due to the fluidic seal provided by the first tubular section 80 and the second tubular section 180.

[0262] This provides the advantage of allowing a cooling fluid to be controllably directed into a first end of the stator 20, and allows flow of cooling fluid through stator 20 in one direction to reduce the temperature of the electric machine 10.

[0263] In alternative embodiments, for example as shown in Figures 4, 5, 19, and 20 an oil inlet 110 is positioned centrally in the stator 20 via an aperture in the motor housing 70. The oil inlet 110 is positioned centrally between the first end 22 of the stator 20 and the second end 122 of the stator 20. The stator 22 comprises a first oil outlet 112 at, or in the proximity of, the first end 22 of the stator 20, and a second oil outlet 114 at, or in the proximity of, the second end 122 of the stator 20.

[0264] In some embodiments where the oil inlet 110 is positioned centrally in the stator 20, the stator 20 may be formed of an inner stator 36 and an outer stator 38. In such embodiments, the inner stator 36 may be formed of a continuous array of inner stator laminations from the first end 22 of the stator 20 to the second end 122 of the stator 20, and the outer stator 38 may be formed of a first set of outer stator laminations 116 and a second set of outer stator laminations 118, the first set of outer stator laminations 116 being separated from the second set of outer stator laminations 118 to form the oil inlet 110, as illustrated particularly in Figure 4 and Figure 5.

[0265] Figure 21 illustrates a cross section of a stator 20 comprising an inner stator 36 and an outer stator 38 where there are a plurality of cooling ducts 66 formed to transport a cooling fluid through the outer stator 38. In relation to the embodiments where the oil inlet 110 is positioned centrally in the stator 20 a first set of the plurality of cooling ducts 66 extends through the first set of outer laminations 116 from the oil inlet 110 to the first oil outlet 112 and a second set of the plurality of cooling ducts 66 extends through the second set of outer laminations 118 from the oil inlet 110 to the second oil outlet 114.

[0266] Manufacture of a stator 20 will now be described in relation to the stator 20 shown in Figure 23 and Figure 26, wherein the stator 20 may be formed as a two-part stator having an inner stator portion, or inner ring, 36 and an outer stator portion, or outer ring, 38.

[0267] Initially a stator lamina ring is cut or stamped from a sheet of steel material, the stator lamina ring comprising the material to form both the inner ring 36 and the outer ring 38 of the stator 20, and having a circular inner surface 286 and a substantially circular outer surface 288. In some stator arrangements the outer surface 288 may be oblate or comprise features which project from, or into, the outer surface 288 of the stator 20. For example, a keyway 234 may be provided in the outer surface 288 of the stator lamina ring, which would provide a keyway 234 in the outer ring 38 of the stator 20 once the inner ring 36 and outer ring 38 have been formed in subsequent cutting or stamping operations. Such deviations from a circular outer surface may reduce or prevent the possibility of the stator 20 rotating in a stator housing or motor housing 70, where the stator housing or motor housing 70 houses the stator 20 and may be affixed to a vehicle 300. The stator lamina ring is stamped, in a first stamping operation, to form an inner ring 36 and an outer ring 38. Following the first stamping operation, the inner ring 36 comprises a plurality of radially projecting teeth 214, each tooth 214 being connected to adjacent teeth 214 by respective material bridges 216 at radially inner ends 218 of the teeth 214, and being separated from the adjacent teeth 214 by respective winding slots 40, wherein the winding slots 40 of the inner ring 36 are open at radially outer ends 222 of the teeth 214, to receive electrical windings 42. The inner ring 36, illustrated in Figure 23, is complete following the first stamping of the stator lamina ring. The teeth 214 of the inner ring 36 are thereby separated from the outer ring 38 during the first stamping operation.

[0268] In some embodiments, at least some of the material bridges 216 are asymmetric in shape. In other embodiments all of the material bridges 216 are symmetric in shape.

