The present disclosure relates to a method and apparatus for forming a coil pack for a stator of an axial flux electrical machine. In particular, the method and apparatus for forming a coil pack is for forming a substantially circular coil pack by reconfiguring a former from a first state to a second state.

Background

Electrical machines, including electric motors and electric generators, are widely used. However, concerns over our reliance on, and the pollution caused by, fossil fuel dependent internal combustion engines is increasing political and commercial pressures to extend the use of electrical machines to new applications, and to expand their use in existing ones. Electrical machines are increasingly being used in vehicles, such as electric cars, motorbikes, boats and aircraft. They are also used in energy generation, such as generators in wind turbines.

In order to meet the needs of these applications, it will be necessary to design electrical machines that have suitable performance properties and high efficiency. It will further be necessary to develop processes of making such electrical machines. Such new processes of making electrical machines may reduce the time needed to make new electrical machines, reduce complexity, or increase reliability.

One known type of electrical machine is the axial flux machine. As the name suggests, the direction of the lines of magnetic flux that are cut during the operation of an axial flux machine is parallel to the axis of rotation of the machine. This is in contrast to radial flux machines, in which the direction of the lines of magnetic flux that are cut during the operation of the machine is perpendicular to the rotation axis of the machine. While radial flux machines are more common, axial flux machines have been used for some applications where the form factor (a relatively small axial dimension) and performance properties (e.g. a high torque to weight ratio) of axial flux machines are essential.

As axial flux machines are less common, relatively less effort has been expanded to develop processes of, or apparatuses for, making such machines or components for such machines. It would be desirable to provide a method of, and apparatus for, forming a coil pack for a stator of an axial flux electrical machine which may allow for such a axial flux electrical machine to be more easily and accurately assembled.

Summary of Invention

Embodiments described herein provide a method and apparatus for forming a coil pack for a stator of an axial flux electrical machine which provide for ease of manufacture of a coil pack. The disclosure provides a method and an apparatus for forming a coil pack for a stator of an axial flux electrical machine, as defined in the appended independent claims, to which reference should now be made. Preferred or advantageous features of the disclosure are set out in the dependent sub-claims.

In a first aspect, the disclosure provides a method of forming a coil pack for a stator of an axial flux electrical machine. The method comprises the steps of providing N conductive coils, each of the N conductive coils comprising overlapping portions configured to overlap corresponding portions of adjacent ones of the N conductive coils; distributing at least a subset of the N conductive coils about an inside surface of a former, such that the N conductive coils are distributed without the overlapping portions of the first and the N ^th conductive coils overlapping; and reconfiguring the former from a first state, in which the former permits the distribution of the N conductive coils without the overlapping portions of the first and the N ^th conductive coils overlapping, to a second state, in which the former packs the N conductive coils such that the overlapping portions of each coil overlap the corresponding overlapping portions of respective adjacent coils to form a substantially circular coil pack.

The method according to the first aspect allows for a substantially circular coil pack to be formed in a reliable, repeatable, and efficient manner. As the former is reconfigured from the first to the second state in a predictable and repeatable manner, the substantially circular coil pack may be formed within narrow tolerances.

As used herein, the term “coil pack” refers to a collection, or grouping, of conductive coils in a predefined shape so as to enable the collection of conductive coils to form a component of a stator of an axial flux electrical machine. The coil pack may alternatively be referred to as a pack of conductive coils, a pre-stator, or a stator component.

Depending on the size of the coils, the desired dimensions of the coil pack, and the number of desired phases, N may be any suitable number. For example any number in the range from 10 to 200, or from 20 to 100, or from 40 to 60. In one particular embodiment, N may be 48. In this particular embodiment, each conductive coil of the N conductive coils may be made up of a pair of conductive elements, so that the total number of conductive elements is 96.

The step of reconfiguring the former may comprise moving at least one gate. Moving the at least one gate may, in particular, at least partially, close an opening in a circumference of the former. This may allow for the former to be reconfigured in a repeatable and simple manner.

The former may comprise the at least one gate or the at least one gate may be provided separately from the former, i.e. as a separate element. The gate is movable relative to the former. If there is more than one gate, each gate may form part of the former or may be provided separately, or one or more gates may form part of the former and one or more other gates may be provided separately.

The gate, whether it has articulated joints or not, may be hingedly attached to the former.

The or each gate may comprise at least one articulated joint, and the step of moving the or each gate comprises moving the at least one articulated joint. The gate may be akin to a robotic arm having multiple articulated joints which are moveable independently from one another. This may allow the gate to reconfigure in shape, i.e. from a straight gate to a curved gate.

In one particular embodiment, the former comprises one gate. In an alternative particular embodiment, the former comprises two gates. As will be appreciated, where applicable, the features of a gate described herein apply to embodiments where the former comprises one gate, and to embodiments where the former comprises two gates.

The former may comprise a single hinge but two gates. For example, if the former comprises two portions attached to one another by a hinge, and both portions move to reconfigure the former into the second state, the pincer-like movement may advantageously provide a simple and repeatable mechanism.

The gate may be attached to the static portion of the former by an articulated joint. Alternatively, the gate may not be attached to a static portion of the gate, because it is a separate component or because there is no static portion.

In alternative embodiment, the former may comprise a tensioning device, configured to provide circumferential tension to the former, so that reconfiguring the former from a first to the second state comprises reducing the diameter of the inside surface of the former consistently around the entire circumference of the former.

The or each gate may comprise a shaped portion, such that upon reconfiguring the former to the second state, the shaped portion aligns with, and/or forms a portion of, the inside surface of the former, so as to pack the N conductive coils to form the substantially circular coil pack. By aligning a shaped portion of the former with the inside surface of the former, the N conductive coils of the coil pack may be packed so as to form the substantially uniform, circular shape.

Upon the former being in the first state, the inside surface of the former may be substantially “C”- shaped. A “C”-shape may allow for (at least a subset of) the N conductive coils to easily be introduced into, and distributed about an inside surface of, the former. For example, the step of distributing at least a subset of the N conductive coils about the inside surface of the former may comprise conveying the N conductive coils along a predefined path. The predefined path may follow the inside surface of the former. A straight portion of the predefined path, leading into the former via the opening, may be provided at an angle 0 relative to the inner surface of the former at the opening. Alternatively, the straight portion may lead into the former in a straight line, that is at an angle 0 of 180 degrees relative to the inner surface of the former.

When the N conductive coils are conveyed along a predefined path, the step of providing the N conductive coils comprises aligning the N conductive coils on a conveyor. In particular, each N conductive coil may comprise an attachment portion configured for reversible attachment to a respective attachment portion of the conveyor.

The conveyor may be a continuous belt having recesses for receiving the attachment portions of the conductive coils. For example, the recesses may be holes for receiving a tail of each conductive coil acting as the attachment portion.

Alternatively, the former may comprise a base plate having a slot, or a channel. The N conductive coils may be pushed along the base plate, guided by said slot or channel, towards the opening. The N conductive coils may be pushed manually, by an actuator, or by a conveyor comprising a continuous belt preferably having recesses for receiving the attachment portions of the conductive coils.

Alternatively, the step of distributing at least a subset of the N conductive coils about the inside surface of the former comprises individually picking each of the N conductive coils, or a subset of the N conductive coils, and placing each of the N conductive coils, or each subset, at a respective position in the former. In some embodiments, the respective position in the former may be the same for each of the N conductive coil. That is, each coil may be placed in the same position. In these embodiments, the method may further comprise rotating a base, preferably a circular base, before placing the next one of the N conductive coils, so that the N conductive coils are distributed in a substantially circular fashion.

The method may comprise providing a robotic manipulator. The robotic manipulator may individually pick each of the N conductive coils and may individually place each of the N conductive coils at a respective position in the former. Preferably, the respective position in the former is the same for each of the N conductive coil.

The method may further comprise holding coils distributed about the inside surface of the former. Holding the coils distributed about the inside surface of the former may comprise providing a holding pin for holding the coils together (i.e. preventing misalignment). The holding pin may be rotated with the rotating (circular) base. The holding pin may be assisted in holding the coil by the shape of the coils.

Alternatively, providing the N conductive coils and/or distributing at least a subset of the N conductive coils about the inside surface of the former may comprise providing at least some of the N conductive coils to a cassette, wherein the cassette comprises a plurality of cavities, each cavity configured to removably receive one of the N conductive coils.

The N conductive coils may be provided in a line, such that the first of the N conductive coils overlaps the second of the N conductive coils, each of the second to N-1 ^th conductive coils overlaps two respective adjacent conductive coils, and the N ^th conductive coil overlaps the N-1 ^th conductive coil. This may facilitate packing into the substantially circular coil pack, as the N conductive coils are already overlapping while at least the subset of the N conductive coils are distributed about the inside surface of the former. This may allow for the shape of the coil pack to be more easily and consistently achieved, and may reduce the manufacturing time by increasing the efficiency.

