The field of the disclosure relates generally to electrical machines, and more particularly, to axial flux electric motors having an axially imbedded permanent magnet rotor and a coreless stator.
One of many applications for an electric motor is to propel fluids, for example to blow air with a fan or blower, as in heating or cooling, and, for example, for pumping a liquid, such as water, to recirculate water in a pool or spa. The electric motor may be configured to rotate an impeller within a pump or blower, which displaces a fluid, causing a fluid flow. Many gas burning appliances include an electric motor, for example, water heaters, boilers, pool heaters, space heaters, furnaces, and radiant heaters. In some examples, the electric motor powers a blower that moves air or a fuel/air mixture through the appliance. In other examples, the electric motor powers a blower that distributes air output from the appliance.
A common motor used in such systems is an alternating current (AC) induction motor. Typically, the AC induction motor is a radial flux motor, where the flux extends radially from the axis of rotation. Another type of motor that may be used in the application described above is an electronically commutated motor (ECM). ECMs may include, but are not limited to, brushless direct current (BLDC) motors, permanent magnet alternating current (PMAC) motors, and variable reluctance motors. Typically, these motors provide higher electrical efficiency than an AC induction motor. Some ECMs have an axial flux configuration in which the flux in the air gap extends in a direction parallel to the axis of rotation of the rotor.
Typically, such ECM motors include a stator core holding electrical windings that is formed of a magnetic material to carry the flux flow. For example, steel is commonly used to form such rotor cores. However, such steel cores may generate resistance to the flux flow during operation, resulting in reduced motor efficiency. Such efficiency losses resulting from resistance to the flux flow through the stator core are commonly referred to as “core loss.” To reduce or minimize core loss, some motors include a coreless stator, such as a printed circuit board (“PCB”) stator, that is not formed of a magnetic material. While such stators may reduce or eliminate efficiency losses due to core loss, coreless stators generally provide inefficient flux transmission with the rotor, thereby reducing the overall motor efficiency.
Some coreless ECM motors may utilize high energy rare earth magnets, such as neodymium magnets for example, to compensate for the reduction in flux transmission caused by the coreless stator. While such magnets may improve motor efficiency, these magnets are often very expensive and are obtainable from only very limited locations. Obtaining improved motor efficiency in a motor having a coreless stator without the need for rare earth magnets is desired.
In one embodiment, an axial flux motor is provided. The axial flux motor includes a housing and a rotor assembly rotatably secured to the housing. The rotor assembly includes a body defining an axis of rotation thereof, the body having first and second opposed faces, a plurality of rotor poles including a first rotor pole and a second rotor pole. The first rotor pole and the second rotor pole cooperatively defining an axially extending pocket circumferentially therebetween. The rotor assembly further includes a plurality of spaced apart magnets extending from the first face, a first magnet of the plurality of magnets being positioned within the axially extending pocket. The axial flux motor further includes a coreless stator assembly fixedly secured to the housing, the coreless stator assembly including a supporting platform and a plurality of coils attached on the supporting platform.
In another embodiment, an axial flux motor is provided. The axial flux motor includes a housing and a rotor rotatably secured to the housing. The rotor includes a body defining an axis of rotation thereof, the body having first and second opposed faces. The rotor further includes a plurality of rotor poles including a first rotor pole and a second rotor pole. The axial flux motor further includes a plurality of spaced apart magnets extending from the first face. A first magnet of the plurality of magnets being positioned circumferentially between, and in contact with, the first rotor pole and the second rotor pole. The axial flux motor further includes a stator fixedly secured to the housing. The stator including a supporting platform formed of a non-magnetic material and a plurality of coils attached on the supporting platform.
