GB2485185A - Axial gap electrical machine having integrated stator - Google Patents

Abstract

An axial-gap electric machine has a stator 1110 comprising a planar insulation structure integrated with plural planar conducting layers containing winding and electric circuitry conductors for electronic components 300 of a matching circuit (e.g. a driver or converter). The stator has plural parallel conducting layers each comprising planar coils distributed about and perpendicular to the rotation axis (fig 3a). The stator coils can be arranged as single, two or three phase and realized as a multilayer printed circuit board (PCB). The coils can comprise double, oppositely wound spirals, (fig 2a, 910) connected by internal vias (fig 2a, 1112). The stator may further comprise magnetic cores (fig 8b, 1200) inserted into openings (fig 8b, 1116) in the stator; heat sinks (fig 6b, 400) which can have radial slots to allow a radial flow of cooling air; radial cooling liquid ducts; and radial cuts to prevent eddy-currents. The stator may be enclosed in a case (fig 9d, 1400), or have cooling channels (fig 10a, 455) attached to the heatsink, through which liquid circulates. The stator can be used in a brushless DC machine, such as a generator.

Description

INTEGRATED STATOR BRUSHLESS AXIAL AIR-GAP ELECTRIC MACHINE

BACKGROUND

1. TECHNICAL FIELD

[0001] The present invention relates to axial air-gap electric machines, such as electric machines and generators, and, more particularly, to an electric machine or generator whose stator is an integrated part based on a multilayer conductors board (e.g. Printed Circuit Board -PCB) incorporating winding conductors and other conductors for interconnecting electronic components of the attached electronic circuit mounted on this board.

2. DISCUSSION OF RELATED ART [0002] There are prior art brushless axial gap electric machines incorporating at least one disk type stator made as assembly of separated essentially stand-alone components. The stators may be either of core type which comprises wound coils, magnetic circuit member (core), insulation members, e.g. slot insulation paper; or of coreless type which lacks a core and comprises only winding coils and optionally a support member.

[0003] All these structures incorporate coils to be wound from magnet wire and after it inserted into core or secured on a support member -all this requires a rather much of labor consumption and applying a number of different technological processes (coil reeling; coil insertion / placement; inter-coil electric connection; e.g. by soldering; insulating impregnation etc.).

[0004] Korean Patent Document No. 20010094208 discloses an axial gap brushless DC motor with a PCB pattern used to eliminate cogging torque and achieve a compact size. Canadian Patent No. 2646031 discloses an ultra slim hybrid rechargeable electric energy source having a central stator plate with planar coils embedded in the plate and circularly distributed around a central axis. Both documents disclose a separate stator with a cumbersome configuration of connections.

BRIEF SUMMARY

[0005] Embodiments of the present invention provide a stator system comprising at least one n-phase stator, the n-phase stator comprising: a plurality of parallel conducting layers perpendicular to a rotation axis and embedded in an insulating structure, each layer comprising a specified number of planar conductive coils distributed circularly around the rotation axis, wherein: the coils are interconnected such as to form n groups of coils that are insulated from each other, in each group the coils are interconnected in a specified configuration, and the n groups are substantially congruent in configuration and are shifted by a definite angle in respect to each other; and conductors forming an electric circuitry connected to the coils in specified points, the conductors being useable for connecting electronic components thereto, wherein the stator system is useable in an axial flux (axial air-gap) brushless electric machine, such that each stator is producible by integrated technology.