If the step of providing the N conductive coils comprises using a hopper or pick and place mechanism which are configured to repeatedly provide a subsequent conductive coil to the same position within the former, or if the conductive coils are manually provided to the same position, the former may comprise a rotatable base, and the method may further comprise rotating said rotatable base.

Rotating said rotatable base may be automated by providing a sensor for determining when a subsequent conductive coil (or a subsequent set of conductive coils) has been placed in the former, and rotating the rotatable base a corresponding distance about an axis through a centre of the rotatable base and the former, so that the next conductive coil (or set of conductive coils) may be provided to the same position.

For example, if N is 48, and the conductive coils are individually inserted, the rotatable base may be rotated about 7.5 degrees about the centre axis after each conductive coil is inserted, so that, after all 48 conductive coils have been inserted, the rotatable base has been rotated one full turn, i.e. about 360 degrees.

The step of reconfiguring the former to the second state may pack the N conductive coils such that the circular coil pack comprises spaces for receiving flux guides, wherein the method further comprises a step of aligning the N conductive coils such that each space for receiving a flux guide is substantially identical. Aligning the N conductive coils may facilitate insertion of flux guides.

The inside surface of the former, and if present, the shaped portion of the or each gate, may comprise slots, or recesses, for aligning the N conductive coils. For example, cut-outs, or recesses, in the inside surface may be spaced evenly around the circumference of the inside surface, so as to distribute, and space out, the N conductive coils substantially evenly. The slots may provide for an initial alignment before the step of aligning the N conductive coils, or may be sufficient to ensure that each space for receiving a flux guide is substantially identical.

In alternative embodiments of the method, the former may comprise coil retaining pins which are configured to retain the coils when occupying the spaces for flux guides formed in the stator by the overlapping coils.

In some embodiments, the former may comprise two semi-circular portions.

In these embodiments in which the former comprises two semi-circular portions, reconfiguring the former from a first state to a second state may comprise moving at least one of the two semicircular portion towards the other semi-circular portion so that some of the coils in each semicircular portion overlap.

In some embodiments, distributing at least a subset of the N conductive coils about an inside surface of a former may comprise placing at least some coils of the subset of the N conductive coils onto coil retaining pins of the former. In these embodiments, distributing at least a subset of the N conductive coils may comprise distributing half of the N conductive coils about the inner surface of a first semi-circular portion by placing coils onto coil retaining pins of a first semicircular portion of the former, and distributing the other half of the N conductive coils about the inner surface of a second semi-circular portion by placing coils onto coil retaining pins of the second semi-circular portion. Thus half the N conductive coils may be retained by the retaining pins of the first semi-circular portion, and the other half of the N conductive coils may be retained by the retaining pins of the second semi-circular portion.

In some embodiments in which the former comprises two semi-circular portions and in which distributing at least a subset of the N conductive coils about an inside surface of a former comprises placing at least some coils of the subset of the N conductive coils onto coil retaining pins of the former, the end coils of each semi-circular portion may overlap when the portions are brought together. This may be enabled by the retaining pins at respective ends of the semicircular portions being shorter than the other retaining pins, thus allowing overlap of the ends of the halves of the N conductive coils to form the coil pack.

The retaining pins may be provided so as to occupy only some of the spaces for flux guides, for example every second space for flux guides (of the formed stator).

In embodiments in which the former comprises retaining pins, the method may comprise retracting the retaining pins after the coil pack has been formed.

The method may further comprise a step of inserting flux guides into the spaces. The step of inserting flux guides into the spaces may comprise arranging the flux guides in a pattern which substantially corresponds to the pattern of the spaces in the circular coil pack, before substantially simultaneously inserting the flux guides.

Alternatively, providing the flux guides in the pattern may comprise providing the flux guides to a cassette, wherein the cassette comprises a plurality of cavities, each cavity configured to removably receive one of the plurality of flux guides, the plurality of cavities provided in a pattern which substantially corresponds to the pattern of the spaces in the circular coil pack.

The flux guides may be provided to the cassette manually, or by a hopper or pick and place mechanism. If the flux guides are provided by a hopper or pick and place mechanism, the cassette may be rotatable, so that when the hopper or pick and place mechanism provides the flux guides to the same position, the flux guides can be provided in the pattern.

Only a subset of flux guides may be provided in a pattern and inserted simultaneously, e.g. half the flux guides may be inserted simultaneously, and the steps of providing and inserting the flux guides may be repeated for the other half of flux guides.

In a further alternative, the step of inserting the flux guides into the spaces comprises individually aligning and individually inserting flux guides into a respective space.

The step of individually aligning and individually inserting the flux guides may comprise using a shuttle to individually align and insert each flux guide.

The shuttle may be tapered. Tapering the shuttle may protect misaligned coils from damage, and may compensate for variation in coil and flux guide dimensions.

The shuttle may be larger than the flux guide. The shuttle may be larger than the flux guide by about 0.5% to about 10%, or by about 1% to about 5%, or by about 2%.

The shuttle being larger than the flux guide may refer to the shuttle being wider than the flux guide, i.e. the shuttle being larger than the flux guide in a dimension perpendicular to a longitudinal dimension of the flux guide. The shuttle being larger than the flux guide may refer to the shuttle being larger than the flux guide in all dimensions.

The method may further comprise a step of attaching the, or each, flux guide to an electromagnet before the step of inserting flux guides into the spaces.

The flux guides may be attached to the electromagnet manually, using a hopper or pick and place mechanism, or from a cassette. The method may further include using locating guides for locating respective ones of the spaces.

In the alternative embodiments in which the former comprises retaining pins, the step of inserting flux guides into the spaces may comprise inserting flux guides into the spaces not occupied by retaining pins. For example, if every second space is occupied by retaining pins, the step of inserting flux guides may comprise inserting flux guides into the spaces not occupied by retaining pins. In these alternative embodiments, the method may further comprise retracting the retaining pins, and then inserting flux guides into the empty spaces previously occupied by the retaining pins. The step of inserting the flux guides into spaces in the coil pack may comprise attaching a locating guide to each flux guide. Each locating guide may comprise a shaped tip for locating a respective one of the spaces. The locating guides may further be configured to perform the step of aligning the N conductive coils such that each space for receiving a flux guide is substantially identical.

Where the method comprises attaching the, or each, flux guide to an electromagnet, the locating guides may be ferromagnetic, such that respective locating guides are attached to each flux guide using the electromagnet. In this embodiment, the method may further comprise a step of switching off the electromagnet after the flux guides have been inserted into the spaces, to detach the locating guides from the flux guides. This may allow for the locating guides to be easily attached to, and detached from, the flux guides without any need for physical or destructive means.

The step of inserting the flux guides and the step of locating the spaces may be one step. Alternatively, once the locating guides have located the spaces, and optionally aligned the N conductive coils, the flux guides may be inserted into respective spaces.

Aligning and inserting the, or each, flux guide may comprise moving, e.g. rotating or linearly actuating, the electromagnet relative to the coil pack to align the, or each, flux guide with a respective space. Alternatively, the method may comprise rotating, or otherwise moving, the coil pack to align the, or each, flux guide and the, or each, respective space.

In a second aspect, the disclosure provides a method of forming a stator for an axial flux electrical machine. The method according to the second aspect comprises forming a substantially circular coil pack as described herein, and placing the coil pack in a stator housing.

The method may further comprise transferring the coil pack using a, or the, electromagnet, the electromagnet engaging with the flux guides. As will be appreciated, the flux guides and the coil pack are preferably configured such that an interference fit is provided between the coil pack and the flux guides. This may allow for the formed coil pack to be moved more easily, and without any risk of damaging the coil pack.

The coil pack may alternatively be lifted by a robotic manipulator and placed into the stator housing.

The method may further comprise providing at least one guide, or lead-in tool, for aligning the coil pack and the stator housing. The at least one guide may be provided as a (removable) component of the stator housing. Providing the guide as a removable component of the housing may comprise bolting the guide to the stator housing. Alternatively, the at least one guide may not be a part of the stator housing and instead providing at least one guide may comprise introducing the at least one guide into a path of the coil pack as the coil pack is being placed into the stator housing, so as to align the coil pack and the stator housing. The at least one guide may be configured to align the coil pack with the stator housing, and may be configured to be removed after alignment.

The method may further comprise sandwiching the coil pack. Sandwiching the coil pack may facilitate insertion of the coil pack into the stator housing.

In some embodiments, the method may further comprise, following insertion of the flux guides, horizontally moving the coil pack. Horizontally moving the coil pack may comprise sandwiching the coil pack and guiding the coil pack into the stator. Guiding the coil pack into the stator may comprise using at least one guide, as set out above.

The inner surface of the stator housing may comprise fingers configured to interdigitate the coils of a stator when the stator has been inserted into the stator housing.

