Power tool including a memory motor

Abstract

A power tool may include a housing. A power tool may include a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings, and a rotor including a first magnet positioned a first distance from a center of rotation of the rotor and a second magnet positioned a second distance from the center of the rotation of the rotor, wherein the first magnet is made of a rare earth material and the second magnet is a low-coercive-force magnet.

Description

POWER TOOL INCLUDING A MEMORY MOTORRELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 604,387, filed November 30, 2023, and U.S. Provisional Patent Application No. 63 / 612,128, filed December 19, 2023, the entire content of each of which is hereby incorporated by reference.FIELD

[0002] This disclosure relates to power tools.SUMMARY

[0003] Power tool described herein include a housing and a motor assembly positioned within the housing. The motor assembly includes a stator with winding slots that receive stator windings, and a rotor including a first magnet positioned a first distance from a center of the rotation of the rotor and a second magnet positioned a second distance from the center of the rotation of the rotor. The first magnet is made of a rare earth material and the second magnet is a low-coercive-force magnet.

[0004] In some aspects, the rotor further includes an outer rotor portion and an inner rotor portion, and the outer rotor portion and the inner rotor portion are connected to one another by a rotor rib that extends from the outer rotor portion to the inner rotor portion in a radial direction away from the center of rotation of the rotor.

[0005] In some aspects, the rotor further includes an air slot located between the outer rotor portion and the inner rotor portion.

[0006] In some aspects, the first magnet extends a first distance into the air slot and the second magnet extends In some aspects, the power tool further includes a second distance into the air slot.

[0007] In some aspects, the rotor further includes a magnet housing portion that separates the first magnet from the second magnet.

[0008] In some aspects, the magnet housing portion includes a first thickness and a second thickness, the first thickness being greater than the second thickness.

[0009] In some aspects, the first magnet includes a first arm extending a first arm length away from the first magnet at between approximately 30 degrees and approximately 45 degrees.

[0010] In some aspects, the first magnet includes a second arm length extending away from the first magnet, and the second arm length is approximately half the first arm length.

[0011] In some aspects, the first magnet includes a first magnet portion and second magnet portion, the first magnet portion including a rare earth material and the second magnet portion including a low-coercive-force magnet.

[0012] Power tools described herein include a housing and a motor assembly positioned within the housing. The motor assembly includes a stator with winding slots that receive stator windings and a rotor. The rotor includes a first magnet including first arm having a first arm length and a first arm width, and a second magnet including second arm having a second arm length and a second arm width. The first arm extends the first arm length away from the first magnet at approximately a 45 degree angle in a radial direction away from a center of rotation of the rotor. The first magnet is made of a rare earth material and the second magnet is a low- coercive-force magnet.

[0013] In some aspects, the rotor further includes an outer rotor portion and an inner rotor portion, and an air slot located between the outer rotor portion and the inner rotor portion, wherein the first magnet extends a first distance into the air slot and the second magnet extends a second distance into the air slot, and wherein the outer rotor portion and the inner rotor portion are connected to one another by a rotor rib that extends from the outer rotor portion to the inner rotor portion in the radial direction away from the center of rotation of the rotor.

[0014] In some aspects, the rotor further includes a magnet housing portion that separates the first magnet from the second magnet, the magnet housing portion including a first thickness and a second thickness, the first thickness being greater than the second thickness.

[0015] In some aspects, the first magnet includes a third arm length extending away from the first magnet, and the third arm length is approximately half the first arm length.

[0016] In some aspects, the first magnet includes a first magnet portion and second magnet portion, the first magnet portion including a rare earth material and the second magnet portion including a low-coercive-force magnet.

[0017] Power tools described herein include a housing and a motor assembly positioned within the housing. The motor assembly includes a stator with winding slots that receive stator windings and a rotor. The rotor includes a first air slot, a first magnet configured in a spoke configuration, and a second magnet including an inner radial length and an outer radial length. The inner radial length is positioned a first radial distance away from a center of rotation of the rotor, and the outer radial length is positioned a second radial distance away from the center of rotation of the rotor. The first magnet is separated from the second magnet by a second air slot. The first magnet is made of a rare earth material and the second magnet is a low-coercive-force magnet.

[0018] In some aspects, the first air slot separates the first magnet from an outer rib of the rotor.

[0019] In some aspects, the rotor further includes a plurality of first magnets and a plurality of second magnets, wherein each of the plurality of second magnets is separated by respective second air slots.

[0020] In some aspects, rotor further includes an inner rotor portion, an outer rotor portion, and a plurality of second air slots, wherein the second magnet extends a magnet length from the inner rotor portion to the outer rotor portion, and wherein a first portion of the second magnet is exposed to a first of a plurality of second air slots and a second portion of the second magnet is exposed to a second of the plurality of second air slots.

[0021] In some aspects, the outer radial length is greater than the inner radial length.

[0022] In some aspects, the power tool further includes the rotor includes six first magnets configured in the spoke configuration.

