STATOR CORE

Abstract

A stator core for an electric machine includes a stator tooth for mounting an electromagnetic coil and a cooling structure associated with the stator tooth. The cooling structure has multiple sections adjacent each other along a direction parallel to the axis of the stator core. Each section includes multiple channels for the flow of a coolant. The plurality of channels are spaced azimuthally from each other and are arranged asymmetrically about the stator tooth. Adjacent sections of the cooling structure along the axis of the stator core are substantially identical to each other and are rotated 180 degrees about a radial direction relative to each other.

Claims

1. A stator core for an electric machine, wherein the stator core extends azimuthally around an axis, wherein the stator core comprises: a stator tooth for mounting an electromagnetic coil; and a cooling structure associated with the stator tooth; wherein the cooling structure comprises a plurality of sections adjacent each other along a direction parallel to the axis of the stator core; wherein each of the plurality of sections comprises a plurality of channels for the flow of a coolant; wherein the plurality of channels are spaced azimuthally from each other; wherein the plurality of channels are arranged asymmetrically about the stator tooth; and wherein adjacent sections of the cooling structure along the axis of the stator core are substantially identical to each other and are rotated 180 degrees about a radial direction relative to each other.

2. A stator core as claimed in claim 1, wherein the plurality of channels are symmetrical about a plane of symmetry in which lies the axis of the stator core and a radial direction, wherein the plane of symmetry is offset azimuthally from a plane in which lies the axis of the stator core and a radial direction passing through the centre of the stator tooth.

3. A stator core as claimed in claim 1, wherein the adjacent sections of the cooling structure are arranged relative to each other such that the plurality of channels in one cooling structure section are in fluid communication with the plurality of channels in the adjacent cooling structure section.

4. A stator core as claimed in claim 1, wherein each section of the cooling structure comprises a plurality of sheets laminated together.

5. A stator core as claimed in claim 4, wherein each sheet of the plurality of sheets forming each section of the cooling structure has substantially the same size and shape.

6. A stator core as claimed in claim 1, the plurality of channels extend in a substantially axial direction.

7. A stator core as claimed in claim 1, wherein the plurality of channels are enclosed.

8. A stator core as claimed in claim 1, wherein the plurality of channels are spaced from each other azimuthally.

9. A stator core as claimed in claim 1, wherein each section of the cooling structure is formed as a single piece that extends azimuthally around the axis of the stator core.

10. A stator core as claimed in claim 1, wherein the stator tooth has a substantially constant cross section.

11. A stator core as claimed in claim 1, wherein the stator tooth is symmetric about a plane in which lies the axis of the stator core and a radial direction passing through the centre of the stator tooth.

12. A stator core as claimed in claim 1, wherein the stator tooth comprises a plurality of sections adjacent each other along a direction parallel to the axis of the stator core, wherein each stator tooth section is integrally formed with a respective cooling structure section.

13. A stator core as claimed in claim 1, wherein the cooling structure comprises a slot or groove that receives an end of the stator tooth.

14. A stator core as claimed in claim 13, wherein the stator tooth is a single tooth that is received by a slot or groove that is formed together by or in the plurality of cooling structure sections.

15. A method of manufacturing a stator core for an electric machine, the method comprising: forming a stator tooth for mounting an electromagnetic coil and a plurality of sections of a cooling structure associated with the stator tooth; wherein each of the plurality of sections comprises a plurality of channels for the flow of a coolant; wherein the plurality of channels are spaced azimuthally from each other; and wherein the plurality of channels are arranged asymmetrically about the stator tooth; and wherein the method further comprises: arranging the plurality of sections of the cooling structure adjacent each other along a direction parallel to an axis of the stator core by rotating adjacent sections of the cooling structure through 180 degrees about a radial direction relative to each other; wherein adjacent sections of the cooling structure along the axis of the stator core are substantially identical to each other.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0068] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:

[0069] FIG. 1 shows a shows a perspective view of a core of a stator;

[0070] FIG. 2 shows a plan view of the stator core shown in FIG. 1;

[0071] FIG. 3 shows an exploded view of two sections of the stator core shown in FIGS. 1 and 2;

[0072] FIG. 4 shows a close up view of a cross-section of a section of the stator core shown in FIGS. 1 and 2;

[0073] FIG. 5 shows a close up view of a section of the stator core shown in FIGS. 1 and 2;

[0074] FIG. 6 shows a perspective view of part of a core of a stator;

[0075] FIG. 7 shows a close up view of the stator core shown in FIG. 6;

[0076] FIG. 8 shows a perspective view of a section of a core of a stator;

[0077] FIG. 9 shows a close up view of the section shown in FIG. 8;

[0078] FIG. 10 shows a perspective view of a section of a core of a stator;

[0079] FIG. 11 shows one segment of the section of the stator core shown in FIG. 10; and

[0080] FIG. 12 shows one segment of a section of a core of a stator.

DETAILED DESCRIPTION

[0081] FIG. 1 shows a perspective view of a core 1 of a stator. The core 1 has an overall cylindrical shape about a longitudinal axis. The core 1 includes multiple stator teeth 2 that extend axially with a constant cross-section. The stator teeth 2 are spaced azimuthally from each other and are shaped to receive windings of the stator.

[0082] The stator teeth 2 of the core 1 extend radially inwards from a continuous outer rim 4. Multiple heat conducting fins 6 are arranged on the outside of the outer rim 4 to form a cooling structure. The heat conducting fins 6 project radially from the outer rim 4 and extend axially along the outer surface of the outer rim 4.

[0083] As will be explained in more detail below, the core 1 is formed from multiple sections, which are then assembled together. The heat conducting fins 6 in each section are aligned axially and spaced azimuthally from each other, such that there is a channel therebetween. The heat conducting fins 6 in each section are offset azimuthally from the heat conducting fins 6 in each adjacent section, in an arrangement such that flow paths through the channels between the heat conducting fins 6 of adjacent sections of the stator core 1 are formed.

[0084] FIG. 2 shows a plan view of the stator core shown in FIG. 1. Also shown is the flow of coolant fluid through the channels formed by the heat conducting fins 6 (and, e.g., an outer sleeve (not shown)). The coolant fluid (at a cooler temperature) enters the channels of the stator core 1 at one end and flows in a substantially axial direction through the channels.

[0085] As the coolant fluid passes through the channels, it is heated by, inter alia, the heat conducting fins 6 of the stator core 1, such that the coolant fluid (at a higher temperature) exits the channels of the stator core 1 at the other end of the stator core 1. The heating of the coolant fluid thus acts to cool the stator core 1.

[0086] FIG. 3 shows an exploded view of two sections 8 of the stator core 1 shown in FIGS. 1 and 2. The sections 8 are formed by stamping out the cross-sectional shape of the section from a sheet of electrical grade steel and laminating multiple such stamped shapes together, in an aligned manner, using a dielectric bonding agent, to form the laminated sections 8.

[0087] Each of the sections 8 is substantially identical and the stator core 1 is formed by assembling adjacent sections, which are rotated through 180 degrees relative to each other (about a direction perpendicular to the longitudinal cylindrical axis), such that the stator teeth 2 align with each other, as shown in FIG. 1.

[0088] FIG. 4 shows a close up view of a cross-section of a section 8 of the stator core 1 shown in FIGS. 1 and 2. From this, it can be seen that the heat conducting fins 6 are not symmetrically arranged about the centre of the stator tooth 2. Instead, they are offset from the centre of the stator tooth 2. This pattern applies for each stator tooth 2 of the section 8 of the stator core 1.