The guide may further comprise flexible inserts, positioned at an “upper” end of the fingers (i.e. the end of the fingers that first engage with the coils upon insertion of the stator) configured to deform over sharp edges of the stator housing upon insertion of the stator into the stator housing, so as to prevent scratching of the stator. Alternatively, the flexible inserts may be provided separately from the guide, e.g. as a flexible ring-shaped element, such that the method comprises a separate step of providing flexible inserts.

Optionally, the number of inserts is identical to the number of fingers, i.e. there is one insert per finger.

The flexible inserts may be made of plastic, for example an aramid polymer fibre such as Nomex, or Kevlar.

The flexible inserts may be removed together with the guide, or in a separate step.

The method may further comprise a step of providing covers over the fingers. The method may comprise clipping the covers onto the fingers of the stator housing. The covers may be shaped to hold the coil centred between the fingers, to protect the coil from scratching.

The method may further comprise a step of providing and connecting at least one busbar to the circular coil pack.

In a third aspect, the disclosure provides an apparatus for forming a coil pack for a stator of an axial flux electrical machine. The apparatus comprises a former, having an inside surface, configurable from a first state, in which the former is configured to receive at least a subset of N conductive coils, each of the N conductive coils comprising portions configured to overlap corresponding portions of adjacent ones of the N conductive coils, without the overlapping portions of the first and the N ^th conductive coils overlapping, to a second state, in which the former is configured to pack the N conductive coils such that the overlapping portions of each coil overlap corresponding overlapping portions of respective adjacent coil to form a substantially circular coil pack.

The inside surface of the former, in the first state, may be substantially “C”-shaped.

The apparatus may comprise at least one gate configured to, in the second state, close an opening in a circumference of the former. The former may optionally comprise the at least one gate and/or the at least one gate may be provided separately from the former.

The or each gate comprises at least one articulated joint.

The or each gate may comprise a shaped portion configured to align with, and/or form a portion of, the inside surface of the former upon the former being in the second state, so as to pack the N conductive coils to form the substantially circular coil pack.

The apparatus may further comprise a conveyor configured to convey the N conductive coils along a predefined path. The predefined path may follow the inside surface of the former. The predefined path may comprise a straight portion. The straight portion leads into the former via the opening, and may be provided at an angle 0 relative to the inner surface of the former. Alternatively, the straight portion may lead into the former in a straight line, that is at an angle 0 of 180 degrees.

The conveyor may be a continuous belt having recesses for attaching the attachment portions of the conductive coils. For example, the recesses may be holes for receiving a tail of each conductive coil acting as the attachment portion.

Alternatively, the former may comprise a base plate having a slot, or a channel. The N conductive coils may be pushed along a straight line by a continuous belt towards the opening, so that the N conductive coils are pushed through into and along the slot.

The conveyor may be configured to receive a line of the N conductive coils, such that the first of the N conductive coils overlaps the second of the N conductive coils, each of the second to N-1 ^th conductive coil overlaps two respective adjacent conductive coils, and the N ^th conductive coil overlaps the N-1 ^th conductive coil.

Instead of a conveyor, the apparatus may comprise a robotic manipulator. The robotic manipulator may be configured to individually pick each of the N conductive coils and place each of the N conductive coils at a respective position in the former. The respective position in the former may be the same for each of the N conductive coil. That is, each coil may be placed in the same position (relative to the robotic manipulator). In these embodiments, the apparatus may further comprise a rotatable base configured to be rotated before placing the next one of the N conductive coils. This may allow for the N conductive coils to be distributed about an inside surface of the former, while using a robotic manipulator to place each of the N conductive coils in the same position.

The former may be configured so that the substantially circular coil pack comprises a plurality of spaces, each space being for receiving a flux guide.

The apparatus may further comprise at least one of: an alignment device for aligning the N conductive coils such that each space for receiving a flux guide is substantially identical; an electromagnet for inserting a plurality of flux guides into the spaces in the coil pack; a cassette for aligning the flux guides, wherein the cassette comprises a plurality of cavities, each cavity configured to removably receive one of the plurality of flux guide, the plurality of cavities provided in a pattern which substantially corresponds to a pattern of the spaces in the circular coil pack; and an inserting device for individually inserting flux guides into the spaces.

In some embodiments, the inserting device may be a shuttle for inserting flux guides into the spaces. The shuttle may be configured to individually align and individually insert the flux guides.

The shuttle may be configured to move reciprocally to insert flux guides into the spaces.

The shuttle may be tapered. Tapering the shuttle may protect misaligned coils from damage, and may compensate for variation in coil and flux guide dimensions.

The shuttle may be larger than each flux guide. This may prevent leading edges of the flux guides from being damaged.

The shuttle may be larger than the flux guide by about 0.5% to about 10%, or by about 1% to about 5%, or by about 2%.

The shuttle being larger than the flux guide may refer to the shuttle being wider than the flux guide, i.e. the shuttle being larger than the flux guide in a dimension perpendicular to a longitudinal dimension of the flux guide. The shuttle being larger than the flux guide may refer to the shuttle being larger than the flux guide in all dimensions.

The shuttle may be coated with a relatively softer material to prevent any damage to the coils, e.g. to a protective insulation of the coils.

When the apparatus comprises an alignment device, the alignment device may comprise a rotatable base. The rotatable base may comprise slots, each slot being for receiving one of the N conductive coils.

Alternatively, the alignment device may comprise slots, or recesses, for aligning the N conductive coils provided in the inside surface of the former, and if present, the shaped portion of the or each gate. For example, cut-outs, or recesses, in the inside surface may be spaced evenly around the circumference of the inside surface, so as to distribute, and space out, the N conductive coils substantially evenly. The slots may provide for an initial alignment before the step of aligning the N conductive coils, or may be sufficient to ensure that each space for receiving a flux guide is substantially identical.

The alignment device may comprise multiple components, e.g. the slots in the rotatable base may provide an initial distribution and alignment, and the slots in the inside surface of the former may provide a finer alignment once the former is reconfigured into the second state.

The apparatus may further comprise at least one holding pin for holding coils distributed about the inside surface of the former. The holding pin may be configured to be moved so that it engages one of the coils already distributed about the inside surface of the former. In particular, the holding pin may be configured to engage a first one of the coils inserted into the former, or a last coil inserted into the former (i.e. the coil the holding pin engages may change upon insertion of a further coil). The holding pin may be configured to move by rotating with a, or the, rotatable base. Providing a rotatable base may allow for each of the N conductive coils to be provided in the same position, while the holding pin may prevent coils already distributed about the inside surface of the former from becoming misaligned or disengaged.

Upon the apparatus comprising the electromagnet, the apparatus may further comprise an attachment device for individually attaching flux guides to the electromagnet in a pattern which substantially corresponds to a pattern of the spaces in the circular coil pack. The attachment device may be a hopper, a pick and place mechanism, or a pneumatic device.

Each of the flux guides may comprise a locating guide. The locating guides may be ferromagnetic. Each locating guide may comprise a shaped tip for locating a respective one of the spaces.

Alternatively, the locating guides may be glued, or otherwise temporarily attached, to the flux guides.

In some embodiments, the former may comprise coil retaining pins which are configured to retain the coils, e.g. when the coil retaining pins occupy the spaces for flux guides formed in the stator by the overlapping coils. The retaining pins may be provided in addition, or as an alternative, to the at least one holding pin.

The retaining pins may be provided in such a number, and in a pattern, so as to occupy only some of the spaces for flux guides, for example every second space for flux guides.

The retaining pins may be retractable, so that they may be retracted from the formed stator, i.e. when the former is in the second state.

In some embodiments, the former may comprise two semi-circular portions. In some embodiments in which the former comprises two semi-circular portions, the former may comprise two holding pins, one for each semi-circular portion.

In embodiments in which the former comprises two semi-circular portions, the retaining pins may be arranged in two semi-circular portions of the former such that half of the N conductive coils may be distributed about the inner surface of the first semi-circular portion, and the other half of the N conductive coils may be distributed about the inner surface of the second semi-circular portion. Thus, half the N conductive coils may be retained by the retaining pins of the first semicircular portion, and the other half of the N conductive coils may be retained by the retaining pins of the second semi-circular portion.

The former may be reconfigurable from the first state to the second state by moving at least one of the two semi-circular portions towards the other of the two semi-circular portions, so as to overlap, and bind together, the first half and the other half of the N conductive coils.

For this purpose, in some embodiments in which retaining pins are provided, the retaining pins at respective ends of the semi-circular portions may be shorter than the other retaining pins.

For example, the final two retaining pins of each of the semi-circular portions at one end may be about half the length of the remaining retaining pins. This may enable the ends of “half stators” to overlap.