[0006] These and/or other aspects and/or advantages of the present invention are set forth in the detailed description which follows; possibly inferable from the detailed description; and/or learnable by practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention will be more readily understood from the detailed description of embodiments thereof made in conjunction with the accompanying drawings of which: Figure la is external view of a permanent magnet electric machine with one coreless single-PCB stator according to the present invention Figure lb is an exploded view of a permanent magnet electric machine with one coreless single-PCB stator, according to some embodiments of the invention; Figure 2a is an external view of a single coreless PCB stator, according to some embodiments of the invention; Figure 2b is a cross-sectional view of a single coreless PCB stator, according to some embodiments of the invention; Figure 3a is an exploded view description of the multi-layer winding topology, according to some embodiments of the invention; Figure 3b is description of the multi-layer winding topology, according to some embodiments of the invention; Figure 4a is an external view of a permanent magnet electric machine with two tooth-core double-PCB stators, according to some embodiments of the invention; Figure 4b is an exploded view of a permanent magnet electric machine with two tooth-core double-PCB stators, according to some embodiments of the invention; Figure 5a is an external view of a double-PCB coreless stator adapted for conducting heat evacuation from the stator, according to some embodiments of the invention; Figure 5b is an exploded view of a double-PCB coreless stator adapted for conducting heat evacuation from the stator, according to some embodiments of the invention; Figure 6a is an external view of a double-PCB coreless stator adapted for self-ventilation, according to some embodiments of the invention; Figure 6b is an exploded view of a double-PCB coreless stator adapted for self-ventilation, according to some embodiments of the invention; Figure 7a is an external view of a double-PCB toothless core stator, according to some embodiments of the invention; Figure 7b is an exploded view of a double-PCB toothless core stator, according to some embodiments of the invention; Figure 8a is an external view of a double-PCB tooth core stator, according to some embodiments of the invention; Figure 8b is an exploded view of a double-PCB tooth core stator associated with two or more stator parts, according to some embodiments of the invention; Figure 9a is an external view of a multiple-PCI3 coreless stator adapted for direct liquid cooling, according to some embodiments of the invention; Figure 9b is a cross-sectional view of a multiple-PCB coreless stator adapted for direct liquid cooling, according to some embodiments of the invention; Figure 9c is a fragmental cross-sectional view of a multiple-PCB coreless stator adapted for direct liquid cooling, according to some embodiments of the invention; Figure 9d is a partly disassembled view of a multiple-PCB coreless stator adapted for direct liquid cooling, according to some embodiments of the invention; Figure Wa is an external view of a double-PCB core stator adapted for indirect liquid cooling, according to some embodiments of the invention; and Figure lOb is an exploded view of a double-PCB core stator adapted for indirect liquid cooling, according to some embodiments of the invention.

DETAILED DESCRIPTION

[0008] In contradiction to thc prior arts designs, the stator (which is the heart of the present invention) in the preferable embodiment of the electric machine per the present invention, is an integrated construction made e.g. as multilayer PCB (Printed Circuit Board) comprising conductors in its conducting layers building both coils of the electric machine winding and conductors for electric interconnection of electronic components of the matched electronic circuit mounted on this board.

[0009] According to the present invention it is provided an axial air-gap electric machine with rotational axis comprising: (a) at least one essentially planar stator made per integrated technology, e.g. as a single or multiple printed-circuit board (PCB), concentric with the rotational axis, including: (i) essentially planar insulation structure, (ii) a plurality of essentially planar conductive layers distanced each other in axial direction and integrated into above insulation structure, each comprising a plurality of conductors; (iii) electronic and other components mounted on surface or imbedded-into the insulation structure and electrically connected each other per a definite typology using a portion of the conductors comprised into the conducting layers, (iv) optionally -essentially planar heat sink member made from a heat-conducting material, e.g. aluminum, (v) optionally -magnetic circuit member made from a soft magnetic material, e.g. electric steel or soft ferrite; (b) at least one essentially planar rotating disk (rotor) facing to the stator through an axial air-gap and adapted to rotate around the rotational axis, including: (i) a periodical heteropolar axially magnetized magnetic system made either as a plurality of thin trapeze-like prismatic permanent magnet pieces or as a single-piece permanent magnet disk, (ii) optionally -essentially planar soft magnetic disk (back yoke) concentric to the magnetic system attached to it from a side opposing to the stator, (iii) optionally -constructive elements to provide the rotor rotation and increase its inertia if needed.