[0023] Before any embodiments are explained in detail, it is to be understood that the embodiments are not limited in application to the details of the configurations and arrangements of components set forth in the following description or illustrated in the accompanying drawings. The embodiments are capable of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof are meant to encompass the items listedthereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings.

[0024] Unless the context of their usage unambiguously indicates otherwise, the articles “a,” “an,” and “the” should not be interpreted as meaning “one” or “only one.” Rather these articles should be interpreted as meaning “at least one” or “one or more.” Likewise, when the terms “the” or “said” are used to refer to a noun previously introduced by the indefinite article “a” or “an,” “the” and “said” mean “at least one” or “one or more” unless the usage unambiguously indicates otherwise.

[0025] In addition, it should be understood that embodiments may include hardware, software, and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic-based aspects may be implemented in software (e.g., stored on non-transitory computer-readable medium) executable by one or more processing units, such as a microprocessor and / or application specific integrated circuits (“ASICs”). As such, it should be noted that a plurality of hardware and software based devices, as well as a plurality of different structural components, may be utilized to implement the embodiments. For example, “servers,” “computing devices,” “controllers,” “processors,” etc., described in the specification can include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and various connections (e.g., a system bus) connecting the components.

[0026] Relative terminology, such as, for example, “about,” “approximately,” “substantially,” etc., used in connection with a quantity or condition would be understood by those of ordinary skill to be inclusive of the stated value and has the meaning dictated by the context (e.g., the term includes at least the degree of error associated with the measurement accuracy, tolerances [e.g., manufacturing, assembly, use, etc.] associated with the particular value, etc.). Such terminology should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4”also discloses the range “from 2 to 4”. The relative terminology may refer to plus or minus a percentage (e.g., 1%, 5%, 10%) of an indicated value.

[0027] It should be understood that although certain drawings illustrate hardware and software located within particular devices, these depictions are for illustrative purposes only. Functionality described herein as being performed by one component may be performed by multiple components in a distributed manner. Likewise, functionality performed by multiple components may be consolidated and performed by a single component. In some embodiments, the illustrated components may be combined or divided into separate software, firmware and / or hardware. For example, instead of being located within and performed by a single electronic processor, logic and processing may be distributed among multiple electronic processors. Regardless of how they are combined or divided, hardware and software components may be located on the same computing device or may be distributed among different computing devices connected by one or more networks or other suitable communication links. Similarly, a component described as performing particular functionality may also perform additional functionality not described herein. For example, a device or structure that is “configured” in a certain way is configured in at least that way but may also be configured in ways that are not explicitly listed.

[0028] Accordingly, in the claims, if an apparatus, method, or system is claimed, for example, as including a controller, control unit, electronic processor, computing device, logic element, module, memory module, communication channel or network, or other element configured in a certain manner, for example, to perform multiple functions, the claim or claim element should be interpreted as meaning one or more of such elements where any one of the one or more elements is configured as claimed, for example, to make any one or more of the recited multiple functions, such that the one or more elements, as a set, perform the multiple functions collectively.

[0029] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 illustrates a perspective view of a power tool, according to some embodiments.

[0031] FIG. 2 illustrates a block diagram of a control system of the power tool of FIG. 1, according to some embodiments.

[0032] FIG. 3 illustrates a battery pack for use with the power tool of FIG. 1, according to some embodiments.

[0033] FIG. 4 illustrates a block diagram of a control system of the battery pack of FIG. 3, according to some embodiments.

[0034] FIG. 5 illustrates a memory motor, according to some embodiments.

[0035] FIG. 6 illustrates a memory motor, according to some embodiments.

[0036] FIG. 7 illustrates a memory motor, according to some embodiments.

[0037] FIG. 8 illustrates a memory motor, according to some embodiments.

[0038] FIG. 9 illustrates a memory motor, according to some embodiments.

[0039] FIG. 10 illustrates a memory motor, according to some embodiments.

[0040] FIG. 11 graphically illustrates performance of various motors, according to some embodiments.DETAILED DESCRIPTION

[0041] A memory motor is a category of permanent magnet (PM) machines with distinctive characteristics and capabilities. In particular, the magnetic field flux density of a memory motor rotor magnet may be adjusted, and the magnet will retain the adjusted level of magnetic field flux density. In some instances, memory motors may be constructed as pole-changing memory motors (PCMM) or as variable flux memory motors (VFMM). In contrast, a traditional internal permanent magnet (IPM) machine requires a separate demagnetizing current in order to weaken the magnetic field during operation. For instance, in some examples, memory motors include low-coercive-force (LCF) magnets, which enable field weakening without the need for constant field weakening currents such as those required in IPM machines. Because memory motors do not rely on a constant field weakening current, they offer advantages over an IPM by reducing motor complexity and potential energy losses. For example, the memory motor may provide a wider operating range, and / or improve power and efficiency at light to medium load range. Embodiments provided herein detail the advantages and applications of a memory motor in apower tool. In some embodiments, memory motors can be used in place of a motor having, for example, an outer stator diameter of 50mm or greater. In other embodiments, memory motors can be used in place of a motor having, for example, an outer stator diameter of 40mm or greater. When the LCF magnets are demagnetized, the memory motor is capable of, for example, approximately 30% higher speeds. When the LCF magnets are magnetized the memory motor is capable of, for example, approximately 30% higher torque. The LCF magnets can be magnetized by injecting a high current pulse into a motor drive signal. The short pulse of high current is sufficient to control magnetization of the LCF magnets.

