NZ523325A - Stator construction - Google Patents

Abstract

A method of assembling a toroidally wound electrodynamic machine wherein the electromagnetic core consists of at least one length of flexible magnetic material, and the magnetic material is positioned within a winding consisting of a plurality of separated wound coils by introducing one end of the magnetic material between two adjacent wound coils and pushing the magnetic material with sufficient force to slide through each of the wound coils and to form the magnetic material into a helical or spiral coil within the wound coils.

Description

Patents Form # 5 523325 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION AFTER PROVISIONAL # 523325 DATED : TITLE : December 2002 Stator Construction 12 DEC 2003 -ggc Eiypn We, Wellington Drive Technologies Limited Address: 13 William Pickering Drive, North Harbour, Auckland, New Zealand Nationality: A New Zealand citizen/company do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: 1 - PF05.JWP FEE CODE 1050 STATOR CONSTRUCTION FIELD OF THE INVENTION This invention relates to toroidally wound electrodynamic machines.

BACKGROUND OF THE INVENTION Toroidally wound electrodynamic machines consist of stator and rotor, the stator being formed from a toroidal electromagnetic core with a coil or coils wound upon that core, the coil axis being substantially tangential to the core. Such stators are by their very nature relatively difficult to construct, in that complex machinery is required to form the windings about the core. To overcome this difficulty some manufacturers have wound the coils onto 10 bobbins using simple winding equipment, and the wound bobbins are later introduced onto a split magnetic core. The discontinuity in the core introduces an airgap in the electromagnetic core, reducing flux density and potentially introducing saliency into the operation of the machine. Such a construction is shown in US patent specification 469 080.

Alternative constructions provide multiple stacked core sections, each with a split allowing a 15 bobbin to pass through, with the sections being initially aligned to allow this and later rotated to separate the splits as much as possible. This structure has both constructional problems, flux density problems, and saliency problems. Such a construction is shown in US patent 4 103 197.

DEFINITIONS Within this specification the following terms have the stated meanings when referring to electromagnetic cores. "helical" refers to a material arranged in a substantially constant pitch, substantially constant diameter helix of more than one turn. Typically the material of which the helix is made is wider radially than it is along the axis of the helix. "spiral" refers to a material arranged in an ever decreasing or increasing radius. The material is normally of constant cross-section and wider normal to the radius than it is thick along the radius. 130501 NZ_DPCS_101 .doc/PA "toroidal" refers to a material of substantially constantly repeating cross section arranged in a torus. Typically the cross section may be constant as a whole but it may also include radial inner or outer protrusions at regular intervals.

OBJECT OF THE INVENTION It is therefore an object of the present invention to provide a toroidally wound electrodynamic machine constructed using pre-formed windings about a magnetic core in which the core has no discontinuities in the tangential direction. Such a machine will provide improved efficiency or reduced saliency in operation, or will at least provide the public with a useful choice.

STATEMENT OF THE INVENTION Accordingly, the invention may broadly be said to consist in a toroidally wound electrodynamic machine wherein the electromagnetic core is made from at least one length of magnetic material, and the magnetic material is positioned within a winding consisting of 15 a plurality of separated wound coils, by introducing one end of the magnetic material between two adjacent wound coils and pushing the magnetic material with sufficient force to slide through each of the wound coils and to form the magnetic material into a helical or spiral coil within the wound coils.

Preferably the magnetic material that is positioned within the winding has sufficient length to 20 form at least one complete turn.

Preferably the magnetic material has sufficient length to form at least two complete turns.

Preferably the magnetic material is soft iron.

Preferably the magnetic material is in the form of a thin flat bar of constant cross-section. Preferably the bar is arranged in the form of a spiral.

Alternatively the bar is arranged in the form of a helix. 130501NZ DPCS 997.doc/PA Preferably at least one side of the magnetic material is etched or coated to reduce eddy currents.

Preferably at least one of the wound coils arranged in the circular pattern has a larger mouth leading to its internal diameter, than an adjacent wound coil in the pattern, so as to provide a 5 simpler path to insert the magnetic material.

Preferably where the magnetic material is a spiral, this larger mouth protrudes in the radial direction Alternatively where the magnetic material is a helix, this larger mouth protrudes in the axial direction Alternatively the gap between coils is sufficiently large to easily feed the magnetic material between coils when all coils have identical mouths Preferably the toroidally wound electrodynamic machine is an electric motor.

The invention may also broadly be said to consist in the parts, elements and features referred 15 to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of the parts, elements or features, and where specific integers are mentioned herein which have known equivalents, such equivalents are incorporated herein as if they were individually set forth.

One preferred form of the invention will now be described with reference to the 20 accompanying drawings in which, FIGURE 1 is a perspective view of a plurality of bobbins carrying wound coils and captured inside a frame allowing insertion of the core.

