GB2604033A

GB2604033A - Electric machine stator core

Info

Publication number: GB2604033A
Application number: GB2201424.5A
Authority: GB
Inventors: Conway Ash Lloyd
Original assignee: Electrified Automation Ltd
Current assignee: Electrified Automation Ltd
Priority date: 2021-02-19
Filing date: 2022-02-03
Publication date: 2022-08-24
Anticipated expiration: 2042-02-03
Also published as: GB202202288D0; GB2604042A; GB202102697D0; GB2603926B; GB2603969A; GB2604034A; GB2604033B; GB2603969B; GB2603926A; GB2604034B; GB202102330D0

Abstract

A stator core 110 comprising an articulated array of core segments 120 each segment being hinged 130 connected to at least one adjacent segment such that the core has a first configuration in which the segments form an open array and a second configuration in which the segments form a closed annular array. Each segment has an L-shaped profile comprising a body defining a segment of an annular ring; and a pole tooth 150 projecting radially from the annular ring segment; and where the body comprises first and second complementary interface surfaces at respective circumferentially opposing sides of the body and one of the interface surfaces extends through a circumferential footprint F of the pole tooth. First and second complementary interface surfaces of adjacent core segments may abut when the core is in a closed configuration, and the surface may extend through the entire circumferential extent of the footprint of the tooth, where the surface may extend at an oblique angle through the body. The segment may comprise a flange at the foot of the pole tooth and interface surface extending through the footprint of the tooth. A hinge connection comprising a web may be provided between adjacent first and second complementary interface surfaces. An inter-engagement feature may radially align adjacent segments in the closed position.

Description

ELECTRIC MACHINE STATOR CORE

Field of Invention

The present invention relates to stator core assemblies, stators, electric machines and methods of assembly associated therewith.

Background

Electric machines (which it will be appreciated is used as a general term for a machine which uses electromagnetic forces such as an electric motor or generator) may consist of a stator and a rotor and operate through the interaction of the machines magnetic field.

A common stator configuration comprises a laminated body (which may, for example, be stamped from steel) defining a generally annular body with a plurality of radially extending pole teeth. Each pole tooth is surrounded by an electrical winding in the assembled electric machine. Manufacturing cost is a key consideration in the design of electrical machines and as such a number of different stator assembly methods have been proposed. In some arrangements the stator core may be divided into a number of stator core segments which come together to form the full annular stator core lamination. Each core segment comprises a part of the annular body and a single pole tooth. One advantage of such segmented stator cores is that they can simplify the winding process since the winding may be positioned around each stator pole to assembly of the full stator. In other designs, such as that shown in European Patent Application EP 0 871 282 Al, the individual stator core segments are linked together by flexible portions such that the stator core has an open configuration in which the segments form an open or linear array and a closed configuration in which the segments form an annular array. To aid manufacture the stator of EP 0 871 282 Al also includes pole teeth having tooth tip which are initially radially projecting to allow each of placement of a bobbin carrying the windings onto the pole tooth. Once the bobbin is in place the tooth tips are pressed to form a profile having generally sideways/circumferential extending tooth tips.

There remains a desire to provide further improvements in the ease of manufacture of electric machines and stators and rotors for electric machines. For example, it is desirable to assemblies for electric machines, including rotors and/or stators with a reduced part count and which may be suitable for automated assembly.

Summary of Invention

According to one aspect of the invention, there is provided a stator core comprising an articulated array of core segments each segment being hingedly connected to at least one adjacent core segment such that the core has a first configuration in which the core segments form an open array and a second configuration in which the core segments form a closed annular array. Each core segment has an L-shaped profile comprising: a body defining a segment of an annular ring; and pole tooth projecting radially from the annular ring segment. The body comprises first and second complementary interface surfaces at respective circumferentially opposing sides. One of the interface surfaces extends through a circumferential footprint of the pole tooth.

The applicant has recognised that the use of an L-shaped segment (which results in a join line between adjacent segments in the footprint of the pole tooth) provides both structural and magnetic field advantages in the final stator. As such embodiments may provide a stator which is more optimised than conventional T-shaped segmented stators.