[0089] FIG. 5 shows a close up view of a section 8 of the stator core 1 shown in FIGS. 1 and 2. The offset arrangement of the heat conducting fins 6 has the effect, as shown in FIG. 5, that when two sections 8 of the stator core 1 are assembled adjacent each other, with one being rotated through 180 degrees relative to the other, the heat conducting fins 6 (and thus also the channels defined therebetween) do not align but are instead offset from each other between the adjacent sections 8.

[0090] The offset in the channels between the heat conducting fins 6 causes a non-linear, disrupted flow path for the coolant fluid. This causes turbulence in the coolant fluid that is used to cool the stator, which improves the rate of cooling.

[0091] FIG. 6 shows a perspective view of part of a core 101 of a stator. FIG. 7 shows a close up view of the stator core 101 shown in FIG. 6. The stator core 101 shown in FIGS. 6 and 7 is similar to that shown in FIGS. 1 to 5, except that it is shown with an outer sleeve 110 that encloses the heat conducting fins 106, thus forming enclosed channels. In FIG. 7, only part of the outer sleeve 110 is shown, with the heat conducting fins 106 being shown exposed, for illustration.

[0092] The sleeve 110 may be fitted after the stator core 101 has been formed. Alternatively, the sleeve 110 may be formed integrally with the stator teeth 102, the outer rim 104 and the heat conducting fins 106. In this arrangement, the sleeve 110 is stamped out with the rest of the shape (i.e. the stator teeth 102, the outer rim 104 and the heat conducting fins 106) of the stator core 101.

[0093] FIG. 8 shows a perspective view of a section 208 of a core of a stator. FIG. 9 shows a close up view of the section 208 shown in FIG. 8. The section 208 of the stator core is similar to that shown in FIGS. 1 to 5. However, in the section 208 shown in FIGS. 8 and 9, the outer rim 204 and the heat conducting fins 206 are formed separately from the stator teeth 202. In this section 208, each stator tooth 202 is formed with a dovetail projection 212 that fits into a corresponding dovetail keyway 214 formed in the outer rim 204.

[0094] The outer rim 204 and the heat conducting fins 206 may be formed with the keyway present, e.g. when stamping out the outer rim 204 and the heat conducting fins 206. Alternatively, the keyway may be formed after the sheets of the outer rim 204 and the heat conducting fins 206 have been laminated together, with the keyway being machined through the section (or indeed multiple sections that have been connected together).

[0095] FIG. 10 shows a perspective view of a section 308 of a core of a stator. The section 308 is similar to that shown in FIGS. 8 and 9, except that it is formed in segments 316, each segment 316 including a single stator tooth 302.

[0096] FIG. 11 shows one segment 316 of the section 308 of the stator 301 shown in FIG. 10. As can be seen, the outer rim 304 of the segment 316 has a dovetail projection 318 and a dovetail keyway 320 on opposite sides that allow the segments 316 to be connected together to form the whole section 308. This allows the segments 316 to be formed as smaller pieces initially and thus creates less material waste.

[0097] FIG. 12 shows a similar segment 416, except in this design the stator tooth 402 is formed integrally with the outer rim 404 and heat conducting fins 406.

[0098] For the stator cores shown, the fully assembled core is to be fitted into a cylindrical housing of an electric motor. Stator windings are fitted to the teeth of the stator core and a rotor is inserted into the void within the stator core to form the electric motor.

[0099] Thus, in at least some embodiments, by arranging substantially identical sections of cooling structure relative to each other along the length of the stator core, with adjacent sections rotated through 180 degrees relative to each other, the channels in adjacent sections are offset from each other, owing to the asymmetry in the channels relative to the stator tooth (which has a defined position, azimuthally, along the axis of the stator core). Offsetting the channels from each other causes deviations in the flow path through the cooling structure. This causes turbulence in the fluid coolant that is used to cool the stator core, which improves the rate of cooling. Forming the cooling structure in this arrangement, from substantially identical sections, allows the stator core to be manufactured simpler and cheaper.