The invention relates to an axial flux permanent magnet synchronous motor suitable for use in a laundry machine such as a washer, dryer or combination washer-dryer.
Direct-drive electric motors are commonly used in laundry machines. The motor directly drives a shaft without a belt or other form of motion transmission device between the rotor and shaft in order to rotate a tub inside of the machine where laundry is held. Requirements for a direct drive electric motor in a laundry machine include that the motor produce enough torque for reliable starting, minimise motor temperature rise while performing a desired cycle of motion to treat the laundry, minimise noise during operation, and be of a minimum thickness so the motor does not take space from the laundry machine tub (therefore the laundry machine can accommodate a larger amount of clothes for a given footprint-laundry machine capacity).
Electric motors used in direct-drive laundry machines are commonly of the radial flux—permanent magnet synchronous motor type (RF-PMSM), with an external rotor. The magnetic flux path is oriented radially.
An axial flux permanent magnet synchronous motor (AF-PMSM) is one in which the magnetic flux is oriented axially. AF-PMSM motors have previously been proposed for use in laundry washing machines (see US patent specification 20100275660 and PCT international patent specification WO2018155843) yet are not commonly in use and have proven difficult to implement in practice. In particular, optimal performance of the AF-PMSM motor depends on maintaining a constant air gap between the stator and rotor in the axial direction. This can be difficult to maintain in laundry machine applications where the motor is subject to internal forces and external forces/vibrations from revolving laundry loads.
It is an object of the invention to provide an improved or at least alternative form of AF-PMSM motor suitable for use to drive the load-containing drum in a laundry machine (such as a washer, dryer or combination washer-dryer) and an improved or at least alternative laundry machine driven by such a motor.
In broad terms the invention comprises an axial flux permanent magnet synchronous motor for use in a laundry machine, comprising:
In one embodiment the motor comprises a single rotor and a single stator.
In some embodiments said annular core of the stator has an inner diameter of between about 160 mm and about 250 mm.
In some embodiments said annular core of the stator has an outer diameter:
In some embodiments the torque constant is between 7-12 Nm/A.
In some embodiments the height of the stator core in the axial direction is about 30 mm or less.
In some embodiments the overall height in the axial direction is about 45 mm or less.
In some embodiments the rotor magnets and stator coils are spaced in the axial direction to define between them an air gap of between about 0.2 and 1.8 mm.
In some embodiments the air gap is between 0.4 and 1.5 mm.
In some embodiments the air gap is between 0.9 and 1.1 mm.
In some embodiments the air gap is approximately 1.2 mm.
In some embodiments the ratio of magnetic poles carried by the stator to magnetic poles carried by the rotor is 3:4.
In some embodiments the number of stator coils carried by the stator is 27.
In some embodiments the number of electromagnetic symmetries of the core is between 5 and 12, or optionally, is 9.
In some embodiments the stator coils are electrically connected to one another in a 3 phase configuration.
In some embodiments the stator core is spiral wound from electrical steel strips.
In some embodiments the stator core comprises a plurality of teeth extending in the axial direction, and wherein each one of said stator coils is carried by a corresponding one of said plurality of teeth.
In some embodiments the plurality of teeth have a height in the axial direction of about 26 mm or less.
In some embodiments adjacent ones of the plurality of teeth define between them a slot of about 10-20 mm in width.
In some embodiments the width of the slot at the outer perimeter of the annular core of the stator is greater than the width of the slot at an inner perimeter of the annular core of the stator.
In some embodiments the teeth have a tipless shape.
In some embodiments the teeth have chamfered edges.
In some embodiments the stator core comprises a yoke portion, with the plurality of teeth extending axially from one side of the yoke portion.
In some embodiments that yoke portion and teeth of the stator core are integrally formed.
In some embodiments the insulating structure comprises a plurality of bobbins, each mounted upon a one of said plurality of teeth and carrying a one of said plurality of stator coils.
In some embodiments the plurality of bobbins are made of a polymeric material.
In some embodiments one or more of the plurality of bobbins comprise a guide structure configured to maintain a physical separation between the electrical connections of adjacent stator coils.
In some embodiments the guide structure comprises a plurality of stepped guide surfaces and optionally one or more guide teeth dividing each stepped guide surface.