It may be appreciated that the footprint of the pole tooth is the portion of the body which is between the circumferentially opposing sides of the pole tooth. The footprint may be radially outside or radially inside of the pole tooth (depending upon whether the stator is of the type having an external stator core and radially inwardly projecting pole teeth or the type having an internal annular stator core with outwardly projecting pole teeth).

Adjacent first and second complementary interface surfaces of adjacent core segments may abut when the stator core is in a closed configuration and may be spaced apart when the stator core is in the open configuration.

The interface surface extending through the circumferential footprint of the pole tooth may extend through substantially the entire circumferential extent of the footprint of the pole tooth. In embodiments the interface surface extending through the circumferential footprint of the pole tooth may be an inclined surface extending through a footprint of the pole tooth. In some embodiments the interface surface extending through the circumferential footprint of the pole tooth may extend at an oblique angle through the body. The angle may be oblique relative to the radial direction. As such, the interface surface may be a tapered surface extending through the thickness of the body.

The interface surface extending through the circumferential footprint of the pole tooth may extend circumferentially beyond the pole tooth. For example, the core segment may comprise a flange at the foot of the pole tooth (the flange may extend circumferentially away from the pole tooth). The interface surface extending through the circumferential footprint of the pole tooth may extend from the flange through the footprint of the pole tooth. The interface surface may, therefore, start at one side of the pole tooth, extend through the circumferential footprint and end on the other side of the pole tooth.

A hinge connection may be provided between adjacent first and second complementary interface surfaces of adjoining core segments. The interface surface extending through the circumferential footprint of the pole tooth may extend from a first end radially proximal to the pole tooth to a second end radially distal to the pole tooth. In some embodiments, for example, the first end may be at the flange at the foot of the pole tooth. The hinge connection may be at the second end of the first interface segment.

The hinge connection may comprise a web. The web may provide a living hinge between adjoining core segments. The web may be elongate, for example circumferentially elongate. The web may, for example, extend at least partially along a portion of one of the segments. For example the web may be separated from the segment by a generally circumferentially aligned slot. The web may further provide a resilient connection between the adjoining core segments, the web may bias the core segments towards the open position. For example, the web may act as a leaf spring.

Advantageously, the provision of a web as a hinge between adjacent core segments helps to avoid or reduce stress concentrations that might occur at the hinge. For example the bending of the material of the hinge can be progressive and spread along the length of the web. This is important in reducing or removing the risk of failure of the hinge in either manufacture or use. The reduced risk of failure at the hinge also ensures that the hinge can be safely formed as an integral part of the stator laminations and does not for example need to be a separate component formed from a more pliable material.

The first and second complementary interface surfaces may comprise at least one inter-engagement feature. The inter-engagement feature may for example comprise a male feature on one of the first and second complementary interface surfaces and a complementary female feature on the other of the first and second complementary interface surfaces. The inter-engagement feature may provide a positive location when the surfaces are brought together. The inter-engagement feature may radially align adjacent segments in the closed position.

When the stator is in the closed configuration the web may provide a tensile force which acts to hold the inter-engagement feature in alignment. For example, the web may provide a radial and/or circumferential bias at the complementary interface surfaces of adjacent segments. The inter-engagement feature may hold the adjacent segments in alignment against said bias. In other words, the spring force of the web may provide a positive engagement between the inter-engagement features when the stator is in the closed/annular configuration.

To provide an open configuration the array of articulated core segments may comprise first and second end segments which are hingedly connected to only one adjacent core segment. As may be appreciated, the end segments may be at opposite ends of the stator array. The core segments intermediate to the end segments may each be hingedly connected to a pair of adjacent core segments. For example, the intermediate segments may each include a first complementary interface surface hingedly connected to the second interface surface of one adjoining core segment and a second complementary interface surface (at the opposing circumferential side of the segment body) hingedly connected to the first interface surface of another adjoining core segment.

The first end segment may comprise a first end face and the second end segment may comprise a second end face. When the stator core is in the open configuration the first and second end faces may be at opposing free ends of the array. When the stator core is in the closed annular configuration first and second end faces may abut. The end faces may be provided with complementary engagement features. The complementary engagement features may resiliently engage to hold the stator core in the closed annular array configuration. One of the end faces may be provided with a latch to engage a corresponding feature on the other end face. The latch may be configured to engage an arm extending from the opposing end face. The latch may comprise a generally circumferentially extending arm and a generally radially aligned head (the head may define a radially extending latch face).