[0269] Following the first stamping operation, the outer ring 38, comprises a first outer stator section 230 and a second outer stator section 232. The second outer section 232 may then be removed in a second stamping operation. In particular, this second stamping operation removes, from the outer ring 38, the areas of the outer ring 38 which are located at the position of the winding slots 40 of the inner ring 36, and may also optionally remove further material from the outer ring 38 which is located radially outboard of the teeth 214 of the inner ring 36, thereby to enlarge the gap between the outer ring 38 and the inner ring 36 at the location of the teeth 214 during the stamping operations. Alternatively, the first stamping operation and the second stamping operation may be carried out in a single stamping operation.

[0270] The optional removal of further material from the outer ring 38 which is located radially outboard of the teeth 214 of the inner ring 36 during the first stamping operation, may provide for modification of the size and shape of the aperture 64 provided between the electrical windings 42 in the winding slots 40 and the outer ring 38 allowing a cooling fluid, such as oil, to pass through the winding slots 40 from a cooling fluid inlet to a cooling fluid outlet via a cooling fluid channel as previously described.

[0271] In the embodiment shown in Figure 23, and shown in higher magnification in Figure 26, the radially outer end 222 of a tooth 214 comprises a first locating feature in the form of a projection 260 in the upper tooth surface 256. The projection 260 is bounded, particularly circumferentially bounded, at the radially outer end 222 of the tooth 214, by two tooth recesses 252-1 , 252-2 which are formed when the projection 260 is formed during manufacture. The projection 260 provides a locating and / or retention feature when adjacent to or abutting a corresponding second locating feature formed as part of the outer ring 38, for example a corresponding second locating feature in the form of an indentation surface 257 at an indentation 261 in the inner surface 255 of the outer ring 38, as shown in Figure 26.

[0272] The projection 260 in the upper tooth surface 256 of the tooth 214 may comprise a projection surface 262 in a central portion of the radially outer end 222 of the tooth 214, the projection surface 262 having a corresponding feature of the outer ring 38 in the form of an indentation 261 having an indentation surface 257, where the indentation surface 257 is recessed into the inner surface 255 of the outer ring 26 as illustrated in Figure 26, the indentation 261 being configured to receive the projection 260. The indentation surface 257 may abut or be in a push fit or an interference fit with the projection surface 262. In some embodiments the interference fit may be at least 0.035mm. The projection surface 162 and the indentation surface 257 may be considered to be azimuthal surfaces.

[0273] In some embodiments, the projection surface 262 may be planar or flat and may lie on a plane parallel to a width of the tooth 214, that is, the projection surface 262 may lie in a plane which is perpendicular to a radial axis 228-1 which projects from the central stator axis 32 to the centre of the projection surface 262. In other embodiments, the projection surface 262 may define an arc, which is a portion of the circumference of a circle centred on the central stator axis 32, having a radius which is equal to or substantially equal to the distance from the central stator axis 32 to an outer edge, or the upper tooth surface 256, of the radially outer end 222 of the tooth 214.

[0274] The two tooth recesses 252-1 , 252-2 are radially closer to the central stator axis 32 than the projection surface 262 of the projection 260. The first tooth recess 252-1 has a first tooth recess surface 264-1. The first tooth recess surface 264-1 has a corresponding feature on the outer ring 38 in the form of a first tooth recess receiving surface 259-1. The first tooth recess surface 264-1 may be considered to be an azimuthal surface.

[0275] The first tooth recess surface 264-1 may be planar or flat, that is, the first tooth recess surface 264-1 may lie in a plane which is perpendicular to a radial axis 228-2 which projects from the central stator axis 32 to the centre of the first tooth recess surface 264-1. In other embodiments, the first tooth recess surface 264-1 may define an arc, which is a portion of the circumference of a circle centred on the central stator axis 32, having a radius which is less than the distance from the central stator axis 32 to an outer edge, or the upper tooth surface 256, of the radially outer end 222 of the tooth 214. The second tooth recess 252-2 has a second tooth recess surface 264-2. The second tooth recess surface 264-2 has a corresponding feature on the outer ring 38 in the form of a second tooth recess receiving surface 259-2. The second tooth recess surface 264-2 may be considered to be an azimuthal surface.