In some embodiments, both retaining pins and at least one holding pin may be provided. In some embodiments, providing only one of retaining pins and at least one holding pin may be sufficient for holding the coils distributed about the inside surface of the former.

In a fourth aspect, the present disclosure provides a system for making a stator. The system comprises an apparatus according to the third aspect of the disclosure; and an electromagnet for placing the circular coil pack into a stator housing. Optionally, the electromagnet may further be for transferring the circular coil pack. In some embodiments, the system comprises at least one guide for aligning the coil pack and the stator housing. The at least one guide may be provided as a (removable) component of the stator housing. Alternatively, the at least one guide may be a separate component of the system.

The at least one guide may be configured to be introduced into the path of the coil pack. The guide may be configured to align the coil pack with the stator housing, and may be configured to be removed after, or during, alignment.

The inner surface of the stator housing may comprise fingers configured to interdigitate the coils of the stator.

The guide may further comprise flexible inserts, to be placed at the “upper” end of the fingers (i.e. those ends that first engage with the coils) configured to deform over sharp edges of the stator housing upon insertion of the stator into the stator housing, so as to prevent scratching of the stator.

Alternatively, the system may comprise flexible inserts which are separate from the guide, e.g. as a flexible ring-shaped element. Optionally, the number of inserts is identical to the number of fingers, i.e. there is one insert per finger.

The flexible inserts may be made of plastic, e.g. thin plastic sheet, for example an aramid polymer fibre such as Nomex, or Kevlar.

The system may further comprise covers for (at least some of) the fingers. The covers may be clipped over the fingers, i.e. they may be sized so as to be received on the fingers. The covers may be shaped to hold the coils centred between the fingers, so as to protect the stator from scratching.

For example, the covers may be in the shape of a “W”, or a “M”, with the central slot fitting over the finger, and the two outer slots being configured to respectively receive one coil of each pair of coils.

The method may further comprise a step of providing and connecting at least one busbar to the circular coil pack.

The system may further comprise a connecting device for connecting a busbar to the circular coil pack.

In a further aspect, the present disclosure provides a system for making a stator. The system comprises an apparatus according to the third aspect of the disclosure; and a linear actuator for horizontally moving the coil pack into a stator housing.

The system may further comprise an engagement means for engaging a base and a top of the coil pack for sandwiching the coil pack. Sandwiching the coil pack may facilitate insertion of the coil pack into the stator housing. The system may be configured to sandwich the coil pack using the engagement means before or after horizontally moving the coil pack.

In some embodiments of the further aspect, the system comprises at least one guide for aligning the coil pack and the stator housing. The at least one guide may be provided as a (removable) component of the stator housing. Alternatively, the at least one guide may be a separate component of the system.

The at least one guide may be configured to be introduced into the path of the coil pack. The guide may be configured to align the coil pack with the stator housing, and may be configured to be removed after, or during, alignment.

In a fifth aspect, the disclosure provides a method of inserting flux guides into a coil pack for a stator of an axial flux electrical machine. The method comprises the steps of: providing a substantially circular coil pack comprising spaces for receiving flux guides; attaching a plurality of flux guides to an electromagnet in a pattern which substantially corresponds to the pattern of spaces in the circular coil pack; aligning the electromagnet and the circular coil pack so that each flux guide is substantially aligned with a respective space in the circular coil pack; and moving at least one of the circular coil pack and the electromagnet relative to one another so as to insert each flux guides into the respective space in the circular coil pack.

The method may further comprise aligning the N conductive coils such that each space for receiving a flux guide is substantially identical.

When the method comprises providing the flux guides in the pattern, providing the flux guides in the pattern may comprise providing the flux guides to a cassette, wherein the cassette comprises a plurality of cavities, each cavity configured to removably receive one of the plurality of flux guides, the plurality of cavities provided in a pattern which substantially corresponds to the pattern of the spaces in the circular coil pack.

The step of inserting the flux guides into the spaces may comprise individually aligning and individually inserting flux guides into a respective space.

The step of inserting the flux guides into spaces in the coil pack may comprise attaching a locating guide to each flux guide. Each locating guide may comprise a shaped tip for locating a respective one of the spaces.

The locating guides may be configured to perform the step of aligning the N conductive coils such that each space for receiving a flux guide is substantially identical.

The locating guides may be ferromagnetic, so as to be engageable by an electromagnet. Where the locating guides are ferromagnetic, the method may further comprise switching off the electromagnet after the flux guides have been inserted into the spaces to detach the locating guides from the flux guides.

In a sixth aspect, the disclosure provides a method of inserting flux guides into a coil pack for a stator of an axial flux electrical machine. The method comprises the steps of: providing a substantially circular coil pack comprises spaces for receiving flux guides; placing a plurality of flux guides into a cassette, the cassette comprising a plurality of cavities, each cavity configured to removably receive one of the plurality of flux guide, the plurality of cavities provided in a pattern which substantially corresponds to a pattern of the spaces in the circular coil pack; aligning the cassette and the circular coil pack, so that each flux guide is substantially aligned with a corresponding space in the circular coil pack; and moving at least one of the circular coil pack and the cassette relative to one another to insert the flux guides into the spaces in the circular coil pack. It will be appreciated that features described in relation to one aspect of the present disclosure may also be applied equally to all of the other aspects of the present disclosure. Features described in relation to the first aspect of the present disclosure may be applied equally to the second, third, fourth, fifth, and sixth aspects of the present disclosure and vice versa. For example, method features described in relation to the first and second aspects may be applied, mutatis mutandis, to the apparatus of the third aspect and the system of the fourth aspect of the disclosure.

It will further be appreciated that particular combinations of the various features described and defined in any aspects of the invention may be implemented and/or supplied and/or used independently.

Description of Specific Embodiments of the Invention

Specific embodiments of the invention will now be described with reference to the figures, in which:

Figure 1 shows a flow diagram of a method embodying the present disclosure;

Figure 2 shows a flow diagram of a further method embodying the present disclosure;

Figure 3 shows a flow diagram of a further method embodying the present disclosure;

Figure 4 shows a flow diagram of a further method embodying the present disclosure;

Figure 5 shows a flow diagram of a further method embodying the present disclosure;

Figure 6 shows a flow diagram of a further method embodying the present disclosure;

Figure 7 shows a flow diagram of a further method embodying the present disclosure;

Figure 8 shows a flow diagram of a further method embodying the present disclosure;

Figure 9 shows a flow diagram of a further method embodying the present disclosure;

Figure 10A shows plan and underneath views of a conductive coil having a single pair of radially extending active sections;

Figure 10B shows two perspective views of the conductive coil element of Figure 10A; Figure 11 A is a plan view of part of a coil pack that includes a plurality of the conductive elements of Figures 10A and 10B circumferentially distributed around the coil pack, showing spaces resulting from their overlap;

Figure 11 B is a plan view showing the coil pack of Figure 11 A;

Figure 12A shows plan and underneath views of a conductive coil that includes two pairs of circumferentially overlapping radially extending active sections connected in series;

Figure 12B shows two perspective views of the conductive coil of Figure 12A;

Figure 13 is a perspective view of the conductive components of a stator assembly of an axial flux machine that includes 48 conductive coils;

Figure 14 shows a flow diagram of an insertion method embodying the present disclosure;

Figure 15 shows a flow diagram of a further insertion method embodying the present disclosure;

Figure 16A shows plan views of a coil pack before and after reconfiguration of a former;

Figure 16B shows perspective views of the coil pack of Figure 16A;

Figure 17A shows a schematic of an example former according to the present disclosure;

Figure 17B shows a schematic of another example former according to the present disclosure;

Figure 18A shows a schematic of another example former according to the present disclosure;

Figure 18B shows schematics of another example former according to the present disclosure, in which the former has a conveyor;

Figure 18C shows an example lamination pack and alignment tool;

Figures 19, 20, 21 A and 21 B show perspective views of another example former according to the present disclosure;

Figures 22 and 23 show perspective views of a system according to the present disclosure; and

Figures 24A and 24B show top and perspective views of a cover for use in the system of Figures 22 and 23.

Specific description Figures 1 illustrates an example method 100 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. The method 100 comprises a step 102 of providing N conductive coils.

N may be any suitable number of conductive coils for forming a coil pack. In one particular example, N may be 48. However, depending on the size of the coils, the desired dimensions of the coil pack, and the number of desired phases, N may be any suitable number.

Each of the N conductive coils comprises overlapping portions configured to overlap corresponding (overlapping) portions of adjacent ones of the N conductive coils. The conductive coils will be further described below with reference to the exemplary conductive coils of Figures 10 to 13, although any suitable conductive coils may be used.

The method 100 further comprises a step 104 of distributing at least a subset of the N conductive coils about an inside surface of a former. The N conductive coils are distributed such that the overlapping portions of the first conductive coil do not overlap respective overlapping portions of the N ^th conductive coil. The overlapping portions of any of the other N conductive coils may or may not be overlapping corresponding overlapping portions of adjacent conductive coils.