In some embodiments the magnets are made of sintered ferrite.
In some embodiments the plurality of permanent magnets are each a discrete piece of magnetic material formed in a rectangular shape, or alternatively, are each a discrete piece of magnetic material formed in a tapered shape.
In some embodiments each magnetic pole of the rotor is represented by a single discrete piece of magnetic material.
In some embodiments said plurality of permanent magnets are arranged about an annular region of the rotor concentric with the annular core of the stator.
In some embodiments said plurality of permanent magnets are arranged about an annular region of the rotor, and wherein the annular width of the stator core is between about 0 and about 10 mm less than the annular width of the annular region of the rotor.
In some embodiments the permanent magnets are between about 5 mm and 6.5 mm thick.
In some embodiments the permanent magnets are each a discrete piece of magnetic material having a constant thickness, or alternatively having a bread loaf shape.
In some embodiments the radially aligned edges of the permanent magnets are chamfered.
In some embodiments the permanent magnets comprise a rectangular portion wherein the radially aligned edges are parallel and a tapered portion wherein the radially aligned edges taper towards each other.
In some embodiments the tapered portion is located at or towards one or both of an inner and outer perimeter of the rotor.
In some embodiments the tapered portion of the permanent magnet overhangs the inner perimeter of the rotor.
In some embodiments the tapered portion does not extend more than half of the overall length of the magnet, and preferably not more than a third, or a quarter of the overall length.
In some embodiments the rotor is a moulded polymeric material.
In some embodiments the rotor is moulded from Bulk Moulding Compound.
In some embodiments the rotor comprises a rotor hub for connecting the rotor to a drive shaft of the washing machine, optionally wherein the rotor hub is made of steel.
In some embodiments the rotor hub is insert moulded into the polymeric material of the rotor.
In some embodiments the rotor hub comprises engagement features for engaging with the drive shaft.
In some embodiments the engagement features are provided in the form of internal splines configured to engage with corresponding splines on the drive shaft.
In some embodiments an annular backing ring for the magnets is moulded into the annular region of the rotor, optionally wherein the annular backing ring is made of steel.
In some embodiments the rotor has a profile such that the height of the rotor is greatest at or near the rotor hub, and decreases at or toward the annular region.
In some embodiments the annular region comprises radially extending ribs or legs.
In some embodiments the rotor comprises a reinforced region radially inward of the annular region about the rotor hub.
In some embodiments the reinforced region is substantially hollow and comprises a network of radially and/or circumferentially extending ribs.
In some embodiments the rotor comprises a lip about the exterior of the annular region.
In some embodiments the motor further comprises a fastening portion for attaching the stator to the body of the washing machine.
In some embodiments the fastening portion is formed as part of the stator itself.
In some embodiments the fastening portion is configured to engage a bearing housing of a drum of the washing machine, or a supporting structure extending outwardly from said bearing housing.
In some embodiments the fastening portion attaches the stator to rear of an outer drum of the washing machine.
In some embodiments the fastening portion is configured to receive between 3-6 fasteners for attaching the stator to the washing machine.
In some embodiments the fastening portion is configured to receive between 4-5 fasteners for attaching the stator to the washing machine.
In some embodiments the fastening portion comprises an outer annular region extending radially outward from the annular stator core, the outer annular region comprising apertures for receiving fasteners.
In some embodiments the fastening portion comprises an inner annular region extending radially inward of the annular stator core, the inner annular region comprising apertures for receiving fasteners.
In some embodiments the outer annular region is for attaching the fastening portion to the core of the stator and the inner annular region is for attaching the fastening portion to the washing machine.
In some embodiments the apertures of the inner annular region are arranged about a pitch circle having a pitch diameter between 120-140 mm, preferably between 126-134 mm.
In some embodiments at least one of the inner and outer annular regions are formed of steel.
In some embodiments the fastening portion is formed at least in part from an overmoulded polymeric material.
In some embodiments the polymeric material is Bulk Mounding Compound.
In some embodiments the fastening portion comprises vibration attenuation means configured to attenuate vibration of the stator during operation.
In some embodiments the vibration attenuation means comprise any one or more of apertures, slots, ribs or reinforced regions, such that the vibration of the stator during operation is absorbed by an elasticity of the fastening portion.