[0010] In an embodiment the stator is built by multilayer PCB technology and consists at least two portions: a portion of winding and a portion of circuitry. Conductors in the winding portion, are shaped like coils connected each other to form n (usually n=l, 2, 3) essentially identical angularly shifted phase group(s). Conductors in the circuitry portion are used for electric inter-connections between electronic components of a matched circuit (e.g. convertor of outputted voltage or transistor driver). The insulation structure in the circuitry portion is used for mechanical mounting these electronic components (e.g. by SMT).

[0011] In an embodiment the coils are made like multilayer sectorial spirals. In another embodiment the coils are traced along concentric or shifted wave-like lines. Required electrical connection between the coil conductors relating to different conducting layers are preferably made through VIAs (Vertical Interconnect Access).

[0012] In an embodiment in order to use efficiently the stator active area by decreasing in about two times the radial dimension of passive coil sections, each coil is made as 2 essentially equal stacked spirals wound in opposite directions. The spirals start from inside area and thus the coils do not have terminations outside that allows for the best using the stator peripheries. Furthermore each spiral is twice as narrow in its arc sections in respect to coils the size of the double spirals.

[0013] To increase the power ability, the stator comprises not one, but a plurality of identical PCBs to be allocated in parallel and concentrically and attached each other mechanically. They may be electrically connected each other or be electrically independent.

[0014] To keep the magnetic flux higher, the P03s in above embodiment, are stacked directly without any gaps in order to provide a minimal overall thickness. On another hand, to provide a better self-cooling capability, the PCBs in above embodiment, are distanced from each other by short air-gaps, e.g. 0.5-2 mm to form ducts for radial air-ventilation.

[0015] To provide a heat evacuation from the coils by heat conduction, the PCBs in above embodiment are distanced by planar heat conducting layers (heat sinks) e.g. from aluminum with numerous radial cuts to prevent eddy current in them. This heat sink layers in turn are attached to the housing construction to further conduct out the heat. On another hand, to combine the heat conduction with the self ventilation, the heat sink layers are implemented as separated sector elements to form radial ducts for air-ventilation.

[0016] To provide an enforced heat evacuation from the coils by direct liquid cooling, stator further contains construction means providing inlet and outlet of the cooling liquid. It flows either along outer PCB faces or in the gaps between the PCBs (in multi-PCB embodiment).

[0017] To provide an enforced heat evacuation from the coils by indirect liquid cooling in the embodiment with heat sink layers, they in turn comprise ducts for flowing the cooling liquid.

[0018] To provide a heat evacuation from the coils by heat conduction without decreasing the magnetic flux, the heat conducting member from the correspondent embodiment is done from soft magnetic material e.g. electric steel and thus performs a toothless core, [0019] To increase the magnetic flux keeping good heat conduction, the core in previous embodiment furthermore comprises annually distributed trapeze-like teeth on its face(s) while stator PCB(s) have the proper windows in which these core teeth are introduced by such a way that core and PCB(s) together form an integrated stator construction. The PCBs may be electrically connected each other or be electrically independent.

[0020] Figures la and lb describe an example of permanent magnet axial flux coreless double-rotor single-stator electric machine with the stator made per one of embodiments of the invention. It comprises 2 mechanically connected concentric disk rotors 200 and interposed stator 1000 which is actually a PCB 1100 carrying on electronic elements 300 serving for the electric machine (e.g. driver and servo-amplifier). The stator PCB 1100 incorporates the winding 1110 secured in the insulation structure 1115. The rotors 200 include permanent magnet(s) 220 and back yokes 210.

[0021] Figures 2a-2b elaborate above stator 1000 which is actually PCB 1100 carrying on electronic elements 300 electrically connected to the multi-layer winding 1110 secured in the insulation structure 1115. The winding consists of coils 1111 allocated on essentially all layers.