[0276] The second tooth recess surface 264-2 may be planar or flat, that is, the second tooth recess surface 264-2 may lie in a plane which is perpendicular to a radial axis 228-3 which projects from the central stator axis 32 to the centre of the second tooth recess surface 264-2. In other embodiments, the second tooth recess surface 264-2 may define an arc, which is a portion of the circumference of a circle centred on the central stator axis 32, having a radius which is less than the distance from the central stator axis 32 to an outer edge, or the upper tooth surface 256, of the radially outer end 222 of the tooth 214.

[0277] As can be seen in Figure 23 and Figure 26 whilst the inner ring 36 and outer ring 38 are formed by a first stamping operation and a second stamping operation, or alternatively by a combined single stamping operation, when ultimately formed into a stator 20 each tooth 214 of the inner ring 36 is rotated in a circumferential direction by half of the separation between the centre of adjacent teeth 214 such that a tooth 214, and in particular the projection 260 on the tooth 214, resides in the location previously occupied by an adjacent winding slot 40, that is, at the location of the indentation 261 formed, during the stamping operation or operations, in the inner surface 255 of the outer ring 38. As the area of the outer ring 38 formed in this location was not formed by the stamping of the teeth 214 of the inner ring 36 from the stator lamina ring, it may be stamped such that the inner ring 36 and outer ring 38 are arranged to engage in a push fit or interference fit.

[0278] The interference fit between the inner ring 36 and the outer ring 38 may be limited to the projection surface 262 of the projection 260 at the radially outer end 222 of a tooth 214 of the inner ring 36 and the indentation surface 257 of the indentation 261 in the outer ring 38.

[0279] Figure 27 illustrates a vehicle 300 comprising an electric machine 10 as described above, where the electric machine may be used as a traction motor and / or generator. In some vehicles 300 a single electric machine 10 may be used to provide motive power to the vehicle 300. In other embodiments the vehicle 300 may have an electric machine 10 on each axle or at each wheel to provide motive power to the vehicle 300 and / or power generation for the vehicle 300. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. In particular, whilst the examples provided in Figures 1 to 26 illustrate various combinations of sealing arrangements, tubular section arrangements and cooling arrangements, it will be understood that the claimed invention is not limited to these specific examples but extends to other combinations of these arrangements as encompassed by the claims.

Claims

CLAIMS1. An electric machine comprising a stator having a cylindrical inner channel with a central stator axis, and a rotor coaxially located within the cylindrical inner channel of the stator, the rotor and stator being located, at least in part, within a motor housing, wherein the electric machine comprises: a first tubular section having a first end of circular cross section and a second end of circular cross section, the first end of the first tubular section located at a first end of the motor housing and the second end of the first tubular section located at a first end of the stator; and a second tubular section having a first end of circular cross section and a second end of circular cross section, the first end of the second tubular section located at a second end of the motor housing and the second end of the second tubular section located at a second end of the stator.

2. An electric machine according to claim 1 , wherein the second end of the first tubular section has an outer diameter substantially equal to the diameter of the cylindrical inner channel of the stator at the first end of the stator and the second end of the second tubular section has an outer diameter substantially equal to the diameter of the cylindrical inner channel of the stator at the second end of the stator.

3. An electric machine according to claim 1 or claim 2, wherein the motor housing comprises a first bearing housing at the first end of the motor housing against which the first end of the first tubular section is engaged.

4. An electric machine according to claim 3, wherein the first bearing housing comprises a section extending axially, parallel with the central stator axis, and against which an inner surface of the first end of the first tubular section is engaged.

5. An electric machine according to claim 4, wherein the axially extending section of the first bearing housing is circular in cross section and comprises an O-ring seal channel, around the circumference of the axially extending section of the first bearing housing, configured to retain an O-ring, wherein the O-ring is located between the axially extending section of the first bearing housing and the inner surface of the first end of the first tubular section.

6. An electric machine according to claim 5, wherein the axially extending section of the first bearing housing comprises a plurality of O-ring seal channels around the circumferenceof the axially extending section of the first bearing housing, each configured to retain an O- ring.

7. An electric machine according to any of claims 3 to 6, wherein the motor housing comprises a second bearing housing at the second end of the motor housing against which the first end of the second tubular section is engaged.