Although all of the N conductive coils may be distributed about the inside surface of the former, in some examples, it may be desirable for only a subset of the N conductive coils to be distributed about the inside surface of the former. The subset may comprise e.g. half of the N conductive coils, one or two thirds of the N conductive coils, 90 percent of the conductive coils, or 30 of 48 conductive coils. The subset of conductive coils may be any suitably sized subset of the N conductive coils.

When only a subset of the N conductive coils is distributed about the inside surface of the former, the conductive coils which do not form part of the subset may be distributed along a path leading into the former, or they may be distributed about an inside surface of a gate, as described in more detail below.

The method 100 further comprises a step 106 of reconfiguring the former from a first state to a second state to form a substantially circular coil pack. In the first state, the former is configured to permit the distribution of the N conductive coils without the overlapping portions of the first and the N ^th conductive coils overlapping, and in the second state, the former packs the N conductive coils such that the overlapping portions of each coil overlap the corresponding overlapping portions of respective adjacent coils to form a substantially circular coil pack.

For example, after the former is reconfigured from the first to the second state, the N conductive coils are packed such that overlapping portions of the first conductive coil overlap overlapping portions of the N ^th and second conductive coils, the overlapping portions of the second conductive coil overlap overlapping portions of the first and third conductive coils, and so on. The overlapping portions of the N ^th conductive coil overlap overlapping portions of the first and the N-1 ^th conductive coils. In this manner, the N conductive coils are packed to form a substantially circular coil pack.

It is noted that the terms “first” and “N ^th ” conductive coils do not necessarily refer to the order, either spatially or temporally, in which the conductive coils are provided or distributed.

The step 106 of reconfiguring the former from the first state to the second state to form the substantially circular coil pack may comprise moving at least one gate so as to close an opening in a circumference of the former. The N conductive coils may be provided to the former via the opening, and closing the opening by moving the gate packs the N conductive coils to form the coil pack.

Figure 2 illustrates a further example method 200 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 200 are identical to method 100, in particular steps 202 and 206 which are identical to steps 102 and 106. Method 200 further comprises a step 204 of distributing at least a subset of the N conductive coils about an inside surface of a former by conveying the N conductive coils along a predefined path.

It will be appreciated that at least a portion of the predefined path may follow the inside surface of the former, allowing for the distribution of at least a subset of the N conductive coils about the inside surface. As discussed above in relation to method 100, the N conductive coils are distributed such that the overlapping portions of the first conductive coil do not overlap respective overlapping portions of the N ^th conductive coil. The overlapping portions of any of the other of the N conductive coils may or may not be overlapping.

It is noted that at least a portion of the predefined path may be angled relative to an opening in the former, so as to allow for the coils to be easily provided, distributed, and packed to form the substantially circular coil pack.

Conveying the N conductive coils allows for the N conductive coils to be distributed evenly, i.e. for there to be an equal spacing or overlap between the N conductive coils, which facilitates packing to form the substantially circular coil pack.

Figure 3 illustrates a further example method 300 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 300 are identical to method 200, in particular steps 304 and 306 which are identical to steps 204 and 206. Method 300 further comprises a step 302 of providing N conductive coils by aligning the N conductive coils on a conveyor.

The N conductive coils are aligned on the conveyor in a line, such that the first of the N conductive coils overlaps the second of the N conductive coils, each of the second to N-1 ^th of the N conductive coils overlaps two respective adjacent conductive coils, and the N ^th of the N conductive coils overlaps the N-1 ^th of the N conductive coils. As such, as at least a subset of the N conductive coils are distributed about the inside surface of the former in step 304, providing the N conductive coils on a conveyor in a line allows for the subset to be evenly distributed, which again facilitates packing the N conductive coils to form the substantially circular coil pack.

Each, or at least some of, the N conductive coils comprises an attachment portion, and the conveyor comprises a continuous belt having recesses for attaching the attachment portions of the conductive coils, so that the conductive coils are releasably attached to the conveyor and provided in a line.

Figure 4 illustrates a further example method 400 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 400 are identical to method 100, in particular steps 404 and 406 are identical to steps 104 and 106. Method 400 further comprises a step 402 of providing N conductive coils in a line.

As set out above in relation to method 300, the N conductive coils are provided in a line.

However, in contrast to method 300, the N conductive coils are not conveyed to distribute at least a subset of the N conductive coils about an inside surface of the former, but are instead lifted and placed in the former to distribute 404 at least a subset of the coils about an inside surface of the former. Nevertheless, by providing the coils in a line, such that the first of the N conductive coils overlaps the second of the N conductive coils, each of the second to N-1 ^th of the N conductive coils overlaps two respective adjacent conductive coils, and the N ^th of the N conductive coils overlaps the N-1 ^th of the N conductive coils, distributing 404 and packing the conductive coils to form the substantially circular coil pack is facilitated.

If the N conductive coils are not conveyed and/or provided in a line, they may be provided by a hopper, a pick and place mechanism, or manually. At least a subset of the N conductive coils may be distributed about the inside surface of the former by the pick and place mechanism, or manually.

Figure 5 illustrates a further example method 500 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 500 are identical to method 100, in particular steps 502, 504, and 506 are identical to steps 102, 104, and 106. The substantially circular coil pack formed by the step 506 of reconfiguring the former from a first state to a second state comprises spaces for receiving flux guides.

The flux guides are in the form of lamination packs. The lamination pack is made up of grain oriented electrical steel sheets wrapped in insulation material.

The spaces are defined within each one of the N conductive coils and at the overlap between adjacent ones of the N conductive coils. As such, the substantially circular coil pack comprises more than one type of spaces, and these will be described in more detail below, with reference to Figures 10 to 13. The term “type of spaces” refers to a set of spaces having a substantially identical volume and/or shape. Different types of spaces are formed at different repeating positions about the circumference of the coil pack, e.g. one type of spaces is formed within each conductive coil, and another type of spaces is formed between overlapping, adjacent conductive coils.

If the substantially circular coil pack comprises more than one type of space, corresponding lamination packs may be provided for each type of space.

Method 500 further comprises a step 508 of aligning the N conductive coils such that each space for receiving a flux guide in the circular coil pack is substantially identical. Ensuring that the spaces are substantially identical facilitates insertion of flux guides, and allows for the insertion to be automated and for the simultaneous insertion of a plurality of flux guides.

As set out below, the coil pack, in these examples, comprises two different types of spaces, which may or may not overlap, and which may or may not be identical. As such, step 508 may refer to aligning the N conductive coils such that each space, or each space of the same type, is substantially identical.

A separate step 508 of aligning the N conductive coils is not necessary if the N conductive coils are already aligned, e.g. when distributing at least the subset of N conductive coils about the inside surface of the former is sufficient to ensure that the spaces of the coil pack are substantially identical. In an example in which the N conductive coils are provided by a pick and place mechanism, or using a cassette, or in a line, the N conductive coils are already positioned such that, upon packing them to form the coil pack, the spaces are substantially identical.

Method 600 illustrated in Figure 6 differs from method 500 only in that it includes a further step 610 of inserting flux guides into the (substantially identical) spaces.

Figure 7 illustrates a further example method 700 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 700 are identical to methods 500 and 600, in particular steps 702 to 708 which are identical to steps 502 to 508 and 602 to 608. Method 700 further comprises steps which distinguish between two methods of inserting flux guides into the spaces.

On the one hand, method 700 further comprises a step 712a of providing flux guides in a pattern corresponding to a pattern of spaces in the circular coil pack. In this example, the flux guides are attached to an electromagnet in the pattern.

Method 700 further comprises a step 714a of inserting the flux guides into the spaces, i.e. simultaneously inserting the flux guides, which were provided 712a in a pattern corresponding to the pattern of the spaces in the substantially circular coil pack. In this example, all of the flux guides are provided, and simultaneously inserted.

If not all of the flux guides are inserted simultaneously, method 700 can also comprise a step 712a of individually aligning and inserting a flux guide into a respective space.

Figure 8 illustrates a further example method 800 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 800 are identical to method 700, in particular steps 802 to 808, 812a, 812b, and 814a, which are identical to steps 702 to 708, 712a, 712b, and 714a. Method 800 further comprises optional steps which distinguish between methods of providing the flux guides for alignment, and insertion of the flux guides.

In particular, method 800 further comprises a step 809a of providing the flux guides to a cassette. The cassette has a plurality of cavities. Each cavity is configured to removably receive one of the plurality of flux guides. The plurality of cavities is provided in a pattern which substantially corresponds to the pattern of spaces in the circular coil pack. As such, the flux guides in the cavities in the cassette are already align with the spaces in the coil pack, such that the flux guides are aligned, and inserted, into the spaces more easily.