In some embodiments the vibration attenuation means comprise one or more radially or circumferentially extending slots.
In some embodiments the vibration attenuation means comprise one or more radially or circumferentially extending ribs.
In some embodiments the vibration attenuation means comprise one or more reinforced or thickened sidewalls.
In some embodiments the fastening portion has a conical profile.
In some embodiments the inner annular region of the fastening portion is provided by an inwardly extending flange of the annular stator core.
In some embodiments the fastening portion is an overmoulding of the stator core.
In some embodiments the fastening portion is an overmoulding of the stator core and stator coils.
In some embodiments the stator comprises one or more terminal connections, optionally wherein the terminal connections comprises one or more metallic pins, each pin retained in and extending from a plastic pocket.
In some embodiments the one or more terminal connections are located on an outer perimeter of the stator.
In some embodiments the rotor frame comprises one or more shaped holes through to the stator, said one or more holes adapted to receive tool for prizing the rotor frame away from the stator.
In a further aspect the invention may comprise a tool for use with the motor configured to prize the rotor frame away from the stator, wherein tool comprises a threaded shaft with a foot at the distal end, a handle at the proximal end and a nut located between the foot and the handle, wherein the nut is shaped to pass through the shaped hole of the rotor frame in a first orientation of the shaft and held within the shaped hole in a second orientation, wherein the tool is further configured such that in use the distal end of the shaft is inserted in the first orientation through one of the one or more shaped holes in the rotor frame and transitioned to the second orientation capturing the nut, wherein rotation of the handle and shaft about the captured nut causes the foot to move towards the underlying stator, away from the captured nut such that the rotor frame and stator are pushed apart.
In another aspect, in broad terms the invention comprises an axial flux permanent magnet synchronous motor for driving the load-containing drum of a laundry machine, comprising:
The optional embodiments previously described in respect of other aspects of the inventions apply as options to this aspect of the invention also.
In another aspect in broad terms the invention comprises a laundry machine comprising an outer cabinet, an outer drum suspended in the outer cabinet, and an inner drum housed within the outer drum and rotatable relative to the outer drum, wherein rotation of the inner drum is directly driven by an axial flux motor of any preceding embodiment.
In some embodiments a drive shaft transmits rotation from the rotor of the motor to the inner drum of the laundry machine.
In some embodiments the laundry machine comprises a bearing housing to house one or more bearings that support the drive shaft.
In some embodiments the outer drum comprises a polymeric end wall.
In some embodiments the bearing housing is held or moulded within the end wall.
In some embodiments the stator is adapted to fasten to the bearing housing or other metallic support.
In some embodiments the stator is fixed between the end wall and the rotor, with the rotor as the outermost part of the motor.
It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.
In this specification the term “comprising” means “consisting at least in part of”. When interpreting a statement in this specification and claims that includes “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted similarly.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the disclosure. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.
The disclosure may also be said broadly to comprise in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. Where, in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.
To those skilled in the art to which the disclosure relates, many changes in construction and widely differing embodiments and applications of the disclosure will suggest themselves without departing from the scope of the disclosure as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein which have known equivalents in the art to which this disclosure relates, such known equivalents are deemed to be incorporated herein as if individually set forth. The disclosure comprises the foregoing and also envisages constructions of which the following gives examples only.
The present embodiments relate to an Axial Flux Permanent Magnet Synchronous Motor (AF-PMSM or more generally axial flux motor). The motor 20 is for use in a direct drive laundry apparatus (“laundry machines”) 1.
The axial flux motor 20 will be described on its own. A general embodiment of an axial flux motor 20 will be described that could be used in a laundry machine 1. Variations to the general embodiment can provide exemplary embodiments, as will be described later. Use of the axial flux motor in a laundry machine will then be described.
Details of the axial flux motor 20 will now be described with reference to
As seen best in
As can be seen in
In some embodiments the top of each tooth 62 may have a chamfer 70 along each of the angled edges between the base 68 and the tip 69 where they meet the side wall 66. Seeing the insert of
The slot opening 63 has a width, which is preferably constant across the width of the annular core Wa, by virtue of the angle of adjacent tooth stems being such that the opposing sides 66 of neighbouring tooth stems 62 are parallel. In some embodiments the slot is between about 10 mm and about 20 mm in width.