[0042] FIG. 1 illustrates a power tool 100 including a motor, such as a memory motor (also referred to as a motor assembly). The power tool 100 is, for example, a hammer drill including a housing 102. Although FIG. 1 illustrates a hammer drill, in some embodiments, the components described herein are incorporated into other types of power tools including drill-drivers, impact drivers, impact wrenches, angle grinders, circular saws, reciprocating saws, plate compactors, core drills, string trimmers, leaf blowers, vacuums, or other applicable applications that may use field weakening for motor operation. The housing 102 includes a handle portion 104 and motor housing portion 106. The power tool 100 further includes an output driver 108 (illustrated as a chuck), a trigger 110, and a battery pack interface 112. The battery pack interface 112 is configured to mechanically and electrically connect to or receive a power tool battery pack. In a memory motor power tool, such as power tool 100, switching elements are selectively enabled and disabled by control signals from a controller to selectively apply power from a power source (e g., battery pack) to drive a memory motor.

[0043] FIG. 2 illustrates a control system 200 for the power tool 100. The control system 200 includes a controller 202. The controller 202 is electrically and / or communicatively connected to a variety of modules or components of the power tool 100. For example, the illustrated controller 202 is electrically connected to a motor 204, a battery pack interface 206, a trigger switch 208 (connected to a trigger 210), one or more sensors or sensing circuits 212, one or more indicators 214, a user input module 216, a power input module 218, an inverter bridge or FET switching module 220 (e.g., including a plurality of switching FETs), and gate drivers 224 for driving the FET switching module 220. In some embodiments, motor 204 is a memory motor. The controller 202 includes combinations of hardware and software that are operable to,among other things, control the operation of the power tool 100, monitor the operation of the power tool 100, activate the one or more indicators 214 (e.g., an LED), etc.

[0044] The controller 202 includes a plurality of electrical and electronic components that provide power, operational control, and protection to the components and modules within the controller 202 and / or the power tool 100. For example, the controller 202 includes, among other things, a processing unit 226 (e.g., a microprocessor, a microcontroller, an electronic controller, an electronic processor, or another suitable programmable device), a memory 228, input units 230, and output units 232. The processing unit 226 includes, among other things, a control unit 234, an arithmetic logic unit (“ALU”) 236, and a plurality of registers 238, and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 226, the memory 228, the input units 230, and the output units 232, as well as the various modules or circuits connected to the controller 202 are connected by one or more control and / or data buses (e.g., common bus 240). The control and / or data buses are shown generally in FIG. 2 for illustrative purposes. The use of one or more control and / or data buses for the interconnection between and communication among the various modules, circuits, and components would be known to a person skilled in the art in view of the invention described herein.

[0045] In some embodiments, the controller 202 is configured to control the gate drivers 224 to drive the motor 204 using a sensored or sensorless field-oriented control (“FOC”) motor control technique.

[0046] The memory 228 is a non-transitory computer readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area can include combinations of different types of memory, such as a ROM, a RAM (e.g., DRAM, SDRAM, etc ), EEPROM, flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic memory devices. The processing unit 226 is connected to the memory 228 and executes software instructions that are capable of being stored in a RAM of the memory 228 (e.g., during execution), a ROM of the memory 228 (e.g., on a generally permanent basis), or another non-transitory computer readable medium such as another memory or a disc. Software included in the implementation of the power tool 100 can be stored in the memory 228 of the controller 202. The software includes, for example, firmware, one or moreapplications, program data, filters, rules, one or more program modules, and other executable instructions. The controller 202 is configured to retrieve from the memory 228 and execute, among other things, instructions related to the control processes and methods described herein. In other constructions, the controller 202 includes additional, fewer, or different components.

[0047] The battery pack interface 206 includes a combination of mechanical components (e.g., rails, grooves, latches, etc.) and electrical components (e.g., one or more terminals) configured to and operable for interfacing (e.g., mechanically, electrically, and communicatively connecting) with a battery pack. For example, power provided by a battery pack 300 (see FIG. 3) to the power tool 100 is provided through the battery pack interface 206 to the power input module 218. The power input module 218 includes combinations of active and passive components to regulate or control the power received from the battery pack 300 prior to power being provided to the controller 202. The battery pack interface 206 also supplies power to the FET switching module 220 to be switched by the switching FETs to selectively provide power to the motor 204. The battery pack interface 206 also includes, for example, a communication line 242 for providing a communication line or link between the controller 202 and the battery pack 300.