As step 812b requires individual aligning and inserting of flux guides, this step cannot be combined with step 809a, unless a subset of the flux guides is provided in a pattern and simultaneously inserted, while another subset of flux guides is individually aligned and inserted.

Where at least some of the flux guides are provided to a cassette, they are provided and inserted into the spaces (steps 812a and 814a) directly from the cassette.

Method 800 further comprises a step 810 of attaching the, or each, flux guide to an electromagnet. The plurality of flux guides are attached to the electromagnet in a pattern which substantially corresponds to the pattern of spaces in the substantially circular coil pack. This allows for the flux guides to be easily inserted into the spaces (according to steps 812a and 814a).

Similarly, if a single flux guide is attached to the electromagnet, it is provided in a position corresponding to a respective space in the substantially circular coil pack.

Where the steps 809a and 810 are combined, (at least some of) the flux guides are provided in a pattern to a cassette, an electromagnet engages the flux guides, and said electromagnet provides and inserts the flux guides into respective spaces. The flux guides are provided 809a to the cassette by hand.

The flux guides are be attached 810 to the electromagnet from a cassette. As described above regarding the cassette, in this example, the electromagnet is rotated, so that a hopper or a pick and place mechanism provides each flux guide to the same position, while the electromagnet is rotated so as to allow the flux guides to be provided in the pattern.

In another example, the flux guides are attached to the electromagnet using a pneumatic device, similar to a nail gun, that moves the flux guides to attach them to the electromagnet. Again, the electromagnet is rotated if required, or the pneumatic device is movable by attaching the pneumatic device to a rotating carousel.

Figure 9 illustrate a further example method 900 of forming a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Some steps of method 900 are identical to method 800, in particular steps 902 to 910, which are identical to steps 802 to 810. Method 900 further comprises steps of attaching locating guides to the flux guides, as set out below.

Method 900 further comprises a step 913a of attaching a locating guide to each flux guide. The locating guides are configured to facilitate insertion of the flux guides into the spaces in the substantially circular coil pack.

Each locating guide comprises a shaped tip for locating a respective one of the spaces. The shaped tip is rounded so as to reduce any risk of damage to the coil pack.

As described below, the locating guide is ferromagnetic, so that they are engageable by an electromagnet.

While method 900 comprises an optional step 908 of aligning the N conductive coils such that each space for receiving a flux guide in the circular coil pack is substantially identical, the locating guides are configured to perform the step of aligning the N conductive coils such that each space for receiving a flux guide is substantially identical. That is, the shaped tip is configured to locate the spaces, and the remaining portion of the locating guides is configured to align the N conductive coils. As such, in this example, the step 908 of aligning is unnecessary.

In method 900, if all of, or some of, the flux guides are inserted individually, method 900 further comprise the step 912b of individually aligning a flux guide with a respective space, the step 913b of attaching a locating guide to the flux guide, and the step 914b of inserting the flux guide into the respective space. The locating guide are attached 913b to the flux guide before the flux guide is aligned 912b.

The steps 912b to 914b are repeated until all of the flux guides have been inserted, e.g. until each of the spaces has been filled.

Each step of any of the method 100 to 900 may be combined with one or more steps of the other methods, unless any of the steps are mutually exclusive. For example, steps 912b to 914b may be combined with method 100. Any of the above methods 100 to 900 may further comprise a step of placing the substantially circular coil pack in a stator housing. Any method of the present disclosure that includes inserting flux guides into the spaces in the coil pack may further comprise transferring the coil pack using an electromagnet, the electromagnet engaging with the flux guides.

Any of the above methods 100 to 900 optionally comprises a step of providing at least one guide for aligning the coil pack and the stator housing. The at least one guide is a separate component to the stator housing. The at least one guide is configured to be introduced into the path of the coil pack. The guide is configured to align the coil pack with the stator housing, and is configured to be removed after alignment. The at least one guide is a shaped metal guide.

Any of the above methods 100 to 900 optionally further comprises a step of providing and connecting at least one busbar to the circular coil pack.

Figures 10A-10B are various views of an exemplary conductive element 120. Each of the N conductive coils is made up of one or more conductive elements 120. It will be appreciated that in the case of one conductive element 120 per conductive coil, a conductive coil and a conductive element 120 are equivalent. Figures 12A-12B illustrate a conductive coil 12 which is made up of two conductive elements 120 and 120’, and will be described below.

Returning to Figures 10A-10B, as is best appreciated from the top-down views of Figure 10A in which the axis of rotation is perpendicular to the plane of the page, a conductive element 120 includes a pair of circumferentially pitched apart, radially extending active conducting sections 121a, 121 b. These radially extending active sections 121a, 121 b are referred to as “active” sections because, when the conductive coils 12 are positioned in a stator, they are disposed within a stator core and so interact with a magnetic field provided by magnets of rotors. It will be appreciated that since the active sections extend in a generally radial direction, which is approximately perpendicular to the axial flux in the core, the flux linkage is at least close to maximized.

The angle y by which the two active sections 121 a, 121 b are pitched apart will be referred to as the coil span. The coil span can be the same as or different (less or more) than a pole pitch a (defined by the angle between the centres of the permanent magnets of the rotor). Turning to Figures 11A and 11 B, these show a sixteen-pole, three-phase coil pack 10’. In Figures 11A and 11 B, a conductive coil 12 and a conductive element 120 are equivalent. Conductive coils 120a, 120b, 120c of coil pack 10’ are circumferentially distributed around the coil pack and circumferentially adjacent conductive coils circumferentially overlap.

As is particularly clear from Figure 11 A, the circumferential overlap of the coils 120a, 120b, 120c defines circumferential spaces between active sections of the coils. These circumferential spaces, which are elongated in the radial direction, can receive the flux guides 30, as set out in relation to methods 500, 600, 700, 800, and 900 above. Spaces such as the labelled spaces 141a, 141 b, 141 c will be referred to as spaces of a first type. As can be seen, spaces of the first type 141a, 141 b, 141c are defined between active sections of different coils. For example, space 141 b is between one of the two active sections of coil 120a and one of two active sections of coil 120c. However, it is to be appreciated that the two coils that define a particular space of the first type 141a, 141 b, 141c can depend on various factors, including the number of phases per stator pole, the number of poles and the selected coil span y. As such, while in this example, the space 141 b is between active sections of coils which are not immediately adjacent (i.e. coils 120a and 120c), the spaces in other examples may be between immediately adjacent coils (such as coils 120a and 120b).

As can be seen from Figure 10B, the two active sections 121a, 121 b are axially offset from each other. This facilitates stacking, or overlapping, of the conductive coils in the circumferential direction, and also facilitates the circumferential stacking, or overlapping of conductive elements 120 where there are multiple conductive elements 120 per conductive coil. This allows for more stator poles and more slots per pole per phase, both of which can provide for greater efficiency. Furthermore, the winding may be readily short chorded.

As can be seen in Figure 10B, each conductive element 120 is formed from a continuous length of wound conductor. The outermost winding of the length of conductor terminates at a first connection portion 128, which will be referred to as the outer tail 128. The outer tail 128 extends substantially parallel to the axial direction. As will be described in more detail below, this facilitates convenient connection of the coils 12 to the multi-phase power supply. The innermost winding turn portion terminates at a second connection portion 129, which will be referred to as the inner tail 129.

The outer tail 128 in this example is further used to connect the conductive element 120 to the conveyor, e.g. to a hole of the conveyor. That is, the outer tail 128 is the attachment portion of the conductive coil.

As can also be seen in 10B, the length of conductor that forms the conductive element 120 is wound such that there are a plurality of winding turn portions 131a, 131 b stacked parallel to the axis of rotation of an electrical machine. The resulting cross-section of the conductive element 120 that is perpendicular to the radial direction of each active section 121a, 121 b is elongate with a major dimension parallel to the axis of rotation. In the example of Figures 10A-10B, there are fourteen axially stacked winding turn portions 131 a, 131 b, though the conductive elements 120 may equally have any other number of turn portions 131a, 131 b.

As can be seen from Figure 10B, the outer first portions 123 together form an outer part 133 of the coil element 120 with a surface that is substantially parallel to the axis of rotation. In the specific example of Figures 10A-10B, the outer first portions 123 are substantially semi-circular and so the outer part 133 is a substantially flat half-disk 133, but other shapes are possible. For example, each of the outer first portions 123 may have a shape corresponding to three sides of a rectangle, such that they together form an outer part 133 which has a flat rectangular surface. As another example, the outer part 133 of the conductive element 120 formed by the outer first portions 123 need not be flat or planar, it may have a curved profile and therefore curved surface.

As noted above, each conductive coil may include only one conductive element 120. However, for reasons which will be explained in more detail below, each conductive element preferably includes two or more circumferentially overlapping conductive elements. An example of a conductive coil that includes two circumferentially overlapping conductive elements 120, 120’ will now be described with reference to Figures 12A-12B.