8. An electric machine according to claim 7, wherein the second bearing housing comprises a section extending axially, parallel with the central stator axis, and against which an inner surface of the first end of the second tubular section is engaged.

9. An electric machine according to claim 8, wherein the axially extending section of the second bearing housing is circular in cross section and comprises an O-ring seal channel, around the circumference of the axially extending section of the second bearing housing, configured to retain an O-ring, wherein the O-ring is located between the axially extending section of the second bearing housing and the inner surface of the first end of the second tubular section.

10. An electric machine according to claim 9, wherein the axially extending section of the second bearing housing comprises a plurality of O-ring seal channels around the circumference of the axially extending section of the first bearing housing, each configured to retain an O-ring.

11. An electric machine according to any of claims 1 to 10, wherein a terminal end of the first end of the stator comprises a chamfered section such that the inner diameter of the stator at the terminal end of the first end of the stator is larger than the inner diameter of a central section of the stator, and a terminal end of the second end of the stator comprises a chamfered section such that the inner diameter of the stator at the terminal end of the second end of the stator is larger than the inner diameter of the central section of the stator.

12. An electric machine according to any of claims 1 to 11 , wherein the second end of the first tubular section comprises a chamfered section having an outer diameter less than the diameter of the cylindrical inner channel of the stator at the first end of the stator and the second end of the second tubular section comprises a chamfered section having an outer diameter less than the diameter of the cylindrical inner channel of the stator at the second end of the stator.

13. An electric machine according to any of claims 1 to 12, comprising a guide located at the first end of the stator, wherein the guide comprises a chamfered section tapering towards the cylindrical inner channel of the stator.

14. An electric machine according to any preceding claim, wherein the first end of the stator, proximal to the first tubular section, comprises a first stator section and a second stator section, the first stator section of the first end of the stator being closer than the second stator section of the first end of the stator to a terminal end of the first end of the stator and providing a section of increased diameter bore in the cylindrical inner channel of the stator relative to the second stator section of the first end of the stator, the first stator section of the first end of the stator being configured to receive a length of the second end of the first tubular section to provide an overlap of the stator and the first tubular section parallel to the central stator axis.

15. An electric machine according to claim 14, wherein the increased diameter bore at the first stator section of the first end of the stator is provided by a plurality of stator laminations each having an increased diameter central aperture when compared to stator laminations of the second stator section of the first end of the stator located further from the terminal end of the first end of the stator.

16. An electric machine according to claim 14 or claim 15, wherein the length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis engages with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

17. An electric machine according to any of claims 14 to 16, wherein an axial seal is provided between a terminal end of the second end of the first tubular section and the second stator section of the first end of the stator.

18. An electric machine according to any of claims 1 to 13, wherein the first end of the stator, proximal to the first tubular section, comprises a first stator section and a second stator section, the first stator section of the first end of the stator being closer than the second stator section of the first end of the stator to a terminal end of the first end of the stator, and wherein a first end of the rotor, proximal to the first tubular section, comprises a first rotor section and a second rotor section, the second rotor section of the first end of the rotor being closer than the first rotor section of the first end of the rotor to a terminal end of the first end of the rotor and providing a section of decreased diameter rotor relative to the first rotor section of the first end of the rotor, the second rotor section of the first end of the rotor being configured to allowan overlap of the first stator section of the stator and the first tubular section parallel to the central stator axis.

19. An electric machine according to claim 18, wherein the first stator section of the first end of the stator is configured to receive a length of the second end of the first tubular section to provide an overlap of the stator and the first tubular section parallel to the central stator axis.

20. An electric machine according to claim 18 or claim 19, wherein the section of decreased diameter rotor provides a clearance gap between the rotor and the first tubular section when the first tubular section overlaps the stator parallel to the central stator axis.

21. An electric machine according to any of claims 18 to 20, wherein the length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis engages with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

22. An electric machine according to any of claims 18 to 20, wherein the length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis engages with an O-ring seal positioned between the second end of the first tubular section and the inner surface of the cylindrical inner channel of the stator.

23. An electric machine according to claim 22, wherein the length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis engages with a plurality of O-ring seals positioned between the second end of the first tubular section and the inner surface of the cylindrical inner channel of the stator.