The stator could be constructed in any suitable manner, such as constructed from laminations. For example, the stator core 60 may be constructed by winding strips of electrical steel in a spiral configuration. The strips of steel may have the profile of the stator yoke 61 and teeth 62 punched or cut into them prior to winding as shown in
The stator coil 101 may be wound onto the bobbin 102 in any suitable manner and can be electrically connected as shown in
When the stator coils 101 are energized, they generate magnetic poles of the stator which interact with the permanent magnetic poles of the rotor to cause to rotation. In some embodiments the ratio of the ratio of magnetic poles carried by the stator to magnetic poles carried by the rotor is 3:4. This magnetic pole ratio has been found to give good results in low vibration and noise performance of the axial flux motor. As shown in the Figures, in some embodiments the motor may have 27 stator coils and 36 magnetic poles provided by the permanent magnets of the rotor. However, that is by way of example only and should not be considered limiting. In some embodiments the number of electromagnetic symmetries of the motor is between 5 and 12 (the number of electromagnetic symmetries can be determined by finding the largest common factor between the number of rotor poles and the number of stator poles). For example, the motor may have 15 stator poles to 20 rotor poles, or 18 stator poles to 24 rotor poles, or 21 stator poles to 28 rotor poles, or 24 stator poles to 32 rotor poles, or 27 stator poles to 36 rotor poles, or 30 stator poles to 40 rotor poles, or 33 stator poles to 44 rotor poles, or 36 stator poles to 48 rotor poles. Of those options, there are embodiments where 15 stator poles to 20 rotor poles, 27 stator poles to 36 rotor poles, and 36 stator poles to 48 rotor poles are preferred.
The rotor 21 comprises a circular frame 137, an annular guide or backing ring 120 to which a plurality of permanent magnets 130 are attached, and a central hub 139 (with a knurled, toothed or splined aperture 140) for coupling to a drive shaft. The rotor frame 137 may be manufactured from steel plate or could alternatively be moulded from a plastics material such as BMC and may optionally include steel inserts for stiffness. The hub 139 may be fastened to the rotor frame 137, or, in the case of a plastics moulded rotor frame 137 the hub 139 may be insert moulded with the rotor frame 137.
Permanent magnets 130 are disposed evenly about the circumference of the rotor to provide a plurality of alternating magnetic poles as shown in
The magnets 130 may be glued or otherwise attached to the backing ring 120 (for example as seen in
In some embodiments the permanent magnets 130 are arranged about an annular region of the rotor 21 (for example overlying an annular backing ring 120), with the inner and outer diameter of the magnetic region (for example Di and Do in
Referring to
The rotor 21 and stator 22 are spaced relative to one another along the common axis 23, defining an air gap 27 between them, so that the magnetic flux path between the rotor magnets 130 and stator coils 101 is oriented in the axial direction. In some embodiments the air gap is between about 0.2 mm and 1.8 mm the axial direction. In some embodiments the air gap is between about 0.4 and 1.5 mm. In some embodiments the air gap is between 0.9 and 1.1 mm. In some embodiments the air gap is approximately 1.2 mm. The air gap may vary during operation of the motor, although it is desirable to maintain the air gap at a constant distance as far as possible. The motor performance and behaviour can change if the air gap varies too far outside of its specified range, therefore optimised assembly and careful tolerancing of part dimensions are needed to give acceptable control over the size of the air gap.
Some axial flux motors have a double rotor configuration, wherein there is a rotor axially spaced on either side of the stator, each rotor carrying its own plurality of permanent magnets. Conversely it can be possible to have a dual stator configuration, wherein there is a stator axially spaced on either side of a single rotor. However, in preferred embodiments of the present invention the axial flux motor is of single rotor configuration, i.e. it has only one rotor that is axially spaced from, and magnetically interacts, with only a single stator. In some embodiments, the overall height of the motor in the axial direction, with the rotor and stator concentrically mounted to define an air gap between them, is about 45 mm or less.
Various features of the embodiment above will now be described in further detail, each resulting in a variation or embodiment in its own right.