[0048] The sensing circuit 212 include one or more current sensors, one or more speed sensors, one or more Hall effect sensors, one or more temperature sensors, etc. The indicators 214 include, for example, one or more light-emitting diodes (“LEDs”). The indicators 214 can be configured to display conditions of, or information associated with, the power tool 100. For example, the indicators 214 are configured to indicate measured electrical characteristics of the power tool 100, the status of the power tool, the status the motor 204, etc. The user input module 216 is operably coupled to the controller 202 to, for example, select a forward mode of operation or a reverse mode of operation, a torque and / or speed setting for the power tool 100 (e.g., using torque and / or speed switches), etc. In some embodiments, the user input module 216 includes a combination of digital and analog input or output devices required to achieve a desired level of operation for the power tool 100, such as one or more knobs, one or more dials, one or more switches, one or more buttons, etc.

[0049] FIG. 3 illustrates a battery pack 300. The battery pack 300 includes a housing 302 and an interface portion 304 for connecting the battery pack 300 to a power tool, such as the power tool 100.

[0050] FIG. 4 illustrates a control system for the battery pack 300. The control system includes a controller 400. The controller 400 is electrically and / or communicatively connected to a variety of modules or components of the battery pack 300. For example, the illustrated controller 400 is connected to one or more battery cells 402 and an interface 404 (e.g., the interface portion 304 of the battery pack 300 illustrated in FIG. 3). The controller 400 is also connected to one or more voltage sensors or voltage sensing circuits 406, one or more current sensors or current sensing circuits 408, and one or more temperature sensors or temperature sensing circuits 410. The controller 400 includes combinations of hardware and software that are operable to, among other things, control the operation of the battery pack 300, monitor a condition of the battery pack 300, enable or disable charging of the battery pack 300, enable or disable discharging of the battery pack 300, etc.

[0051] The controller 400 includes a plurality of electrical and electronic components that provide power, operational control, and protection to the components and modules within the controller 400 and / or the battery pack 300. For example, the controller 400 includes, among other things, a processing unit 412 (e.g., a microprocessor, a microcontroller, an electronic processor, an electronic controller, or another suitable programmable device), a memory 414, input units 416, and output units 418. The processing unit 412 includes, among other things, a control unit 420, an ALU 422, and a plurality of registers 424, and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 412, the memory 414, the input units 416, and the output units 418, as well as the various modules or circuits connected to the controller 400 are connected by one or more control and / or data buses (e.g., common bus 426). The control and / or data buses are shown generally in FIG. 4 for illustrative purposes. The use of one or more control and / or data buses for the interconnection between and communication among the various modules, circuits, and components would be known to a person skilled in the art in view of the embodiments described herein.

[0052] The memory 414 is a non-transitory computer readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area can include combinations of different types of memory, such as a ROM, a RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic memory devices. The processing unit 412 is connected to the memory 414 and executes software instructions that are capable of being stored in a RAM of the memory 414 (e.g., during execution), a ROM of the memory 414 (e.g., on a generally permanent basis), or another non-transitory computer readable medium such as another memory or a disc. Software included in the implementation of the battery pack 300 can be stored in the memory 414 of the controller 400. The software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. The controller 400 is configured to retrieve from the memory 414 and execute, among other things, instructions related to the control processes and methods described herein. In other constructions, the controller 400 includes additional, fewer, or different components.

[0053] The interface 404 includes a combination of mechanical components (e.g., rails, grooves, latches, etc.) and electrical components (e.g., one or more terminals) configured to and operable for interfacing (e.g., mechanically, electrically, and communicatively connecting) the battery pack 300 with another device (e.g., a power tool, a battery pack charger, etc.). For example, the interface 404 is configured to communicatively connect to the controller 400 via a communications line 428.

[0054] FIG. 5 illustrates a memory motor 500, according to some embodiments. The motor 500 includes a stator 505 and a plurality of stator winding slots 510 that receive stator windings. The plurality of stator winding slots 510 are configured to receive a plurality of windings, wound around the stator teeth 515. The motor 500 also includes a rotor 520. The rotor 520 is configured to receive a first magnet 525 and a second magnet 530. In some examples, the first magnet 525 is referred to as an inner magnet, and the second magnet 530 is referred to as an outer magnet. The first magnet 525 is positioned a first distance 555 from a center of rotation 560 of the rotor 520. The second magnet 530 is positioned a second distance 565 from the center of rotation 560 of the rotor 520. In some examples, the second distance 565 is greater than first distance 555.