Figure 12A shows above and below views of a conductive coil 12 which includes two conductive elements 120, 120’. The features of each of the two conductive elements 120, 120’ are the same as those of the single conductive element 120 described above with reference to Figures 10A- 10B, and so their features will not be described again.

To form the conductive coil 12, two identical conductive elements 120, 120’ are electrically connected together in series at their inner tails 129, 129’. In the examples illustrated herein, the inner tails 129, 129’ are connected using a ferrule 130. However, there are other ways of connecting the inner tails 129, 129’, such as brazing or welding. To connect the two elements 120, 120’, one of the two conductive elements 120, 120’ is rotated 180° about the axis running vertically in the plane of the page in Figure 12A so that the outer tails 128, 128’ of the two conductive elements 120, 120’ are in opposite directions and the inner tails 129, 129’ are adjacent and therefore readily connected by a ferrule 130. Alternatively, the conductive coil 12 comprising two conductive elements could be integrally formed as a single piece.

The resulting conductive coil 12 has two pairs of circumferentially overlapping, pitched apart pairs of active sections 121a, 121 b; 121 a’, 121 b’. Notably, the overlap of the two pairs of active sections defines two spaces 142a, 142b. The first space 142a is defined between one (a first) active section 121a of a first of the conductive elements 120 of the coil 12 and between one (a first) active section 121a’ of the second of the conductive elements 120’ of the coil 12. The second space 142b is defined between the other (the second) active section 121 b of the first conductive element 120 of the coil 12 and between the other (the second) active section 121 b’ of the second conductive element 120’ of the coil 12. That is, the two spaces 142a, 142b are circumferential spaces between adjacent active sections 121a, 121a’; 121 b, 121 b’ of two different pairs of active sections 121 a, 121 b; 121a’, 121 b’ of the same coil 12. Spaces of this type will be referred to as spaces of a second type. Like the spaces of the first type, spaces of the second type 142a, 142b provide spaces for flux guides 30, such as lamination packs. This makes it easier to construct a stator, and also increases the number of slots per pole per phase of the stator, which can increase the motor’s efficiency. Having now described spaces 141a-c of the first type (that is, spaces defined between active sections of different coils) and spaces 142a-b of the second type (that is, spaces defined between active sections of the same coil but different pairs), it is noted that when a plurality of coils 12 which define spaces of the second type are provided in a coil pack 10 so as to define spaces of the first type, the spaces of the first and second types may coincide. Whether spaces of the first and second type coincide may depend on a number of factors, including the selected coil span y, the number of stator poles and the number of phases. It is noted that where the spaces are referred to in relation to the methods above as being “substantially identical”, this may refer to spaces of one of the types only, or to spaces of each type of space. That is, if a coil pack comprises spaces of a first type and spaces of a second type, the spaces of the first and second types may differ, whereas each space of the first type is identical, and each space of the second type is identical.

Returning to Figures 12A-12B, it can also be seen that there is a gap 143a between the second portions 124a, 124a’ of the outer loop sections 122, 122’ which form one pair of outer involute parts 134a, 134a’ of the two conductive elements 120, 120’. Likewise, there is a gap 143b between the second portions 124b, 124b’ of the outer loop sections 122, 122’ which form the other pair of outer involute parts 134b, 134b’. There is also a gap 144a between the second portions 127a, 127a’ of the inner loop sections 125, 125’ which form one pair of inner involute parts 137a, 137a’. Finally, there is also a gap 144b between the second portions 127b, 127b’ of the inner loop sections 125, 125’ which form the other pair of outer involute parts 137b, 137b’. Due to the geometric properties of involutes, the width of these gaps 143a, 143b, 144a, 144b remains substantially constant along the length of the involute sections of the conductive elements 120, 120’. This advantageously reduces the resulting diameter of the motor for a given rating and losses in the coils.

Now turning to Figure 13, the conductive components 10 are shown without a stator housing or flux guides. Each conductive coil 12 is connected to one phase of a multi-phase power supply via connection means 15, 16 which in this example take the form of busbars. In this specific example, the conductive components 10 are configured for use with a three-phase power supply so there are three conductive coils 12 per pole of a stator.

It will be appreciated that with sixteen poles and three conductive coils 12 per pole, the conductive components 10 of Figure 13 have a total of 48 circumferentially distributed conductive coils 12. The conductive components 10 actually have 96 radially extending active sections. In this example of the conductive components of a stator, each conductive coil 12 includes one or more conductive elements 120, each of which includes a pair of axially offset radially extending active sections. Each conductive coil 12 shown in Figures 12A and 12B includes two such conductive elements 120, and since each conductive element 120 includes a pair of axially offset radially extending sections, there would be a total of 192 radially extending active sections. In the particular arrangement of Figure 13, the conductive components 10 are connectable by a parallel connection arrangement, in which each of the connection means 15, 16 includes three phase-connections and one star-connection. That is, the first connection means 15 includes a first phase connection 151 for a first phase of the power supply, a second phase connection 152 for a second phase of the power supply, a third phase connection 153 for a third phase of the power supply, and a star connection 154. Similarly, the second connection means 16 includes a first phase connection 161 for the first phase of the power supply, a second phase connection 162 for the second phase of the power supply, a third phase connection 163 for the third phase of the power supply, and a star connection 164.

In the described examples, the phase connections 151-153, 161-163 and star connections 154, 164 are in the form of annular busbars whose outer circumference (though equally this could be the inner circumference) substantially coincides with the axially extending outer tails 128, 128’ of the conductive coils. The phase connection busbars 151-153, 161-163 are themselves connected to the power supply via inputs 1510-1530, 1610-1630.

Figure 14 illustrates an example method 1400 for inserting flux guides into a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Method 1400 comprises a step 1402 of providing a substantially circular coil pack. Providing 1402 a substantially circular coil pack may include any of the steps of methods 100 to 500.

Method 1400 further comprises a step 1404 of attaching a plurality of flux guides to an electromagnet in a pattern corresponding to spaces in the coil pack. As set out in relation to method 800, the flux guides are attached to the electromagnet in the pattern using a pneumatic device, similar to a nail gun, that moves the flux guides to attach them to the electromagnet. The electromagnet is rotated if required, or the pneumatic device is moved by attaching it to a rotating carousel containing the flux guides.

Method 1400 further comprises a step 1406 of aligning the electromagnet and the coil pack so that spaces in the coil pack and the flux guides, which are attached to the electromagnet, are aligned with one another; and a step 1408 of moving at least one of the electromagnet and the coil pack relative to one another, so as to insert the flux guides into the coil pack.

Method 1400 may further comprise any of the steps as set out above in methods 100 to 900, such as providing locating guides to facilitate insertion of the flux guides into the spaces.

Figure 15 illustrates a further example method 1500 for inserting flux guides into a coil pack for a stator of a radial flux electrical machine embodying the present disclosure. Providing 1502 a substantially circular coil pack includes any of the steps of methods 100 to 500. Method 1500 further comprises a step 1504 of placing a plurality of flux guides into a cassette comprising a plurality of cavities, each cavity configured to removably receive one of the flux guides. Method 1500 further comprises a step 1506 of aligning the cassette and the coil pack so that the spaces and the flux guides are aligned with one another, and a step 1508 of moving at least one of the cassette and the coil pack relative to one another, so as to insert the flux guides into the spaces.

Figure 16A shows plan views of a coil pack 1600 in a former (not shown) before and after reconfiguration of the former from the first to the second state. In this example, the former comprises two gates, so that the coil pack 1600, before the former is reconfigured by closing the gates, has three “sets” of conductive coils as shown on the left in Figure 16A: a first set 1602 of the conductive coils is already aligned in a substantially semi-circular shape. A second set 1604 and a third set 1606 of the conductive coils are separated, circumferentially, by a gap 1608. In this way, the overlapping portions 1604A and 1606A of the conductive coils closest to the gap 1608 do not overlap. However, the overlapping portions 1604A and 1606A are arranged so as to overlap upon the former being reconfigured from the first to the second state, as shown in Figure 16B on the left. The coils of the second set 1604 and the third set 1606 of conductive coils are provided at an angle 0 relative to the circular shape of the first set 1602 of the conductive coils.

The right hand side of Figures 16A and 16B shows the coil pack 1600 after the former has been reconfigured from the first to the second state to form the substantially circular coil pack 1610 in which the overlapping portions of each of the conductive coils overlap the overlapping portions of adjacent conductive coils. This is achieved by pushing the second set 1604 and third set 1606 of conductive coils towards one another to reduce the angle relative to the circular shape of the first set 1602 of the conductive coils, and to close the gap 1608 by overlapping the corresponding overlapping portions 1604A and 1606A.