In yet another embodiment, an axial flux motor is provided. The axial flux motor includes a housing and a rotor assembly rotatably secured to the housing. The rotor assembly includes a body defining an axis of rotation thereof, the body having first and second opposed faces. The rotor assembly further includes a plurality of rotor poles including a first rotor pole and a second rotor pole. The axial flux motor further includes a plurality of spaced apart magnets extending from the first face. A first magnet of the plurality of magnets is positioned circumferentially between the first rotor pole and the second rotor pole. The axial flux motor further includes a coreless stator assembly fixedly secured to the housing. The coreless stator assembly includes a supporting platform defining a mounting aperture and a bobbin assembly including an electrical winding and a bobbin holding the electrical winding. The bobbin assembly further includes a mounting post extending from the bobbin into the mounting aperture to secure the bobbin assembly to the supporting platform.
As shown in
Rotor assembly 18 is rotatably secured to housing 16, and more specifically, is rotatable within first bearing assembly 20 and second bearing assembly 22 about an axis of rotation 36. It should be appreciated that other support schemes may be possible for supporting the rotating rotor assembly within the housing. For example, a single bearing assembly (not shown) may be used and may be located where the first bearing assembly or where the second bearing assembly is located.
Referring to
The rotor assembly 18 also has a plurality of spaced apart magnets 34. Each of the plurality of magnets 34 is matingly fitted to one of a plurality of pockets 31 (defined between adjacent laminations 48). As shown in
While the sheets may form a contiguous core 30 and the magnets 34 may be fitted to the core 30, it should be appreciated that some of the sheets may be combined to form a pole 19 with the sheets of each pole being spaced from the sheets of the other poles. In such a configuration a bonding material, such as a resin may be used to interconnect all the components forming the rotor assembly 18. In such a configuration, the core 30 may include a central portion 21. The central portion 21 may support a central rotor shaft 32 and the poles 19 and the magnets 34 may extend from core outer periphery 43 to the central portion 21 of the core 30.
The rotor assembly 18 may be manufactured by placing the poles 19, the magnets 34 and the shaft 32 in a resin mold (not shown) and injecting resin in to mold, bonding the magnets 34, the shaft 32 and the poles 19 together to form the rotor assembly 18. In such embodiments, the shaft 32 is not placed in the mold and, rather, may be later assembled into the rotor assembly 18
As shown in
Referring to
In the example embodiment, rotor 30 includes a plurality of axial pockets 31. For example, as shown in
In the example embodiment, the magnets 34 are positioned against the sides 51 and 53 of rotor poles 19. The first and second ends 55 and 56 (shown in
In the example embodiment, rotor 30 includes a plurality of rotor poles 19 each having an outer surface along rotor outer periphery 43 and extending radially inwardly to inner wall 68. As shown in
Although illustrated as generally trapezoidal in
Referring back to
In the example embodiment, the design of rotor 30 utilizes lower-cost magnets, yet achieves the power densities and high efficiency of machines using higher-cost magnets such as neodymium magnets. In the example embodiment, increased efficiency and power density of machine 10 is obtained by increasing the flux produced by rotor 30. That is, the flux output of rotor 30 is directly proportional to the depth of the magnets 34. The increased flux generation is facilitated by magnets 34 having a minimum depth, which is defined by the equation (1):
=2*N*D1*R3*Br (eq. 1);
wherein Φ represents the flux output of rotor 30, N represents the number of rotor poles 19, D1 represents the axial depth of the magnets 34, R3 represents the radial length of the magnets 34, and Br represents the remnant flux density of the magnets 34. As a result, for a given and/or desired flux output of the rotor, a minimum axial depth of the magnets 34 may be determined by the equation (2), provided below:
In the example embodiment, rotor 30 facilitates increased flux production resulting in improved efficiency and power density due to an elongated axial depth D1 of magnets 34. In the example embodiment, depth D1 may be variably selected to adjust the power output of machine 10 while maintaining a constant rotor size (a constant radial length R3 and a constant number of poles 19). For example, decreasing depth D1 lowers motor power output and increasing depth D1 increases motor output. For example, in the example embodiment, motor power output of axial flux machine 10 is approximately one horsepower and magnets 34 have an axial depth D1 of approximately one inch. In other embodiments, the size of the rotor 30 may also be adjusted to provide greater horsepower. For example, for larger horsepower motors at least one of the radial length R3 and the axial depth D1 of the magnets may be increased. As such, machine 10 may be designed for a specific power output application without additional tooling costs to adjust the outer diameter of the rotor and/or stator.