Coils 1111.1 ± 1111.12 are connected each other through vias 1112. To be adapted to the electric machine operation, the PCB may include holes 1113.

[00221 Figures 3a and 3b elaborate one of invented topology of the winding 1110 on an example of a single-phase winding allowing for allocating vias 1112 only inside the coils 1111 Furthermore all double-spiral coils 1111.1 ÷ 1111.12 (divided into 4 couples per layer) have arc width which twice narrower that radial width. Together it yields significantly more effective using the active stator area [0023] In this example the upper layer coils comprise 3 double-spiral coils 1111.1-1 with electrically connected spirals 1111.1-1-1 and 1111.1-1-2; and one double-spiral coil 1111.1-4 with electrically disconnected spirals 1111.1-4-1 and 1111.1-4-2 to form input terminal 111l.lin and output terminal 1111.lout. The rest layers include only double-spiral coils with electrically connected spirals.

[0024] The double-spiral coils of adjacent layers are serially connected through vias depicted by dashed lines 1119 (1119.1/2, 1119.2/3, ... 1119.11/12). The double-spiral coil of last layer 1111.12-1 is connected to the double-spiral coils of Pt layer 1111.1 per line 1119.12/1 and by such a way starts the new series of the serially connected double-spiral coils relating to all layers.

[0025] Figures 4a and 4b describe an example of permanent magnet axial flux core double-stator single-rotor electric machine. It comprises one disk rotor 200 interposed between 2 stators 1000A and 1000B made per one of embodiments of the present invention. Each stator incorporates a number (here two) of PCBs 1100.1A and 1101.2A (1100.1A and 1101.2A) secured on tooth core 1200A (1200B). Above PCBs including footprint for the electric machine electronics 300 (not shown) may be electrically connected and relate to different phases. Rotor rotating around shaft 210 further comprises permanent magnets 220 and retainer 230.

[0026] Figures Sa and Sb describe a stator 1000 per one of embodiments of the present invention adapted for enforced heat evacuation by heat conducting from the winding. The stator incorporates two identical PCBs 1100A, 1100B and interposed heat-sink 400 mechanically connected each other. Above PCBs include footprint for the electric machine electronics 300 (not shown). To prevent developing eddy-currents in the heat-sink 400 if it made from a metal (e.g. aluminum), it has many thin cuts 420 in the active area. To enhance a heat convection from the heat-sink 400 into ambient it consists of peripheral members 410.

[0027] Figures 6a and 6b describe a stator 1000 per one of embodiments of the present invention adapted for enforced heat evacuation from the winding by self-ventilation and partially by heat conduction. The stator incorporates two identical PCI3s 1100A, 110013 and interposed heat-sink 400 mechanically connected each other. Above PCBs include footprint for the electric machine electronics 300 (not shown). To allow for radial air flow, the heat-sink 400 made as an array of sectors 430 forming sufficient gaps 440. To prevent developing eddy-currents in the heat-sink 400 if it made from a metal (e.g. aluminum) it has many thin cuts 420 in the active area.

[0028] Figures 7a and 7b describe a core toothless stator 1000 per one of embodiments of the present invention The stator incorporates two identical PCBs 1100A, 1100B and interposed soft magnetic toothless core 1300 mechanically connected each other. Above PCBs include footprint for the electric machine electronics 300 (not shown).

[0029] Figures 8a and 8b elaborate core tooth stators incorporated to the electric machine described in Figures 4a and 4b. The stator 1000 comprises a number (here two, possibly any number) of PCBs 1100.1 and 1101.2 secured on tooth core 1200. Above PCBs comprise windings 1111.1 (1111.2) and insulating structure 1115.1 (1115.2) with holes 1116.1 (1116.2) and footprint for the electric machine electronics 300.1 (300.2) (not shown). The core 1200 consists of a yoke portion 1230 and teeth 1210 involved into the PCB holes 1116 by such a way that windings 1111 are allocated in the core slots 1220.