Figure 17A shows a schematic of an example former 1700. Former 1700 comprises a static portion 1702 having a substantially (part-)circular inner surface 1703. Movably attached to the static portion 1702 of the former 1700 is a gate 1706 configured to close the opening 1707 in the circumference of the former 1700, the opening 1707 being present when the former 1700 is in the first, “receiving”, state. In the first, or “receiving”, state, the former 1700 is configured to receive N conductive coils.

The gate 1706 in this example is made up of a plurality of gate elements 1708a, 1708b, 1708c, and 1708d. The gate 1706 is made up of any number of gate elements, i.e. it may comprise only a single gate element, or a larger number of gate elements. The gate 1706, as shown in Figure 17A, is attached to the static portion 1702 by an articulated joint 1710a. The various gate elements 1708a, 1708b, 1708c, 1708d are attached to one another by articulated joints 1710b, 1710c, 1710d.

Figure 17B shows a schematic of another example former 1750, comprising a static portion 1752 and a gate 1756. The gate 1756 is pivotably attached to the static portion 1752 of the former 1750 by a pivot 1754 which comprises a pivot pin 1755. As shown, this example former 1750 comprises aligning elements in the form of projection 1758 which protrude from the inside surface of the former. The projections 1758 are configured to align the conductive coils before and/or upon the gate 1756 being closed. Closing the gate 1756 is equivalent to reconfiguring the former 1750 from the first state shown in Figure 17B to a second, closed, state (not shown). The gate 1756 has an inner surface 1757 which is shaped so that, when the gate 1756 is closed, the inner surface 1757 of the gate 1756 aligns with an inner surface 1753 of the static portion 1752 so as to pack the conductive coils in the substantially circular shape.

Figure 18A shows a schematic of another example former 1800, which is substantially similar to former 1700, and comprises a static portion 1802 having a substantially (part-)circular inner surface 1803. Movably attached to the static portion 1802 of the former 1800 is a gate 1806 configured to, at least partially, close the opening 1807 in the circumference of the former 1800.

The gate 1806 is made up of a plurality of gate elements 1808a, 1808b, 1808c, and 1808d and is attached to the static portion 1802 by an articulated joint 1810a.

Former 1800 differs from former 1700 in that it comprises a second gate 1814 which is pivotably attached by a pivot 1812 to the static portion 1802, at the opposite end of the static portion 1802 to gate 1806. The gate 1806 and the second gate 1814 cooperate to close the opening 1807 as the former 1800 is reconfigured from the first state, in which the former 1800 is configured to receive N conductive coils, to a second state.

As shown in Figure 18B by way of another example former 1850, the former 1850 comprises a conveyor 1852, representing the path along which N conductive coils are conveyed so as to distribute (at least a subset of) the N conductive coils along an inside surface of the former 1850. The N conductive coils in this embodiment are reversibly attached to holes in the continuous belt which forms the conveyor 1852.

A first portion 1856 of former 1850 is a static portion, with a second portion 1858 acting as a gate which is movable relative to the static portion 1856 about pivot 1854. However, in alternative examples, both the first and second portions 1856 and 1858 are movable relative to one another, in a “pincer” like movement, about pivot 1854. Figure 18C shows an example of a flux guide. The flux guide is a lamination pack 1880 configured to be placed into one of the spaces formed within, or between, conductive coils. Attached to the lamination pack 1880 is a locating guide 1882 having a tip 1884 for locating a corresponding space.

On the left hand side, Figure 19 shows a further example former 1900. Former 1900 comprises two parts 1902 and 1904, each having a semi-circular shape comprising retractable coil retaining pins 1906 arranged to receive coils 1908 for forming a coil pack. Figure 19 shows only a portion of the conductive coils 1908 assembled into the former 1900, retained by the coil retaining pins 1906 of one of the two parts 1902. The final two retaining pins 1907 of each of the parts 1902 and 1904 are only half the length of the remaining retaining pins 1906 so as to allow the “half stators” of coils 1908 when assembled onto the retaining pins 1906 in each part 1902 and 1904 to overlap upon reconfiguration of the former 1900.

Figure 20 shows the former 1900, once all coils 1908 have been assembled into the two parts 1902 and 1904.

The former 1900 further comprises a handle attached to a tensioning means 1910. Actuation of the handle actuates the tensioning means 1910, causing the two parts 1902 and 1904 to move towards each other to overlap the ends of the two “half stators”, binding them together. As such, the tensioning means 1910 is configured to rearrange the stator from the first state, shown in Figures 19 and 20, to the second state, shown in Figures 21 A and 21 B, in which the two parts 1902 and 1904 are immediately adjacent one another.

Figure 19 further shows a stator housing 1912, and a stator clamp 1914 arranged on a rail 1916, allowing for a formed stator to be moved from the former 1900 to the stator housing 1912.

Figures 21 A and 21 B show the former in the second state, i.e. with the coils of the two “half stators” overlapping. However, for ease of reference, in Figures 21 A and 21 B, the coils 1908 have been omitted. As is shown in Figure 21 B, the base plate 2100 of the former 1900 comprises slots through which the retaining pins 1906 extend, allowing for the retaining pins 1906 to be retracted once the coil pack/stator has been formed.

The retaining pins 1906 are provided to occupy only every second space of an assembled coil pack, so that flux guides/lamination packs may be introduced into every second space before the retaining pins 1906 are retracted. Once the retaining pins 1906 are retracted, the remaining flux guides may be introduced in the, now unoccupied, spaces. This ensures stability of the assembled coil pack/stator during assembly.

As best seen in Figure 19, the inner surface of the stator housing 1912 comprises a plurality of fingers 1920 configured to engage with the radially outward ends of the coils 1908 of the assembled stator. As shown in Figure 22, the assembled stator 2200 is engaged by an electromagnet of the clamp 1914 to lift the stator 2200 out of the former 1900. The clamp 1914 is configured to slide along the rail 1916 to move the assembled stator 2200 into the stator housing 1912.

A guide 2202 is held above the stator housing 1912 by clamps 2204 to allow the assembled stator 2200 to be introduced into the stator housing 1912 more easily and without damaging the stator 2200.

Attached to the guide 2202, but not visible in the drawings, are flexible inserts, made of Nomex™, which are configured to deform over sharp edges of the stator housing upon insertion of the stator into the stator housing, so as to prevent scratching of the stator.

Figure 23 shows the assembled stator 2200 in the stator housing 1912, the guide 2202 having been removed following loosening of clamps 2204.

As discussed above, the inner surface of the stator housing 1912 comprises fingers 1920, which when the assembled stator 2200 is in the housing 1912, interdigitate the radially outward ends of the coils 1908 of the stator 2200. The inventors have found that there is a risk of damage, e.g. by scratching, to the stator 2200, even when a guide 2202 and inserts are provided.

Therefore, some, or preferably all, of the fingers may be provided with a cover 2400 as shown in Figures 24A and 24B, which has a generally “M” or “W” shape. The cover 2400 comprises a first, central, slot 2402, sized to be clipped onto one of the fingers 1920, and two second, outside, slots 2404, arranged so as to receive radially outward ends of a pair of coils 1908 of the stator 2200.

A further example former is described below, most features of which are similar to former 1900. The further example former also has two semi-circular parts. Provided with the further example former is a robotic manipulator, configured to individually pick the N conductive coils and individually place the N conductive coils in the former, so that they are distributed about an inside surface of the former.

The further example former has a circular, rotatable base, configured to rotate after each time one of the N conductive coils is placed in the former, so that the robotic manipulator may place each of the N conductive coils in a same position, while rotation of the rotatable base allows for the coils to be placed in substantially semi-circular patterns.

The further example former comprises a pin, configured to rotate together with the rotatable base, which is configured to hold the already distributed coils in place, so that they do not disengage from one another and remain aligned. Once the N conductive coils have been placed in the further example former, a linear actuator causes movement of the two semi-circular parts towards one another to overlap the ends of the two “half stators”, binding them together to form a substantially circular coil pack having spaces, as set out above in relation to former 1900.

The further example former further comprises a shuttle, configured to reciprocally move to collect a flux guide, insert it into one of the spaces, permit the rotatable base to rotate to the next space, move back into the collection position to collect a flux guide, and insert it into the adjacent one of the spaces, until flux guides have been inserted into each of the spaces.

The further example former further comprises means for sandwiching the circular coil pack with inserted flux guides. The further example former further comprises means for moving the coil pack horizontally towards a stator housing to align the coil pack with the stator housing. The coil pack may be sandwiched prior to, or after, horizontally aligning the stator housing. Sandwiching may facilitate the final (vertical) insertion of the coil pack into the stator housing.

The further example former further comprises guides for guiding the circular coil pack into the stator housing, to prevent damage to the coils of the circular coil pack and ensure correct alignment of the coil pack with the stator housing.

One advantage of the further example former may be that it allows for fully automated forming of a stator.