While the axial flux motor of the present disclosure may be provided with poles that are generally trapezoidal, other shapes are anticipated and may function similarly. The use of rectangular poles (e.g., as shown in
In the example embodiment, stator assembly 24 is a coreless stator assembly. As used herein, the term “coreless stator” means that the stator does not include a magnetic core holding the stator windings or bobbin assembly 86 in place within the motor housing 16. Rather, in the example embodiment, bobbin assembly 86 is directly attached to stator plate 90, which is formed of a non-magnetic, non-conducting material. In particular, in the example embodiment the stator plate 90 is formed of a polymer and/or plastic material, though in alternative embodiments, the stator plate 90 may be formed of any suitable a non-magnetic, non-conducting material. For example, in some alternative embodiments stator plate 90 is formed of a non-ferrous metal such as aluminum. In some embodiments, as described in greater detail with respect to
Bobbin assembly 86 generally includes a plurality of bobbins 87 coupled to a control board 88. Although twelve bobbins 87 are illustrated, bobbin assembly 86 may include any number of bobbins that enables machine 10 to function as described herein. Each bobbin 87 includes an opening 89. In the example embodiment, bobbin assembly 86 also includes electrical winding 97 that includes a plurality of coils 98. In the example embodiment, winding 97 is made up of twelve coils 98 and creates a twelve-pole stator.
In the example embodiment, coils 98 are wound around bobbins 87, and each coil 98 includes two ends, a start and a finish to the coil. Bobbins 87 are coupled electrically coupled to control board 88. In the example embodiment, control board 88 is a printed circuit board (PCB), and each end of each of coil 98 is coupled to control board 88 using an insulation displacement terminal (not shown) designed for directly soldering into control board 88. Alternatively, any other suitable connector may be used that enables the plurality of bobbins 87 to be coupled to control board 88. In the example embodiment, control board 88 includes a wiring connector 128 for directly connecting control board 88 to a motor control board (not shown). In an alternative embodiment, control board 88 is incorporated within a motor control board, thereby eliminating redundant mounting and connectors.
In the example embodiment, stator plate 90 has a disc shape including an outer circumferential edge 92 and an inner rim 94 defining an opening 96. As shown in
In the example embodiment, bobbins 87 are configured to be coupled to, or more specifically, mounted on stator plate 90. In particular bobbins 87 each include a first end 102 oriented to face rotor assembly 18 (e.g., as shown in
In some embodiments, mounting posts 106 are configured to fasten to stator plate 90 by one or more additional fastening elements (not shown), such as a nut, bolt, or other threaded interface between mounting posts 106 and stator plate 90. In other embodiments, mounting posts 106 and or bobbins 87 may be bonded (e.g., via an adhesive or welding) to stator plate 90. In further embodiments, mounting posts 106 are configured for an interference and/or friction fit within mounting apertures 108 to secure bobbins 87 to stator plate 90. For example, and without limitation, in some embodiments, mounting posts 106 may include a wedge tip (not shown) at distal ends of the mounting posts 106 which may engage a slot (not shown) defined within mounting apertures 108. In yet further embodiments, bobbins 87 may be attached to stator plate 90 in any manner that enables electric machine 10 to function as described herein.