[0030] Figures 9a-9d describe a stator 1000 per one of embodiments of the present invention adapted for heat evacuation from the winding by direct liquid cooling. The stator incorporates a hermetic case 1400 with inlets I outlets 1410 and a hole 1420 for shaft. The case 1400 adapted to secure a number (here 3) of PCBs 1100.1, 1100.2, 1100.3 forming gaps 1120.1, 1120.2, 1120.3, 1120.4 playing a role of ducts for cooling liquid flowing along the PCBs sides. These PCBs comprise windings, insulating structure and footprint for the electric machine electronics (not shown).

110031] Figures lOa and lOb describe a stator 1000 per one of embodiments of the present invention adapted for heat evacuation from the winding by indirect liquid cooling. The stator incorporates two identical PCBs 1100A, 1100B and interposed heat-sink 400 mechanically connected each other. Above PCBs include footprint for the electric machine electronics 300 (not shown). To prevent developing eddy-currents in the heat-sink 400 if it made from a metal (e.g. aluminum), it has many thin cuts 420 in the active area. The heat-sink 400 incorporates on its external periphery, preferably on both sides, pipes 450 with inlets / outlets 455A (455B) and a hole 425 for a shaft. Through above pipes 450 the cooling liquid flows.

[0032] Embodiments of the present invention incorporate a n-phase stator (usually, n=1 or 2 or 3) comprising: an essentially planar insulation structure integrated inside with plurality of essentially planar conducting layers, each comprising a specified number of coiled conductors (coils) distributed circularly around a rotation axis, and a plurality of conductors forming an electric circuitry connected to the coils in definite points. This electric circuitry is adapted for electric connections to electronic components of a matching circuit (e.g. driver or converter) and their mechanical mounting. Within each group the coils comprised into different conducting layers are connected to each other by internal vias (Vertical Interconnect Access, positioned within the coils).

[0033] In some embodiments, the stator further comprises at least one of functional members: conducting heat-sink, air-cooled heat-sink, liquid cooled heat-sink, soft magnetic core, etc. [0034] In some embodiments, the coils in order to much effectively use the stator active area are made like double spirals starting and ending inside of coils.

[0035] In some embodiments, to increase the torque and power, the stator comprises a number of described above stator structures attached mechanically each other.

[0036] In embodiment, a stator system 900 (e.g. Figure 4A) comprises at least one n-phase stator 1000 that comprises: a plurality of parallel conducting layers perpendicular to a rotation axis 930 (e.g. Figure 1B) and embedded in insulating structure 1115, each layer comprising a specified number of planar conductive coils 1111 distributed circularly around rotation axis 930, wherein: coils 1111 are interconnected such as to form n groups of coils that are insulated from each other, in each group coils 1111 are interconnected in a specified configuration, and the n groups are substantially congruent in configuration and are shifted by a definite angle in respect to each other; and conductors forming electric circuitry 300 connected to the coils in specified points, the conductors being useable for connecting electronic components thereto, wherein stator system 900 is useable in an axial flux (axial air-gap) brushless electric machine, such that each stator 1000 is producible by integrated technology.

[0037] In embodiments, in at least one stator 1000 the specified configuration is characterized in that each planar coil 1111 comprises two planar spiral windings 915 (Figure 2A), wound in opposite directions, each spiral 915 having an external end 920 and an internal end 910 wherein spirals 915 are connected at their external ends 920 and have free internal ends 910 located within spirals 915. Each coil 1111 in each group is electrically connected with at least one coil 1111 of the same group that is positioned in an adjacent conductive layer, wherein coils 1111 are connected by their internal ends 910.

[0038] Advantageously in respect to Korean Patent Document No. 20010094208, embodiments of the current invention employ a multilayer integrated technology to generate the stator.