In some embodiments the (or each) pole tooth may comprising a pair of tooth tips which have an initial configuration in which they extend longitudinally with respect to the pole tooth and an assembled configuration in which they extend transversely to provide a flange at the pole tooth end. Each tooth tip may comprise a web contiguous with the pole tooth and a head at the distal end of the web. The pole tooth may have a recess in the shoulder proximal to each tooth tip the recess defining a seat to receiving and aligning a portion of the head when the tooth tip is in assembled configuration.

The stator core segment may further comprise a bobbin carrying a coil. The bobbin is formed of an insulating material, for example from a moulded plastic. The bobbin may be positioned over the pole tooth prior to the tooth tips being deformed to their transverse position. For example, the bobbin may be slid onto the pole tooth in the longitudinal direction. The bobbin may engage the second portion of the head of the tooth tip when the tip is in the assembled configuration. For example, the bobbin may resiliently engage the distal end of the tooth tip. Thus, in some embodiments both the distal and proximal ends of the tooth tip may be engaged when in the assembled position.

A further aspect of the invention comprises a method of assembling a stator, the method comprising the steps of: providing a stator core comprising an articulated array of pole teeth in an open linear configuration; providing a coil winding on each pole tooth; rolling the stator core into a closed annular array; wherein rolling the stator core into a closed array comprises hinging interface surfaces formed in the footprint of each pole tooth into engagement.

A further aspect of the invention comprises a method of assembling a stator, the method comprising the steps of: providing a stator core comprising an articulated array of pole teeth in an open linear configuration; providing a coil winding on each pole tooth; rolling the stator core into a closed annular array; wherein rolling the stator core into a closed array comprises bringing opposing free ends of the stator core into abutment and engaging complementary engagement features provided on the ends to latch the stator core in a closed annular configuration.

The method may be used in conjunction with the embodiments described above.

Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description or drawings.

Description of the Drawings

Embodiments of the invention may be performed in various ways, and embodiments thereof will now be described by way of example only, reference being made to the accompanying drawings, in which: Figure 1A and 16 show an electrical machine in accordance with an embodiment; Figures 2 shows an end view of the stator core in a closed configuration in accordance with an embodiment; Figure 3 shows a views of the stator core of figure 2 in an open configuration; Figure 4 shows a detailed view of the stator core hinge interface of figure 2; Figure 5 shows a detail of the latching detail of the stator core of figure 2; Figures 6A to 6C illustrates the method of assembling a stator in accordance with an embodiment;

Detail Description of Embodiments

It may be noted that directional/orientational terms such as radial, circumferential and axial may be used herein to refer to the general directions of the assembly or components thereof relative to their in-use configuration. The general directions are shown, by way of example only, by arrow R showing a radial direction, C showing a circumferential direction and A showing an axial direction in Figure 1. However, the skilled person will appreciate that (unless expressly indicated otherwise) such directions are used broadly and do not imply strict mathematical conformance with a particular orientation. Likewise, the use of such terminology does not exclude a component or feature having a non-circular or irregular form.

An electric machine 1 is shown in figure 1A and comprises a stator 100 surrounding a rotor 200. The stator comprises a stator core 110 and a plurality of coils 300 mounted on poles of the stator core 110 Figure 1B shows the rotor 200 and stator 100 in an exploded configuration.

The stator core 110 in accordance with an embodiment is shown in figure 2. As will be known in the art, the stator core 110 may be formed from metal laminations which are stamped into the required shape. The stator core 110 is formed from a plurality of individual core segments 120. Each core segment 120 comprises a body 140, which defines a portion of the annular ring of the stator core 110, and a pole tooth 150 which projects radially inwardly from the annular ring defined by the bodies 140. The body 140 and tooth 150 of each segment form an L-shaped configuration. Adjacent core segments 120 are connected by a hinge connection 130 such that the array of segments can be stamped as a single open array (as shown in Figure 3) before being deformed into the closed annular shape shown in figure 2. The shape and features of the stator core will be described further below with reference to the detailed view of figure 3a, the detail of region X shown in figure 4 and the connector arrangement of area Y shown in figures.