[0055] The first magnet 525 includes a first magnet width 535 and a first magnet length 540. The second magnet 530 includes a second magnet width 545 and a second magnet length 550. In some examples, the first magnet width 535 is greater than the second magnet width 545. In some examples, the first magnet length 540 is greater than the second magnet length 550. As illustrated in the enhanced view 570 of the first magnet length 540 and the second magnet length 550, the first magnet 525 extends a distance 575 from the second magnet 530. As previously described, in some embodiments, the distance 575 is approximately half the difference between the first magnet length 540 and the second magnet length 550. In other words, in some embodiments, two times the distance 575 is approximately equal to the difference between the first magnet length 540 and the second magnet length 550. In some instances, the first magnet 525 and the second magnet 530 are composed of different magnetic materials. For instance, the first magnet 525 may be a rare earth magnet (or a rare earth material) such as a neodymium magnet or a samarium cobalt magnet, and the second magnet 530 may be a LCF magnet. The magnets 525, 530 may alternatively be composed of aluminum-nickel-cobalt (Alnico), ferrite, or other such magnetic material. It should be understood that any of the magnetic material that comprises the magnets 525, 530 may be changed in alternative embodiments.

[0056] The rotor 520 includes an outer rotor portion 580 and an inner rotor portion 585. The outer rotor portion 580 and the inner rotor portion 585 are connected to one another by a rotor rib 590 that extends from the outer rotor portion 580 to the inner rotor portion 585 in a radial direction away from the center of rotation 560 of the rotor 520. In some examples, the rotor 520 also includes an air slot 595 located between the outer rotor portion 580 and the inner rotor portion 585. The air slot 595 is additionally illustrated in the enhanced view 570. In some instances, the rotor includes more than one air slot 595, or a plurality of air slots. In some examples, each of the first magnet 525 and the second magnet 530 extend into at least one air slot 595.

[0057] FIG. 6 illustrates a memory motor 600, according to some embodiments. The motor 600 includes a stator 605 and a plurality of stator winding slots 610 that receive stator windings. The plurality of stator winding slots 610 are configured to receive a plurality of windings, wound around the stator teeth 615. The motor 600 also includes a rotor 620. The rotor 620 is configured to receive a first magnet 625 and a second magnet 630. In some examples, the first magnet 625 is referred to as an inner magnet, and the second magnet 630 is referred to as anouter magnet. In some instances, the rotor 620 includes a magnet housing portion 633 that separates the first magnet 625 from the second magnet 630. In some examples, the magnet housing portion 633 includes a first thickness 634 and a second thickness 636 that separates the first magnet 625 from the second magnet 630. In some instances, the first thickness 634 and the second thickness 636 are different thicknesses. For example, the first thickness 634 may be greater than the second thickness 636, or vice versa. The first magnet 625 is positioned a first distance 655 from a center of rotation 660 of the rotor 620. The second magnet 630 is positioned a second distance 665 from the center of rotation 660 of the rotor 620. In some examples, the second distance 665 is greater than first distance 655.

[0058] The first magnet 625 includes a first magnet width 635 and a first magnet length 640. In some examples, the first magnet 625 includes a first arm 637, the first arm 637 having a first arm length 639. The first arm 637 extends the first arm length 639 away from the first magnet 625 at approximately a 45 degree angle, and in a radial direction away from the center of rotation 660 of the rotor 620. In some examples, the first arm 637 extends the first arm length 639 away from the first magnet 625 less than a 45 degree angle. For instance, the first arm 637 may extend the first arm length 639 away from the first magnet 625 between a 30 degree angle and a 45 degree angle.

[0059] The second magnet 630 includes a second magnet width 645 and a second magnet length 650. In some examples, the first magnet width 635 is greater than the second magnet width 645. In some examples, the first magnet length 640 is greater than the second magnet length 650. The second magnet 630 includes a second arm 647, the second arm 647 having a second arm length 649. Illustrated in the enhanced view 670 of the motor 600 is the first magnet 625 including the first arm 637 and first arm length 639, and the second magnet 630 including the second arm 647 and second arm length 649. Additionally, the rotor 620 includes an outer rotor portion 680 and an inner rotor portion 685. The outer rotor portion 680 and the inner rotor portion 685 are connected to one another via the magnet housing portion 633, between the first arm 637 and the second arm 647. In some embodiments, the motor 600 generates higher reluctance torque such that less magnetic material can produce the same torque values as a conventional motor.

[0060] FIG. 7 illustrates a memory motor 700, according to some embodiments. The motor 700 includes a stator 705 and a plurality of stator winding slots 710 that receive stator windings. The plurality of stator winding slots 710 are configured to receive a plurality of windings, wound around the stator teeth 715. The motor 700 also includes a rotor 720. The rotor 720 is configured to receive a first magnet 725 and a second magnet 730. In some examples, the first magnet 725 is referred to as an inner magnet, and the second magnet 730 is referred to as an outer magnet. In some instances, the rotor 720 includes a magnet housing portion 733 that separates the first magnet 725 from the second magnet 730. In some examples, the magnet housing portion 733 includes a first thickness 734 and a second thickness 736 that separates the first magnet 725 from the second magnet 730. In some instances, the first thickness 734 and the second thickness 736 are different thicknesses. For example, the first thickness 734 may be greater than the second thickness 736, or vice versa. The first magnet 725 is positioned a first distance 755 from a center of rotation 760 of the rotor 720. The second magnet 730 is positioned a second distance 765 from the center of rotation 760 of the rotor 720. In some examples, the second distance 765 is greater than first distance 755.

