Patent Application
20250167645
The field of the disclosure relates generally to permanent magnet (PM) motors, and more particularly, the manufacture of PM motors using injection molding.
A PM motor is a type of electric motor that uses permanent magnets to provide a magnetic field, which may interact with one or more windings to produce motion. With respect to manufacturing PM motors, known systems and methods are disadvantaged in some aspects in meeting the needs of PM motor manufacturers and improvements are desired.
In one aspect, a system for manufacturing a rotor for a permanent magnet (PM) motor is provided. The system includes a mold configured to receive a rotor body including a plurality of rotor teeth and defining one or more rotor cavities. The system further includes a plurality of electromagnetic coils including a plurality of magnetic cores, each of the plurality of magnetic cores configured to align with a respective one of the plurality of rotor teeth, and a plurality of electromagnetic windings, wherein each of the electromagnetic windings is wound about at least one of the plurality of magnetic cores. The system further includes a controller configured to, after the rotor body is positioned within the mold, close the mold, after closing the mold, excite the plurality of electromagnetic coils, after exciting the plurality of electromagnetic coils, inject a magnetic material into the one or more rotor cavities, wherein the excited electromagnetic coils align the magnetic material into a desired magnetic orientation prior to solidification of the magnetic material, and after injecting the magnetic material, de-energize the plurality of electromagnetic coils.
In another aspect, a method for manufacturing a rotor for a PM motor is provided. The method is performed using a system including a mold configured to receive a rotor body including a plurality of rotor teeth and defining one or more rotor cavities and a plurality of electromagnetic coils including a plurality of magnetic cores, each of the plurality of magnetic cores configured to align with a respective one of the plurality of rotor teeth, and a plurality of electromagnetic windings, wherein each of the electromagnetic windings is wound about at least one of the plurality of magnetic cores. The method includes after the rotor body is positioned within the mold, closing the mold, after closing the mold, exciting the plurality of electromagnetic coils, after exciting the plurality of electromagnetic coils, injecting a magnetic material into the one or more rotor cavities, wherein the excited electromagnetic coils align the magnetic material into a desired magnetic orientation prior to solidification of the magnetic material, and after injecting the magnetic material, de-energizing the plurality of electromagnetic coils.
In another aspect, a controller for manufacturing a rotor for a PM motor is provided. The controller is in communication with a mold configured to receive a rotor body including a plurality of rotor teeth and defining one or more rotor cavities and a plurality of electromagnetic coils including a plurality of magnetic cores, each of the plurality of magnetic cores configured to align with a respective one of the plurality of rotor teeth, and a plurality of electromagnetic windings, wherein each of the electromagnetic windings is wound about at least one of the plurality of magnetic cores. The controller is configured to after the rotor body is positioned within the mold, close the mold, after closing the mold, excite the plurality of electromagnetic coils, after exciting the plurality of electromagnetic coils, inject a magnetic material into the one or more rotor cavities, wherein the excited electromagnetic coils align the magnetic material into a desired magnetic orientation prior to solidification of the magnetic material, and after injecting the magnetic material, de-energize the plurality of electromagnetic coils.
Example embodiments of the present disclosure include a system and corresponding method for manufacturing a permanent magnet (PM) motor. Manufacturing of PM electrical machines traditionally utilizes discrete magnets. Challenges involved in the manufacturing chain include a need for inventory control of parts of distinct dimensions and a need of gluing magnets in the rotor, resulting in a curing step of the part. Therefore, a process that enables the in-situ manufacturing of PMs directly in rotor cavities of the PM motor provides technical and economic advantages.
In example embodiments, the system includes a mold configured to receive a rotor body including a plurality of rotor teeth and defining one or more rotor cavities that can be filled with a magnetic material, such as a polymer with embedded magnetic particles. The system further includes a plurality of electromagnetic coils including a plurality of magnetic cores that align with a respective one of the plurality of rotor teeth, and a plurality of electromagnetic windings that are each wound about at least one of the plurality of magnetic cores, such that a desired magnetic filed pattern can be produced when current is supplied to the electromagnetic windings.
After the rotor body is positioned within the mold, the mold is closed, the electromagnetic coils are excited, after which the magnetic material is injected into the rotor cavities. The excited electromagnetic coils align the magnetic material into a desired magnetic orientation prior to solidification of the magnetic material. The electromagnetic coils are then de-energized after the magnetic material has sufficiently solidified, producing a PM rotor structure having the desired magnetic orientation for use in a PM motor.