24. An electric machine according to any of claims 18 to 23, wherein the first tubular section comprises a first portion of a first thickness and a second portion of a second thickness, the second portion of the first tubular section comprising a length of the second end of the first tubular section configured to overlap the stator parallel to the central stator axis, and wherein the thickness of the first portion of the first tubular section is greater than the thickness of the second portion of the first tubular section.

25. An electric machine according to claim 24, wherein an axial seal is provided between the end of the first portion of the first tubular section, closest to the first end of the stator, and a terminal end of the first end of the stator.

26. An electric machine according to any of claims 18 to 25, wherein the first rotor section of the first end of the rotor and the second rotor section of the first end of the rotor comprise different rotor configurations, the first rotor section of the first end of the rotor having a higher reluctance torque than the second rotor section of the first end of the rotor, optionally wherein the first rotor section of the first end of the rotor comprises a high reluctance torque permanent magnet rotor, and the second rotor section of the first end of the rotor comprises a high magnet-excitation torque rotor.

27. An electric machine according to any of claims 1 to 13, wherein the first end of the rotor is shorter than the first end of the stator along the direction of the central stator axis to allow an overlap of the stator and the first tubular section parallel to the central stator axis.

28. An electric machine according to claim 27, wherein the first stator section of the first end of the stator is configured to receive a length of the second end of the first tubular section to provide an overlap of the stator and the first tubular section parallel to the central stator axis.

29. An electric machine according to claim 28, wherein the length of the second end of the first tubular section which overlaps the stator parallel to the central stator axis engages with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

30. An electric machine according to any of claims 27 to 29, wherein there is no rotor located axially along the direction of the central stator axis that radially overlaps with the length of the second end of the first tubular section when the length of the second end of the first tubular section overlaps the stator.

31. An electric machine according to any of claims 1 to 10, wherein the second end of the first tubular section is adhered to the first end of the stator.

32. An electric machine according to claim 31 , wherein the axially outer lamination of the stator at the first end of the stator has a smaller inner diameter to provide a surface on which to adhere the second end of the first tubular section.

33. An electric machine according to claim 31 or claim 32, wherein adherence between the second end of the first tubular section and the first end of the stator is provided by a welded connection.

34. An electric machine according to claim 33, wherein the welded connection is a friction weld or a laser weld.

35. An electric machine according to any of claims 1 to 10 or 31 to 34, wherein the first tubular section comprises a sleeve and a toothed disc, the toothed disc being located at the second end of the first tubular section and being joined to the sleeve, the toothed disc comprising a plurality of teeth configured to overlap respective teeth of the stator when the first tubular section is located at the first end of the stator.

36. An electric machine according to claim 35, wherein the toothed disc located at the second end of the first tubular section is overmoulded onto the sleeve.

37. An electric machine according to claim 33 or claim 36, wherein the toothed disc forms a labyrinth mask providing a passage therethrough.

38. An electric machine according to any of claims 14 to 37, wherein the second end of the stator, proximal to the second tubular section, comprises a first stator section and a second stator section, the first stator section of the second end of the stator being closer than the second stator section of the second end of the stator to a terminal end of the second end of the stator and providing a section of increased diameter bore in the cylindrical inner channel of the stator relative to the second stator section of the second end of the stator, the first stator section of the second end of the stator being configured to receive a length of the second end of the second tubular section to provide an overlap of the stator and the second tubular section parallel to the central stator axis.

39. An electric machine according to claim 38, wherein the increased diameter bore at the first stator section of the second end of the stator is provided by a plurality of stator laminations each having an increased diameter central aperture when compared to stator laminations of the second stator section of the second end of the stator located further from the terminal end of the second end of the stator.

40. An electric machine according to claim 38 or claim 39, wherein the length of the second end of the second tubular section which overlaps the stator parallel to the central statoraxis engages with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

41. An electric machine according to any of claims 38 to 40, wherein an axial seal is provided between a terminal end of the second end of the second tubular section and the second stator section of the first end of the stator.