The coreless stator assembly 24 in combination with the rotor assembly allows provides a higher level of electrical efficiency compared with conventional stators which include a ferromagnetic core. In particular, the electrical efficiency of a motor is conventionally defined as a ratio of the mechanical power output of the motor to the electrical power input to the motor. Example motors according to the embodiments described herein may have an electrical efficiency that is greater than or equal to 85%, greater than or equal to 90%, or greater than or equal to 95%. The example electrical machine described with respect to
In the example embodiment, stator assembly 300 is substantially the same as stator assembly 104 described in U.S. Pat. No. 10,818,427, which is hereby incorporated by reference in its entirety, except as described differently below. In particular, in the example embodiment stator assembly 300 is a coreless stator. In other words, in the example embodiment, body 302 and teeth 304 of stator assembly 300 are formed of a non-magnetic, non-conducting material. In particular, in the exemplary embodiment, body 302 and teeth 304 are formed of a polymer material, though in other embodiments body 302 and teeth 304 may be formed of any suitable non-magnetic, non-conducting material.
Each bobbin assembly 308 includes a conduction coil 310 positioned on a bobbin 312 that is configured to support conduction coil 310. Each bobbin 312 includes a body portion 314 having a first end 316 and a second end 318. Specifically, each conduction coil 310 is wrapped around or coupled about body portion 314 of bobbin 312 between first end 316 and second end 318. Additionally, body portion 314 defines a central opening 320 that receives one stator tooth 304. Bobbins 312 are coupled to every other stator tooth 304 of stator assembly 300 such that conduction coil 310 extends about stator tooth 304 and through slots 306. In particular, each conduction coil 310 extends through slots 306 on each side of the respective stator tooth 304. In the example embodiment, bobbins 312 and conduction coils 310 are positioned on every other stator tooth 304 and between circumferentially adjacent teeth 304. In particular, bobbins 312 are coupled to supporting platform 301 such that a first tooth 305 extends through central opening 320, a second tooth 307 engages a first side 311 of bobbin 312, and a third tooth 309 engages a second opposed side 313 of bobbin 312.
In the example embodiment, stator assembly 300 also includes a plurality of insulation members 322 to insulate components of stator assembly 300, such as annular body 302 and stator teeth 304, from electric current flowing through conduction coil 310. Insulation members 322 are made from a material that is substantially nonconductive. For example, in some embodiments, insulation members 322 are plastic and/or any other material suitable for use as a nonconductive barrier. In some embodiments, at least in part to the body 302 being formed of a non-magnetic, non-conductive material, no insulation members 322 are provided and bobbins 312 are positioned in direct contact with stator teeth 304.
In the example embodiment, each bobbin 312 also includes an extension tab 326 formed on one of first end 316 or second end 318 such that extension tab 326 extends radially beyond a radially inner end or a radially outer end of conduction coil 310. In the example embodiment, extension tab 326 is formed on first end 316 such that extension tab 326 extends beyond radially outer end of conductor coil 112. In such a configuration, extension tab 326 also extends beyond a radially outer end of second end 318. In the example embodiment extension tab 326 extends radially outward a predetermined distance to cover a wire lead 324 of stator assembly 300. More specifically, extension tab 326 extends radially beyond wire lead 324. In the example embodiment, extension tab 326 includes an opening 328 defined therethrough. Opening 328 is substantially radially aligned with central opening 320 of body portion 314 and is positioned radially outward of conductor coil 112. In the example embodiment, opening 328 is configured to receive a lead tie (not shown) of stator assembly 300 to secure wire lead 324 to bobbin 312.
Described herein are example methods and systems for axial flux machines. The axial flux machines include a rotor having axially embedded permanent magnets and a coreless stator. The coreless stator allows for improved efficiency of the axial flux machine by reducing and/or eliminating core loss in the stator. The axially embedded rotor design enables the use of lower-cost ferrite magnets with the coreless stator, while achieving the power densities and higher efficiency of other rotor designs that use higher-cost neodymium magnets.
Example embodiments of the axial flux electric machine assembly are described above in detail. The electric machine and its components are not limited to the specific embodiments described herein, but rather, components of the systems may be utilized independently and separately from other components described herein. For example, the components may also be used in combination with other machine systems, methods, and apparatuses, and are not limited to practice with only the systems and apparatus as described herein. Rather, the example embodiments can be implemented and utilized in connection with many other applications.
Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.