Accordingly, system and method described herein provides a number of benefits over known systems and methods for manufacturing PM motors. One benefit is that an automated and simultaneous insertion of magnets in cavities reduces manufacturing time, reduces a chance of human error (e.g., with magnetic orientation), and eliminates a need of adhesives and the associated curing time. Another benefit is a simplification of supply chain, in that pellets (raw material for injection molding of numerous frame sizes) may be used instead of discrete magnets of distinct dimensions. Another benefit is flexibility of material selection, in that a change from one magnetic compound to a different one does not require any physical modification to the mold tooling. Another benefit is an ability to fully automate the process with no need for post-treatment, such as magnetization. Another benefit is modularity, in that a mold may be configured to accommodate rotors having different numbers of poles or different sizes of the rotor by adjusting the mold and/or the number of electromagnetic coils installed around the mold accordingly. Additionally, in some embodiments, the rotor may be assembled onto the shaft for (full/partial) injection of the magnetic material, which reduces a need for post-treatment handling.
In the example embodiment, system 100 further includes a plurality of electromagnetic coils 110. Each electromagnetic coil 110 includes a plurality of magnetic cores 112. Each of the magnetic cores 112 is configured to align with a respective one of the rotor teeth 106. Each electromagnetic coil 110 further includes a plurality of electromagnetic windings 114. Each electromagnetic winding 114 is wound about a respective magnetic cores 112, such that when electromagnetic winding 114 is supplied with an electric current and energized, the corresponding magnetic cores 112 becomes magnetized. In embodiments in which rotor body 104 defines a plurality of rotor poles, there is one electromagnetic coil 110 present for each rotor pole, and each electromagnetic coils 110 is configured to align with a respective one of the rotor poles when rotor body 104 is placed within mold 102. A shape of magnetic cores 112 complement a shape of rotor teeth 106 to provide efficient flux transfer to rotor cavities 108. For example, magnetic cores 112 may be shaped so that, as shown in
Electromagnetic windings 114 are formed from a conductive material such as, for example, aluminum or copper, and may be formed from wires or foils. In some embodiments, electromagnetic windings 114 may include electrical insulators on their surfaces. In embodiments in which more than one winding layer is present, insulation may be applied between the layers. The insulation may include films (e.g., polyethylene terephthalate (PET), paper-based (Nomex)) and/or liquid (thermal/UV) curable resins (e.g., epoxy and acrylates). Electromagnetic windings 114 are sufficiently thick to reduce losses and temperature rise and to limit the magnetic leakage passing between magnetic cores 112. Due to high currents (and current densities), there is non-trivial magnetic potential between magnetic cores 112.
In the example embodiment, system 100 further includes a controller 118. Controller 118 is in communication with and configured to control components of system 100, such as mold 102, electromagnetic coils 110, or other components described herein. It should be understood that, in some embodiments, one or more of the functions of controller 118 described below may be performed by components other than a single controller 118 (such as that shown in
In the example embodiment, controller 118 is configured to close the mold 102 after rotor body 104 is positioned within mold 102. For example, controller 118 may control actuators that cause mold 102 to close. By closing mold 102, a contained space is created into which hot magnetic material melt can be injected. In some embodiments, rotor body 104 is divided into axial segments, which may each be inserted into mold 102 at separate times. Rotor body 104 is positioned within mold 102 such that each rotor pole of rotor body 104 aligns with a corresponding electromagnetic coil 110, and each rotor tooth 106 aligns with a corresponding magnetic core 112.
In the example embodiment, controller 118 is configured to, after closing the mold, inject a magnetic material into rotor cavities 108. For example, controller 118 may control injectors that cause the magnetic material to move as a fluid or liquid (e.g., molten polymer including embedded magnetic particles) into mold 102 to fill rotor cavities 108. During injection, the magnetic material (e.g., polymer and magnetic particles) fills rotor cavities 108 under a certain pressure. The temperature of the magnetic material during injection is selected depending on the plastic matrix. In some embodiments, the injection period lasts from about 0.5 to about 10 seconds. Once injected into rotor cavities 108, the magnetic material may begin to cool and eventually solidify.
In the example embodiment, after closing mold 102, controller 118 is configured to excite electromagnetic coils 110 to align the magnetic material into a desired magnetic orientation prior to solidification of the magnetic material. For example, controller 118 may cause current to be supplied to electromagnetic windings 114, thereby magnetizing magnetic cores 112, which in turn produce a magnetic field that causes the fluid magnetic material to align into the desired magnetic orientation. Electromagnetic coils 110 may be excited prior to and/or during the injection of the magnetic material.