42. An electric machine according to any of claims 14 to 37, wherein the second end of the stator, proximal to the second tubular section, comprises a first stator section and a second stator section, the first stator section of the second end of the stator being closer than the second stator section of the second end of the stator to a terminal end of the second end of the stator, and wherein a second end of the rotor, proximal to the second tubular section, comprises a first rotor section and a second rotor section, the second rotor section of the second end of the rotor being closer than the first rotor section of the second end of the rotor to a terminal end of the second end of the rotor and providing a section of decreased diameter rotor relative to the first rotor section of the second end of the rotor, the second rotor section of the second end of the rotor being configured to allow an overlap of the first stator section of the second end of the stator and the second tubular section parallel to the central stator axis.

43. An electric machine according to claim 42, wherein the first stator section of the second end of the stator is configured to receive a length of the second end of the second tubular section to provide an overlap of the stator and the second tubular section parallel to the central stator axis.

44. An electric machine according to claim 42 or claim 43, wherein the section of decreased diameter rotor provides a clearance gap between the rotor and the second tubular section when the second tubular section overlaps the stator parallel to the central stator axis.

45. An electric machine according to any of claims 42 to 44, wherein the length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis engages with an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

46. An electric machine according to any of claims 42 to 44, wherein the length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis engages with an O-ring seal positioned between the second end of the second tubular section and the inner surface of the cylindrical inner channel of the stator.

47. An electric machine according to claim 46, wherein the length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis engages with a plurality of O-ring seals positioned between the second end of the second tubular section and the inner surface of the cylindrical inner channel of the stator.

48. An electric machine according to any of claims 42 to 47, wherein the second tubular section comprises a first portion of a first thickness and a second portion of a second thickness, the second portion of the second tubular section comprising a length of the second end of the second tubular section configured to overlap the stator parallel to the central stator axis, and wherein the thickness of the first portion of the second tubular section is greater than the thickness of the second portion of the second tubular section.

49. An electric machine according to claim 48, wherein an axial seal is provided between the end of the first portion of the second tubular section, closest to the second end of the stator, and a terminal end of the second end of the stator.

50. An electric machine according to any of claims 42 to 49, wherein the first rotor section of the second end of the rotor and the second rotor section of the second end of the rotor comprise different rotor configurations, the first rotor section of the first end of the rotor having a higher reluctance torque than the second rotor section of the first end of the rotor, optionally wherein the first rotor section of the second end of the rotor comprises a high reluctance torque permanent magnet rotor, and the second rotor section of the second end of the rotor comprises a high magnet-excitation torque rotor.

51. An electric machine according to any of claims 14 to 37, wherein the second end of the rotor is shorter than the second end of the stator along the direction of the central stator axis to allow an overlap of the stator and the second tubular section parallel to the central stator axis.

52. An electric machine according to claim 51 , wherein the first stator section of the second end of the stator is configured to receive a length of the second end of the second tubular section to provide an overlap of the stator and the second tubular section parallel to the central stator axis.

53. An electric machine according to claim 52, wherein the length of the second end of the second tubular section which overlaps the stator parallel to the central stator axis engageswith an inner surface of the cylindrical inner channel of the stator in an interference fit engagement.

54. An electric machine according to any of claims 51 to 53, wherein there is no rotor located axially along the direction of the central stator axis that radially overlaps with the length of the second end of the second tubular section when the length of the second end of the second tubular section overlaps the stator.

55. An electric machine according to any of claims 14 to 37, wherein the second end of the second tubular section is adhered to the second end of the stator.

56. An electric machine according to claim 55, wherein the axially outer lamination of the stator at the second end of the stator has a smaller inner diameter to provide a surface on which to adhere the second end of the second tubular section.

57. An electric machine according to claim 55 or claim 56, wherein adherence between the second end of the second tubular section and the second end of the stator is provided by a welded connection.

58. An electric machine according to claim 57, wherein the welded connection is a friction weld or a laser weld.

59. An electric machine according to any of claims 1 to 10 or 55 to 58, wherein the second tubular section comprises a sleeve and a toothed disc, the toothed disc being located at the second end of the second tubular section and being joined to the sleeve, the toothed disc comprising a plurality of teeth configured to overlap respective teeth of the stator when the first tubular section is located at the second end of the stator.