[0061] The first magnet 725 includes a first magnet width 735 and a first magnet length 740. In some examples, the first magnet 725 includes a first arm 737, the first arm 737 having a first arm length 739. The first arm 737 extends the first arm length 739 away from the first magnet 725 at approximately a 45 degree angle, and in a radial direction away from the center of rotation 760 of the rotor 720. In some examples, the first arm 737 extends the first arm length 739 away from the first magnet 725 less than a 45 degree angle. For instance, the first arm 737 may extend the first arm length 739 away from the first magnet 725 between a 30 degree angle and a 45 degree angle.

[0062] The second magnet 730 includes a second magnet width 745 and a second magnet length 750. In some examples, the first magnet width 735 is greater than the second magnet width 745. In some examples, the first magnet length 740 is greater than the second magnet length 750. The second magnet 730 includes a second arm 747, the second arm 747 having a second arm length 749. Illustrated in the enhanced view 770 of the motor 700 is the first magnet 725 including the first arm 737 and first arm length 739, and the second magnet 730 including the second arm 747 and second arm length 749. In some instances, the first arm 737 of the first magnet 725 may extend a third arm length 741 away from the first magnet 725, and the secondarm 747 of the second magnet 730 may extend a fourth arm length 743 away from the second magnet 730.

[0063] The third arm length 741 and the fourth arm length 743 are illustrated in the enhanced view 770 of the motor 700. In some instances, the third arm length 741 is approximately half of the first arm length 739 and the fourth arm length 743 is greater than approximately half of the second arm length 749. Additionally, the rotor 720 includes an outer rotor portion 780 and an inner rotor portion 785. The outer rotor portion 780 and the inner rotor portion 785 are connected to one another via the magnet housing portion 733 , between the first arm 737 and the second arm 747. In some embodiments, the motor 700 generates higher reluctance torque such that less magnetic material can produce the same torque values as a conventional motor or motor 600.

[0064] FIG. 8 illustrates a memory motor 800, according to some embodiments. The motor 800 includes a stator 805 and a plurality of stator winding slots 810 that receive stator windings. The plurality of stator winding slots 810 are configured to receive a plurality of windings, wound around the stator teeth 815. The motor 800 also includes a rotor 820. The rotor 820 is configured to receive a first magnet 825 and a second magnet 830. In some examples, the first magnet 825 is referred to as an inner magnet, and the second magnet 830 is referred to as an outer magnet. In some instances, the rotor 820 includes a magnet housing portion 833 that separates the first magnet 825 from the second magnet 830. In some examples, the magnet housing portion 833 includes a first thickness 834 and a second thickness 836 that separates the first magnet 825 from the second magnet 830. In some instances, the first thickness 834 and the second thickness 836 are different thicknesses. For example, the first thickness 834 may be greater than the second thickness 836, or vice versa. The first magnet 825 is positioned a first distance 855 from a center of rotation 860 of the rotor 820. The second magnet 830 is positioned a second distance 865 from the center of rotation 860 of the rotor 820. In some examples, the second distance 865 is greater than first distance 855.

[0065] The first magnet 825 includes a first magnet width 835 and a first magnet length 840. In some examples, the first magnet 825 includes a first arm 837, the first arm 837 having a first arm length 839. The first arm 837 extends the first arm length 839 away from the first magnet 825 at approximately a 45 degree angle, and in a radial direction away from the center of rotation860 of the rotor 820. In some examples, the first arm 837 extends the first arm length 839 away from the first magnet 825 less than a 45 degree angle. For instance, the first arm 837 may extend the first arm length 839 away from the first magnet 825 between a 30 degree angle and a 45 degree angle. The second magnet 830 includes a second magnet width 845 and a second magnet length 850. In some examples, the second magnet 830 includes a second arm 847, the second arm 847 having a second arm length 849. The second arm 847 extends the second arm length 849 away from the second magnet 830 at approximately a 45 degree angle, and in a radial direction away from the center of rotation 860 of the rotor 820. In some examples, the second arm 847 extends the second arm length 849 away from the second magnet 830 less than a 45 degree angle. For instance, the second arm 847 may extend the second arm length 849 away from the second magnet 830 between a 30 degree angle and a 45 degree angle.

[0066] In some instances, the first magnet 825 includes a first magnetic portion 871 and a second magnetic portion 872. In some examples, the first magnet 825 is made of multiple magnetic materials. For instance, the first magnetic portion 871 may be a rare earth magnet such as a neodymium magnet or a samarium cobalt magnet, and a second magnetic portion 872 may be a LCF magnet. In some instances, the second magnet 830 includes a third magnetic portion 873 and a fourth magnetic portion 874. Similar to the first magnet 825, the third magnetic portion 873 and the fourth magnetic portion 874 may be made of multiple magnetic materials. For example, the third magnetic portion 873 may be a rare earth magnet (or a rare earth material) such as a neodymium magnet or a samarium cobalt magnet, and the fourth magnetic portion 874 may be a LCF magnet. In some embodiments, the motor 800 prevents the LCF magnets from being re-magnetized by the rare earth magnets. The motor 800 are well-suited for higher torque applications.