As noted above, figure 3 shows the array of stator core segments 120 in an open configuration. Typically the open configuration may configure the segments 120 in a linear array (which can be advantageous in automated manufacture). The stator core 110 may be initially stamped in this open configuration. In the illustrated embodiment the stator core 110 comprises fifteen substantially identical segments 120 (but it will be appreciated that an appropriate number may be selected depending upon the design of the electric machine -for example based upon the number of poles and coils required). The segments 121 and 122 at the respective opposite ends of the array of segments are each connected to a single adjacent segment and have a free end face 191, 192 provided with respective complementary interconnecting features (explained further below with reference to figure 5). The intermediate segments 120 are each connected on both sides to an adjacent segment (having an identical profile) by hinge connectors 130.

The features of an individual segment 120 will now be described with reference to the enlarged detail shown in the lower portion of figure 3 and the enlarged detail of figure 4. As noted above, each segment 120 has a generally L-shaped configuration defined by the body portion 140 and a single pole tooth 150. The body 140 is a segment of an annular ring and having a radially outer circumferential surface 149 and a radially inner circumferential surface 148. To aid positioning of the coils 300 the inner surface 148 may be defined by tangential sections 148a and 148b (best seen in figure 3B) that generally approximate a continuous circular profile.

The pole tooth 150 extends radially away from the body 140 and has a transverse width defined by two circumferentially spaced apart sides 151 and 152. A footprint F of the pole tooth 150 may be defined in the body 140 as the region between the spaced apart side 151 and 152 of the pole tooth 150. In other words, the footprint F of the pole tooth 150 is the area of the body 140 which underlies the pole tooth. The distal end 159 includes a pair of tooth tips 160a, 16013 which have an initial, stamped, configuration (as shown in figure 3) in which they extend generally radially and a final assembled configuration (as shown in figure 2) in which they extend generally circumferentially (and therefore transversely relative to the pole tooth 150 to provide a flange at the pole tooth end 159).

The circumferentially spaced apart ends of the body 140 comprise first and second complementary interface surfaces 141 and 142. The first interface surface 141 is arranged at an oblique angle to the radial direction and tapers circumferentially away from the body portion 140 of the segment 120 as it extends from the inner surface 148 to the outer surface 149. The second interface surface 142 is arranged at a corresponding oblique angle to the radial direction and tapers circumferentially towards the body portion 140 of the segment 120 as it extends from the inner surface 148 to the outer surface 149. The second interface 142 commences at a small flange 146 which extends away from the foot of the side wall 152 and forms part of the inner face 148 of the body. The surface 142 then extends back through substantially the full width of the footprint F of the pole tooth 150.

In the open/linear configuration (as shown in figure 3) adjacent interface surfaces 141, 142b and 142, 141b of neighbouring segments 120 are in a spaced apart opposed arrangement. When the stator core 110 is in the closed configuration (as shown in figures 2 and 4) the complementary interface surfaces match and abut the other complementary surface 142b and 141b of the adjacent segment. Thus, it can be appreciated that embodiments ensure that the joining line between adjacent segments of the stator extends at an angle (oblique relative to both the radial and circumferential directions) through the footprint of each pole tooth 150. The applicant has found that positioning the joining line between segments in the footprint of the pole tooth provides both structural and magnetic field advantages in the final stator 110. Further, the resulting L-shape of the segments 120 (rather than a T-shape as in prior arrangements) may provide advantages in enabling clearer access to the pole tooth 150 to provide a coil 300 thereon when assembling or manufacturing the stator.

The interface surfaces 141, 142 have matching profiles and are also provided with inter-engagement features 143, 144. The inter-engagement features ensure that adjacent segments positively align into a pre-determined location when brought together. In the illustrated embodiments the inter-engagement features comprise a rib or protrusion 143 on the first surface 141 and a corresponding recess 144 on the second surface 142. It may be noted that the rib 143 is provided with a rounded nose (and recess 144 has a corresponding profile) which may help to cam the inter-engagement features into alignment during roll up of the stator 100.