60. An electric machine according to claim 59, wherein the toothed disc located at the second end of the second tubular section is overmoulded onto the sleeve.61 . An electric machine according to claim 59 or claim 60, wherein the toothed disc forms a labyrinth mask providing a passage therethrough.

62. An electric machine according to any of claims 1 to 10, wherein the first tubular section is joined to the second tubular section via a third tubular section the third tubular section extending from the first end of the stator to the second end of the stator.

63. An electric machine according to claim 62, wherein the third tubular section has a thickness less than the first tubular section and the second tubular section.

64. An electric machine according to claim 62 or claim 63, wherein the first tubular section has an inner diameter smaller than the inner diameter of the second tubular section and the third tubular section, the inner diameter of the second tubular section being equal to the inner diameter of the third tubular section, and the outer diameter of the second tubular section is larger than the outer diameter of the first tubular section and the third tubular section, the outer diameter of the first tubular section being equal to the outer diameter of the third tubular section.

65. An electric machine according to any preceding claim, the stator comprising slots parallel to the central stator axis for retaining electrical windings, wherein apertures are provided between the electrical windings and the slots allowing oil to pass through the slots from an oil inlet to an oil outlet.

66. An electric machine according to claim 65, wherein the stator additionally comprises a plurality of cooling ducts through the stator, each of the plurality of cooling ducts extending substantially parallel to the central stator axis, from the first end of the stator to the second end of the stator.

67. An electric machine according to claim 65 or claim 66, wherein the oil inlet is at the first end of the stator and the oil outlet is at the second end of the stator.

68. An electric machine according to claim 65 or claim 66, wherein the oil inlet is positioned centrally in the stator between the first end of the stator and the second end of the stator, and the stator comprises a first oil outlet at the first end of the stator and a second oil outlet at the second end of the stator.

69. An electric machine according to claim 68, wherein the stator is formed of an inner stator and an outer stator wherein the inner stator is formed of a continuous array of inner stator laminations from the first end of the stator to the second end of the stator, and the outer stator is formed of a first set of outer stator laminations and a second set of outer stator laminations, the first set of laminations being separated from the second set of laminations to form the oil inlet.

70. An electric machine according to claim 69 when also dependent on claim 66, wherein a first set of the plurality of cooling ducts extends through the first set of outer laminations from the oil inlet to the first oil outlet and a second set of the plurality of cooling ducts extends through the second set of outer laminations from the oil inlet to the second oil outlet.

71. An electric machine according to any preceding claim, wherein an outer surface of the stator comprises channels parallel to the central stator axis to facilitate the passage of oil across the surface of the stator.

72. An electric machine according to any preceding claim, wherein the stator comprises winding slots extending parallel to the central stator axis, the winding slots each comprising a material bridge configured to provide a respective radially inner aperture for the passage of oil, each material bridge being asymmetrical and comprising a first portion comprising a first surface inside the winding slot and a second portion comprising a second surface inside the winding slot, the first surface and the second surface being radially separated by a third portion comprising a third surface, the third surface comprising a first curved section extending from an end of the first surface and a second curved section extending from an end of the second surface, wherein at least a portion of the second curved section overlaps one or more of the first surface and the first curved section along an axis parallel to the first surface.

73. A method of manufacture of a stator comprising: stamping a stator lamina ring to form an inner ring and an outer ring, the inner ring comprising a plurality of radially projecting teeth, each tooth being connected to adjacent teeth by respective material bridges at radially inner ends of the teeth, and being separated from the adjacent teeth by respective winding slots, wherein the winding slots of the inner ring are open at radially outer ends of the teeth; wherein, the radially outer end of at least one tooth is formed to comprise a first locating feature, the first locating feature being configured to be rotated in a circumferential direction by half of the separation between the centre of adjacent teeth and to abut, or be in an interference engagement with, a second locating feature in the outer ring; and wherein the outer ring, at the location from where the teeth of the inner ring are stamped and separated from the outer ring, is enlarged to form a cooling fluid channel through the winding slot.

74. A vehicle comprising an electric machine according to any of claims 1 to 72.

Images