FIGURE 2 shows a side view of the frame FIGURE 3 is a cross-section along line A-A of the frame and bobbins 25 FIGURE 4 is a perspective view of a completed coil assembly still located in the frame 130501NZ DPCS 997.doc/PA FIGURE 5 is a side view of the completed coil assembly within the frame FIGURE 6 is a cross-section along line B-B of the frame and completed assembly FIGURE 7 is a side view of a bobbin assembly being fed with a helical core FIGURE 8 is a top view of a bobbin assembly with less bobbins fed with a spiral coil. 5 EXAMPLE 1 With reference to Figure 3, a frame 5 is loaded with bobbins 1 such that the bobbins have no appreciable gap between them. One of the bobbins, 4, has an enlarged mouth on one side and is tilted upwards to allow entry of one end of the core strip 3.

Core strip 3 is stiff enough in relation to the bobbin size and the frame curvature that it can 10 be fed into the central cavity of the bobbins sufficiently to complete at least two circuits. Preferably it is sufficiently stiff that it can complete sufficient circuits to substantially fill the bobbin cavity cross-section.

As best shown in Figure 6, once the core is packed the strip is severed at the feed bobbin, and the top of feed bobbin 4 is depressed into line with the rest of the bobbins, the lower 15 edge of the feed bobbin projecting below that of the other bobbins.

The core strip may be etched or coated to reduce the conductive contact between the layers of the inserted coil and so reduce eddy currents.

The core strip may consist of one or more layers of magnetic material at least temporarily adhered together to allow insertion.

Alternatively one or more core strips may be inserted independently, offset from each other in an axial direction.

EXAMPLE 2 Figure 7 shows a helical coil of constant pitch, diameter and cross-section at 701 which is fed into a circular assemblage of winding coils 702 by feeding an end of the helical coil into 25 the centre of the winding at 704. The bobbin 705 is longer than adjacent bobbins, providing 130501NZ DPCS_997.doc/PA an aperture into which the coil is fed. The helical coil is sufficiently stiff, and the inner surface of the winding coils sufficiently low in friction, that the helical coil may be fed until the winding space is as packed as possible by multiple turns of the helical coil. As shown the winding coils are on bobbins of low friction material, typically reinforced nylon.

EXAMPLE 3 Figure 8 shows a stator 801 as in Figure 1, but in which there are only eight winding coils 802. This provides a larger gap 803 between the pairs of coils and a spiral coil of magnetic material 804 may be introduced between two adjacent winding coils without offsetting them in any way, the flexibility of the stator core material being sufficient to allow what bending is required.

Thus it can be seen that at least the preferred form of the invention provides a toroidally wound electrodynamic apparatus having an electromagnetic core without joins. 130501NZ DPCS 997.doc/PA

Claims (16)

CLAIMS:

1. A method of assembling a toroidally wound electrodynamic machine wherein the electromagnetic core consists of at least one length of flexible magnetic material, and the magnetic material is positioned within a winding consisting of a plurality of separated 5 wound coils by introducing one end of the magnetic material between two adjacent wound coils and pushing the magnetic material with sufficient force to slide through each of the wound coils and to form the magnetic material into a helical or spiral coil within the wound coils.

2. A method as claimed in claim 1 wherein the or each length of magnetic material that is 10 positioned within the winding has sufficient length to form at least one complete turn.

3. A method as claimed in claim 2 wherein the or each length of magnetic material has sufficient length to form at least two complete turns.

4. A method as claimed in claim 1 wherein the magnetic material is soft iron.

5. A method as claimed in claim 4 wherein the soft iron is in the form of a thin flat bar of 15 constant cross-section.

6. A method as claimed in claim 3 wherein the magnetic material is arranged in the form of a spiral.

7. A method as claimed in claim 3 wherein the magnetic material is in the form of a helix

8. A method as claimed in claim 1 wherein at least one side of the magnetic material is 20 etched or coated to reduce eddy currents.

9. A method as claimed in claim 1 wherein at least one of the wound coils has a larger mouth leading to its internal space than an adjacent wound coil, to provide an entry path to insert the magnetic material.

10. A method as claimed in claim 9 wherein when the core is a spiral core the larger mouth is 25 larger radially. 130501 NZ_DPCS_997.doc/PA 8

11. A method as claimed in claim 9 wherein when the core is a helical core the larger mouth is larger axially.

12. A method as claimed in claim 9 wherein the electromagnetic material is in the form of a constant rectangular cross-section magnetic material.

13. A method as claimed in claim 1 wherein the toroidally wound electrodynamic machine is an electric motor.

14. A toroidally wound electrodynamic machine assembled by the method of claim 1 and having a stator core consisting of at least one length of flexible magnetic material forming at least one complete turn of a torus, spiral, or helix, such core being positioned within the centres of a plurality of separated wound coils arranged such that their axes are substantially tangential to the core.

15. A toroidally wound electrodynamic machine as claimed in claim 14 where in at least one length of the flexible magnetic material forms at least two complete turns of a spiral or helix.

16. An electric motor when assembled by the method of any of claims 1 to 12 PIPERS Attorneys for Wellington Drive Technologies Ltd INTELLECTUAL PROPER™ OFFICE 1 6 MAR 2005 RECEIVED 130501NZ_TIExamResponse_20050316_PC.doc