Each of the features described here in could be combined with any of the other features. For example any variation of the stator core could be provided with any variation of the rotor which could be provided with any variation of the magnets.
To provide maximal area of permanent magnetic material about the rotor (and hence maximal strength of the magnetic field), the magnets may be made with a tapered shape as described above and positioned adjacent one another to cover substantially an entire annular region of the rotor 21.
For some types of magnetic material it may be possible to mould the material to the desired tapered shape. Alternatively, a conventionally shaped piece of magnetic material (for example a sintered rectangular magnet) could be ground along its edges to achieve a tapered shape. The grinding process may typically require numerous different stages, and manual processing, in order to grind all of the different edge angles and chamfers; and thus can be relatively complex and expensive.
However, it has surprisingly been found that a substantially equivalent torque, efficiency and cogging performance can be achieved without using tapered magnets to cover substantially an entire annular region of the rotor 21. So in a variation, as seen in
The rectangular magnets 130 may be of a uniform thickness (as above), or alternatively (referring to
The hybrid shaped magnets of
In an embodiment the backing ring 120 of the rotor 21 is also formed of steel and is moulded into the frame. In an alternative embodiment, the central hub 139 is formed of the same polymeric material as the rotor frame 137 such that the rotor assembly is unitary.
As shown in
As shown in
As shown in
Such features provide for a rotor 21 with sufficient rigidity to avoid excessive vibration, and may help maintain the desired air gap between the rotor 21 and stator 22 during operation.
In some embodiments the fastening portion 22A may be configured to attach the stator 22 directly to the bearing housing structure 16 of the washing machine via the mounting holes 16A, or to some supporting structure extending outwardly from the bearing housing 16—such as a radially depending metallic support, frame or shroud (not shown) located about the central bearing housing 16. In some embodiments the fastening portion 22A may be configured to attach the stator 22 directly to a rear of an outer drum 5 of the washing machine.
In an embodiment the fastening portion 22A may be configured to receive fasteners (preferably between 3 and 6, and more preferably between 4 and 5) for attaching the stator 22 to the washing machine. For example, as shown in
As shown in
Additionally or alternatively, the fastening portion 22A of
The magnets on the rotor 21 strongly attract to the metallic core of the stator 22. For example, there may be a 60 kg magnetic force holding the rotor and stator together. In some circumstances (for example during manufacture, or for servicing) it may be necessary to separate the rotor from the stator.
In some embodiments, the rotor may have one or more “plus shaped” hole formations 21A. These appear as a rectangular hole from the topside of the rotor frame 137, and a rectangular recess at 90 degrees to the rectangular hole when viewed from the underside. In some embodiments, a tool 24 with a threaded shaft 25, a foot 26, a rectangular nut 27 and a handle 28 (as shown in
Four exemplary embodiments of an axial flux motor 20 will now be described, with reference to details of the rotor 21 and stator 22 dimensions and configurations.
An axial flux motor is described above can be used in a range of applications. In one example, it can be used to directly drive the load-containing drum in a front loading horizontal axis laundry machine, as described below. However the motor may alternatively be used to drive the load-containing drum in top or tilt access horizontal axis laundry washing machines, or top-loading, vertical axis laundry washing machines, or in laundry dryers or washer-dryers (which are conventionally horizontal access).
Referring to
In some embodiments the axial flux motor is suitable for driving the load-containing drum of a laundry machine, in terms of its size, power, electricity requirements, torque and/or speeds. For example, in some embodiments the axial flux motor provides a torque constant of between about 7 to about 12 Nm/A, which makes it suitable for driving a laundry drum containing between about 8 kg and about 20 kg loads of laundry (including loads which have absorbed liquid). The motor may need to drive rotation of the drum at speeds of up to 1500-2000 RPM during various stages of a washing and/or drying cycle.
Using an axial flux motor 20 such as described herein for a laundry machine has the potential provide an advantage over the prior art, including to deliver the following benefits:
The foregoing describes the invention including preferred forms thereof. Modifications and alterations as will be obvious to those skilled in the art may be made without departing from the scope of the invention, as defined in the claims.
Number | Date | Country | Kind |
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2021901990 | Jun 2021 | AU | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2022/056028 | 6/29/2022 | WO |