[0067] Additionally, the rotor 820 includes an outer rotor portion 880 and an inner rotor portion 885. The outer rotor portion 880 and the inner rotor portion 885 are connected to one another via the magnet housing portion 833, between the first arm 837 and the second arm 847. In some embodiments, the motor 800 generates higher reluctance torque such that less magnetic material can produce the same torque values as a conventional motor or motor 600.

[0068] FIG. 9 illustrates a memory motor 900, according to some embodiments. The motor 900 includes a stator 905 and a plurality of stator winding slots 910 that receive stator windings.The plurality of stator winding slots 910 are configured to receive a plurality of windings, wound around the stator teeth 915. The motor 900 also includes a rotor 920. The rotor 920 is configured to receive a first magnet 925 and a second magnet 930. In some examples, the first magnet 925 is referred to as an inner magnet, and the second magnet 930 is referred to as an outer magnet. In some instances, the rotor 920 includes a magnet housing portion 933 that separates the first magnet 925 from the second magnet 930. In some examples, the magnet housing portion 933 includes a first thickness 934 and a second thickness 936 that separates the first magnet 925 from the second magnet 930. In some instances, the first thickness 934 and the second thickness 936 are different thicknesses. For example, the first thickness 934 may be greater than the second thickness 936, or vice versa. The first magnet 925 is positioned a first distance 955 from a center of rotation 960 of the rotor 920. The second magnet 930 is positioned a second distance 965 from the center of rotation 960 of the rotor 920. In some examples, the second distance 965 is greater than first distance 955.

[0069] The first magnet 925 includes a first magnet width 935 and a first magnet length 940. In some examples, the first magnet 925 includes a first arm 937, the first arm 937 having a first arm length 939. The first arm 937 extends the first arm length 939 away from the first magnet 925 at approximately a 45 degree angle, and in a radial direction away from the center of rotation 960 of the rotor 920. In some examples, the first arm 937 extends the first arm length 939 away from the first magnet 925 less than a 45 degree angle. For instance, the first arm 937 may extend the first arm length 939 away from the first magnet 925 between a 30 degree angle and a 45 degree angle. The second magnet 930 includes a second magnet width 945 and a second magnet length 950. In some examples, the second magnet 930 includes a second arm 947, the second arm 947 having a second arm length 949. The second arm 947 extends the second arm length 949 away from the second magnet 930 at approximately a 45 degree angle, and in a radial direction away from the center of rotation 960 of the rotor 920. In some examples, the second arm 947 extends the second arm length 949 away from the second magnet 930 less than a 45 degree angle. For instance, the second arm 947 may extend the second arm length 949 away from the second magnet 930 between a 30 degree angle and a 45 degree angle.

[0070] In some instances, the first magnet 925 includes a first magnetic portion 971 and a second magnetic portion 972. In some examples, the first magnet 925 is made of multiple magnetic materials. For instance, the first magnetic portion 971 may be a LCF magnet, and asecond magnetic portion 872 may be a rare earth magnet (or a rare earth material), such as a neodymium magnet or a samarium cobalt magnet. In some instances, the second magnet 930 includes a third magnetic portion 973 and a fourth magnetic portion 974. Similar to the first magnet 925, the third magnetic portion 973 and the fourth magnetic portion 974 may be made of multiple magnetic materials. For example, the third magnetic portion 973 may be a LCF magnet, and the fourth magnetic portion 974 may be a rare earth magnet such as a neodymium magnet or a samarium cobalt magnet. In some embodiments, the motor 900 prevents the LCF magnets from being re-magnetized by the rare earth magnets. The motor 900 is well-suited for higher speed applications. The rotor 920 includes an outer rotor portion 980 and an inner rotor portion 985. The outer rotor portion 980 and the inner rotor portion 985 are connected to one another via the magnet housing portion 933, between the first arm 937 and the second arm 947. In some embodiments, the motor 900 generates higher reluctance torque such that less magnetic material can produce the same torque values as a conventional motor or motor 600.

[0071] FIG. 10 illustrates a memory motor 1000, according to some embodiments. The motor 1000 includes a stator 1005 and a plurality of stator winding slots 1010 that receive stator windings. The plurality of stator winding slots 1010 are configured to receive a plurality of windings, wound around the stator teeth 1015. The motor 1000 also includes a rotor 1020. The rotor includes an outer rotor portion 1021 and an inner rotor portion 1022. The rotor 1020 is configured to receive a first magnet 1025 and a second magnet 1030. In some embodiments, the magnets 1025, 1030 are configured in a spoke configuration. In some examples, the first magnet 1025 is referred to as an outer magnet, and the second magnet 1030 is referred to as an inner magnet. In some examples, the rotor 1020 includes an outer rib 1033 configured to hold the first magnet 1025. In some embodiments, a first air slot 1034 separates the first magnet 1025 from the outer rib 1033.