At the outer surface 149 of the body 140 the interface surfaces end at a hinge 130 which adjoins the core segments 120. Each hinge 130 is arranged as a living hinge with a web 131 extending generally circumferentially along a section of the outer surface 149 of the body 140. The web 131 extends from a first end 132 which is integral with the first end 141 of a segment to a second end 133 which is integral with the second end 142 of the neighbouring segment 120. The web 131 is separated from the body 140 of the segment by a slot 135. The slot 135 and the web 131 both extend in longitudinally in a direction which is generally circumferentially aligned. When the stator core 110 is in the open configuration, one circumferential end of the slot 135 is closed (with a rounded curvature to allow bending without stress concentration) and the other end terminates in an open mouth which is contiguous with the spacing between the opposed adjacent sides 141 and 142 of adjacent segments.

The hinge 130 has a natural resilience as a result of its metal material and having been stamped in the open configuration. As seen in figure 4, when the stator body segments 120 are moved to the closed/annular configuration, with the interface surfaces 141, 142 abutting, the web 131 of the hinge 130 is elastically folded down against the body 140 of the stator core. In this configuration the web 131 may function as a leaf spring and provides a tension in the direction of arrow T. This tensile force acts to urge the engagement features 143 and 144 into position to firmly secure and align the segments 120.

As noted above, the end segments 121 and 122 of the stator 110 may be provided with end faces 191, 192 with inter-engagement features. This may provide a stator core 110 which can be resiliently engaged in its closed annular configuration (as shown in figure 2) without the need for additional processing steps such as applying a bead of solder or welding. This may provide significant manufacturing efficiency advantages. Additionally or alternatively, the inter-engagement features may provide a stator core 120 which accurately self-aligns in the closed configuration.

The engagement features of the illustrated embodiment are shown in isolation in figure 5. The end faces 191 and 192 of the end segments 121,122 have an interface which is generally similar to the interface 141, 142 between intermediate segments 120. In particular, the alignment and position of the interface is similar with the end face 192 extending at an oblique angle through the footprint of the pole tooth 150 of end segment 122. In place of the alignment feature 143, 144 and hinge 130 of the intermediate segments the end segments have complementary engagement features 196 and 197 formed on their respective end faces 191 and 192. A first one of the engagement features comprises an arm 195 which extends along the general direction of outer surface 149 (for example it may be circumferentially extending or tangential to approximate the circumferential direction) and carries a latch head 196. The latch head 196 projects inwardly from the arm 195 and has a barbed profile being angled back towards the end face 191. The corresponding feature of the other end 122 provides a recess 193 into which the latch head 196 is to be retained. The recess 193 extends radially inwardly away from the outer surface 149 and is angled to receive and retain the latch head 196. The recess 193 may be conveniently formed on a protruding arm 194 which extends outwardly from the surface 192 of end 122. The arm 194 may have a branched profile (with a Y-type shape) to provide features which the latch head 196 can pass over and engage. When the array is moved into its closed/annular configuration the surfaces 191 and 192 are brought into alignment and the latch head 196 will deflect, bending the arm 195 radially outwardly, to pass over the arm 194. Once the surfaces 192 and 194 come into full circumferential alignment the barb of the latch head 196 will be able to resiliently snap back (radially inwardly) from its deflected position into the recess 193 such that it is in the engaged position shown in figure 5. Once in this position the angle of the barbed latch head 196 and latch surface of the recess 193 ensure that the engagement features remain coupled.

The steps of assembling a stator in accordance with an embodiment is shown in figure 6. A stator core 110 in the form of an articulated array of segments 120 each having a pole teeth 150 is provided in an open linear configuration as shown in figure 6A. Coils 300 are provided on each pole tooth, for example by sliding pre-wound insulator bobbins over each tooth 150 in a linear manner. Advantageously in order to automate assembly the coils may for example be provided in a jig such that all the coils may be aligned and positioned on the pole teeth as a group. The coils are secured on the pole teeth by pressing the tooth tips 160 into their transverse position. The stator core is then rolled into the closed array as shown in figure 9C. In rolling the stator core, each adjacent core segment 120 rotates into position about its hinge 130 and brings the surfaces 141 and 142 into abutment. As the end sections 122 and 121 are brought into position the latch head 196 engaging the recess 193 to hold the stator core in its closed configuration without the need for an additional processing step. The stator assembly can then be completed by electrically connecting the coils via bus bars 101 to connectors 105.