Furthermore, embodiments of the current invention include additional electric circuitry on the same PCB as the stator, thereby allowing a further compactization and increasing the simplicity of using the stator, integrating the stator in systems, cooling the stator etc. The interconnection of coils in emhodimcnts of thc currcnt invcntion is distinctly diffcrcnt from Korcan Patcnt Document No. 2001009420R, in which each coil has external contacts.

110039] Advantageously in respect to Canadian Patent No. 2646031, embodiments of the current invention present a much more effective interconnection of the coils, which improves the functioning and the performance of the stator, as well as simplifies the interface with the stator.

Moreover, embodiments of the current invention integrate additional electronic circuitry on the same board of the stator, further simplifying the usage of the stator, allowing miniaturization and effective cooling.

[0040] In the above description, an embodiment is an example or implementation of the invention. The various appearances of "one embodiment", "an embodiment" or "some embodiments" do not necessarily all refer to the same embodiments.

[0041] Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination.

Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

[00421 Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can he implemented in embodiments other than the ones

outlined in the description above.

[0043] The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described.

[0044] Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined.

OO45] While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.

Claims (14)

1. CLAIMSWhat is claimed is: 1. A stator system comprising at least one n-phase stator, the n-phase stator comprising: a plurality of parallel conducting layers perpendicular to a rotation axis and embedded in an insulating structure, each layer comprising a specified number of planar conductive coils distributed circularly around the rotation axis, wherein: the coils are interconnected such as to form n groups of coils that are insulated from each other, in each group the coils are interconnected in a specified configuration, and the n groups are substantially congruent in configuration and are shifted by a definite angle in respect to each other; and conductors forming an electric circuitry connected to the coils in specified points, the conductors being useable for connecting electronic components thereto, wherein the stator system is useable in an axial flux (axial air-gap) brushless electric machine, such that each stator is producible by integrated technology.
2. 2. The stator system of claim 1, wherein in at least one stator the specified configuration is characterized in that: each planar coil comprises two planar spiral windings wound in opposite directions, each spiral having an external end and an internal end, wherein the spirals are connected at their external ends and have free internal ends within the spirals; each coil in each group is electrically connected with at least one coil of the same group that is positioned in an adjacent conductive layer, wherein the coils are connected by their internal ends.
3. 3. The stator system of claim 1, wherein n is selected from 1, 2 and 3.
4. 4. The stator system of claim 1, comprising a plurality of n-phase stators positioned concentrically with a common rotation axis.
5. 5. The stator system of claim 1, wherein the insulating structures of the stators comprise openings within the coils, and the stator system further comprises a tooth soft magnetic core inserted into the openings, useable to increase magnetic flux through the at least one stator.
6. 6. The stator system of claim 1, further comprising at least one essentially planar toothless soft magnetic core positioned in parallel to the stators, useable to increase magnetic flux through the stators.
7. 7. The stator system of claim 1, further comprising at least one essentially planar heat sink contacting at least one of the stators and arranged to evacuate heat therefrom.
8. 8. The stator system of claim 7, wherein the heat sink comprises essentially radial slots arranged to allow an essentially radial airflow through them.
9. 9. The stator system of claim 7, wherein the heat sink is made of an electrically conducting material and comprises a plurality of circularly distributed radial rays having radial cuts, arranged to prevent eddy currents in the heat sink.
10. 10. The stator system of claim 7, wherein the planar heat sink further comprises fluid ducts arranged to allow circulating a cooling liquid therethrough.
11. 11. The stator system of claim 1, wherein each of the stators is realized as a printed circuit board (PCB), and wherein connecting coils of different layers is carried out by VIAs (Vertical Interconnect Access).
12. 12. The stator system of claim 1, wherein each stator is electrically insulated from its environment.
13. 13. The stator system of claim 1, further comprising a case enclosing the at least one stator and arranged to allow cooling liquid circulation therethrough to cool the at least one stator.
14. 14. An axial air-gap electric machine comprising the stator system of any of claims 1 to 13 and at least one coaxially rotating rotor.