The magnetic flux density applied to all rotor cavities 108 must be higher than magnetic field required to fully orient the magnetic particles embedded in the magnetic material. In some embodiments, the magnetic field density may be, for example, about 1.8 tesla for iron-based constructions of magnetic cores 112 or about 2.2 tesla for iron-cobalt based constructions of magnetic cores 112. While the magnetic field is applied, the magnetic particles of the magnetic material rotate, aligning their magnetization axis with the magnetic field. This occurs when a viscosity of the polymer containing the magnetic particles, which is a function of temperature, is sufficiently low (i.e., the temperature is still sufficiently high). The magnetic field required for orienting is a function of temperature due to dependencies on magneto-crystalline anisotropy constants and saturation polarization, which controls intrinsic coercivity. The magnetic field generated by electromagnetic coils 110 is determined by the direct current applied during excitation. Applying a higher current results in a stronger magnetic field. In some embodiments, electromagnetic windings 114 are configured to carry a current density of about 15 amperes per square millimeter to about 25 amperes per square millimeter. A level of required orienting magnetic field magnitude depends on the specific magnetic material that is used. Examples of materials, ordered from lowest to highest magnetic field requirement, include polymer bonded ferrite, polymer bonded Sm—Fe—N, polymer bonded Neo, polymer bonded Mn—Bi, and polymer bonded Sm—Co. For the listed magnetic materials (not limited to them), the current applied during processing should be on an order of tens to hundreds of amps, provided that a relatively low number of turns of foil are used for electromagnetic windings 114. This approach also keeps coil excitation voltage requirements relatively low (e.g., under 48 volts), providing enhanced safety compared to more conventional wire implementations.
In the example embodiment, after exciting electromagnetic coils 110, controller 118 is configured to de-energize electromagnetic coils 110. In some embodiments, controller 118 de-energizes electromagnetic coils 110 after the magnetic material has solidified. Because the magnetic material solidifies while being held in the desired magnetic orientation by electromagnetic coils 110, the magnetic material maintains the desired magnetic orientation after solidifying, even when electromagnetic coils 110 are de-energized and the resulting orienting magnetic field is removed.
In some embodiments, after solidification of the magnetic material, controller 118 is further configured to open mold 102. For example, controller 118 may control actuators that cause mold 102 to close. In some embodiments, controller 118 is further configured to cause mold to eject rotor body 104 and the solidified magnetic material contained within rotor body 104. For example, controller 118 may control actuators that push or otherwise cause rotor body 104 to move outside of mold 102. Because solidified magnetic material is contained within rotor body 104, the mechanism used to eject rotor body 104 should be sufficiently strong to overcome any magnetic forces that resist removal of rotor body 104 from mold 102.
In the example embodiment, method 500 includes, after the rotor body is positioned within the mold, closing 502 the mold.
In the example embodiment, method 500 further includes, after closing the mold, exciting 504 the plurality of electromagnetic coils.
In the example embodiment, method 500 further includes, after exciting the plurality of electromagnetic coils, injecting 506 a magnetic material into the one or more rotor cavities, wherein the excited electromagnetic coils align the magnetic material into a desired magnetic orientation prior to solidification of the magnetic material.
In the example embodiment, method 500 further includes, after injecting the magnetic material, de-energizing 508 the plurality of electromagnetic coils.
In some embodiments, method 500 further includes, after solidification of the magnetic material, opening 510 the mold.
In some embodiments, method 500 further includes, after opening the mold, causing the mold to eject 512 the rotor body.
In some embodiments, the electromagnetic coils are de-energized after solidification of the magnetic material.
In some embodiments, the plurality of rotor teeth are curvilinear, and at least one of the one or more rotor cavities is defined between a pair of concentric rotor teeth of the plurality of rotor teeth.
In some embodiments, the rotor body is formed from a plurality of rotor laminations. In some such embodiments, at least one rotor lamination of the plurality of rotor laminations is rotationally skewed relative to another lamination of the plurality of rotor laminations.
In some embodiments, the rotor body defines a plurality of rotor poles, and each of the plurality of electromagnetic coils is configured to align with a respective one of the plurality of rotor poles.
Example embodiments of a system and method for manufacturing PM motors are described above in detail. The systems and methods are not limited to the specific embodiments described herein but, rather, components of the systems and/or operations of the methods may be utilized independently and separately from other components and/or operations described herein. Further, the described components and/or operations may also be defined in, or used in combination with, other systems, methods, and/or devices, and are not limited to practice with only the systems described herein.
At least one technical effect of the systems and methods described herein includes (a) enabling an automated insertion of permanent magnets into a rotor by utilizing a system that includes a mold and a plurality of electromagnetic coils that can align a magnetic material injected into the mold; (b) simplification of materials needed for insertion of permanent magnets into a rotor by using a molten magnetic material; and (c) increased modularity of systems for manufacturing PM motors by utilizing a automated system that includes a mold and a plurality of electromagnetic coils that can align a magnetic material injected into the mold, in which the numbers of electromagnetic coils and properties of the injected material can be controlled to achieve desired specifications of the rotor.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, 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 invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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 language of the claims.