Although the invention has been described above with reference to preferred embodiments, it will be appreciated that various changes or modification may be made without departing from the scope of the invention as defined in the appended claims. For example, whilst the illustrated embodiment described above comprises an internal rotor and external stator embodiments of the invention need not be limited to such an arrangement. In this regard the skilled person will appreciate that some motors use a stator having an internal annular stator core with outwardly projecting pole teeth. It will be appreciated that embodiments of the present disclosure can easily be adapted to such an arrangement without the departing from the scope of the invention.

Claims

Claims 1 A stator core comprising an articulated array of core segments each segment being hingedly connected to at least one adjacent core segment such that the core has a first configuration in which the core segments form an open array and a second configuration in which the core segments form a closed annular array, and each core segment has an L-shaped profile comprising: a body defining a segment of an annular ring; and a pole tooth projecting radially from the annular ring segment; and wherein the body comprises first and second complementary interface surfaces at respective circumferentially opposing sides of the body and one of the interface surfaces extends through a circumferential footprint of the pole tooth.
2. A stator core as claimed in claim 1, wherein first and second complementary interface surfaces of adjacent core segments abut when the stator core is in a closed configuration.
3. A stator core as claimed in claim 1 or 2 wherein the interface surface extends through substantially the entire circumferential extent of the footprint of the pole tooth.
4. A stator core as claimed in claim 1, 2 or 3, wherein the interface surface extends at an oblique angle through the body.
5. A stator core as claimed in any preceding claim, wherein the core segment comprise a flange at the foot of the pole tooth and interface surface extending through the footprint of the pole tooth extend from the flange through the footprint of the pole tooth.
6 A stator core as claimed in any preceding claim, further comprising a hinge connection between adjacent first and second complementary interface surfaces of adjoining core segments.
7. A stator core as claimed in claim 6, wherein the hinge connection comprises a web.
8. A stator core as claimed in claim 7, wherein the web is circumferentially elongate.
9 A stator core as claimed in claim 7 or 8, wherein the web provides a resilient connection between the adjoining core segments to bias the core segments towards the open position.
10. A stator core as claimed in any preceding claim, wherein the first and second complementary interface surfaces comprise at least one inter-engagement feature.
11. A stator core as claimed in claim 10, wherein the inter-engagement feature radially aligns adjacent segments in the closed position.
12. A stator core as claimed in claim 10 or 11 in combination with claim 9, wherein when the stator is in the closed configuration the web provides a tensile force which acts to hold the inter-engagement feature in alignment.
13 A stator core as claimed in any preceding claim, wherein the array of articulated core segments comprises first and second end segments which are hingedly connected to only one adjacent core segment and the core segments intermediate to the end segments are each hingedly connected to a pair of adjacent core segments.
14. A stator core as claimed in claim 13, wherein the first end segment comprises a first end face and the second end segment comprises a second end face and wherein the end faces are be provided with complementary engagement features.
15. A stator comprising a stator core as claimed in any preceding claim and a coils disposed on each pole tooth.
16. An electric machine comprising a stator as claimed in claim 15 and a rotor.
17 A method of assembling a stator, the method comprising the steps of: providing a stator core comprising an articulated array of pole teeth in an open linear configuration; providing a coil winding on each pole tooth; rolling the stator core into a closed annular array; wherein rolling the stator core into a closed array comprises hinging interface surfaces formed in the footprint of each pole tooth into engagement.
18 A method of assembling a stator, the method comprising the steps of: providing a stator core comprising an articulated array of pole teeth in an open linear configuration; providing a coil winding on each pole tooth; rolling the stator core into a closed annular array; wherein rolling the stator core into a closed array comprises bringing opposing free ends of the stator core into abutment and engaging complementary engagement features provided on the ends to latch the stator core in a closed annular configuration.