[0072] The first magnet 1025 includes a first magnet width 1035 and a first magnet length 1040. In some embodiments, the rotor 1020 includes six first magnets 1025. The second magnet 1030 includes a second magnet length 1045. In some embodiments, the rotor 1020 includes six second magnets 1030. The second magnet 1030 also includes an inner radial length 1047 and an outer radial length 1049. The inner radial length 1047 is positioned a first radial distance 1051 away from a center of rotation 1060 of the rotor 1020, and the outer radial length 1049 is positioned a second radial distance 1053 away from the center of rotation 1060 of the rotor 1020.In some instances, a second air slot 1062 is spaced between the second magnet 1030 and the first magnet 1025. In some embodiments, such as the embodiment illustrated in FIG. 10, there are multiple first and second magnets 1025, 1030. In such embodiments, the second air slot 1062 is positioned between multiples of the second magnet 1030. For instance, the second magnet 1030 may be exposed to one second air slot 1062 on one side and another second air slot 1062 on another side, as illustrated in FIG. 10.

[0073] In some instances, the first magnet 1025 and the second magnet 1030 are made of different magnetic materials. For instance, the first magnet 1025 may be a rare earth magnet such as a neodymium magnet or a samarium cobalt magnet, and the second magnet 1030 may be a LCF magnet. In other instances, the first magnet 1025 may be a LCF magnet, and the second magnet 1030 may be a rare earth magnet such as a neodymium magnet or a samarium cobalt magnet. In some embodiments, the motor 1000 is designed to utilize the flux-concentration effect. As a result, higher torques can be produced using less magnetic material.

[0074] FIG. 11 is a graphical representation of efficiency, electrical current, output power, and speed in revolutions per minute (“RPM”) compared to torque outputs of several different motors in the power tool 100, in accordance with some embodiments. In some examples, the motor represented in graph 1100 is the motor of the power tool 100. The graph 1100 includes a representation of the efficiency of several different motors within the power tool 100. A curve 1102 illustrates an efficiency of one type of motor of the power tool 100 (e g., a standard brushless DC motor including inner rare earth permanent magnets). A curve 1104 illustrates an efficiency of a second type of motor of the power tool 100, such as motor 500 including a memory Alnico magnet. A curve 1106 illustrates an efficiency of a third type of motor of the power tool 100, such as motor 500 including a memory ferrite magnet.

[0075] In some embodiments, the curve 1102 is the efficiency of an internal permanent magnet (“IPM”) motor as torque values increase. In some embodiments, the curve 1104 is the efficiency of motor 500 including the memory Alnico magnet as torque values increase. In some embodiments, the efficiency of motor 500 including the memory Alnico magnet diminishes at a faster rate than the IPM motor for high torque values. In some embodiments, the curve 1106 is the efficiency of motor 500 including the memory ferrite magnet as torque values increase. Insome embodiments, the efficiency of the TPM motor diminishes at a faster rate than the motor 500 including the memory ferrite magnet for a high torque values.

[0076] Graph 1100 additionally includes a representation of the electrical current of several different motors within the power tool 100. A curve 1110 illustrates an electrical current of one type of motor of the power tool 100, such as the IPM motor. A curve 1112 illustrates an electrical current of a second type of motor of the power tool 100, such as motor 500 including the memory Alnico magnet. A curve 1114 illustrates an electrical current of a third type of motor of the power tool 100, such as motor 500 including the memory ferrite magnet. In some embodiments, the curve 1110 is the electrical current level of the IPM motor as torque values increase. In some embodiments, the curve 11 12 is the electrical current of motor 500 including the memory Alnico magnet as torque values increase. In some embodiments, as torque increases, the electrical current of both the IPM motor and the motor 500 including the memory Alnico magnet is approximately equal for any given torque value. In some embodiments, the curve 1114 is the electrical current of motor 500 including the memory ferrite magnet as torque values increase. In some embodiments, as torque increases, the electrical current of the IPM motor, the motor 500 including the memory Alnico magnet, and the motor 500 including the memory ferrite magnet are approximately equal to each other until approximately 1.4Nm of torque.

[0077] Graph 1100 additionally includes a representation of the RPM of several different motors within the power tool 100. A curve 1118 illustrates an RPM of one type of motor of the power tool 100, such as the IPM motor. A curve 1120 illustrates an RPM of a second type of motor of the power tool 100, such as the motor 500 including the memory Alnico magnet. A curve 1122 illustrates an RPM of a third type of motor of the power tool 100, such as the motor 500 including the memory ferrite magnet. In some embodiments, the curve 1118 is the RPM level of the IPM motor as torque values increase. In some embodiments, the curve 1120 is the RPM of the motor 500 including the memory Alnico magnet as torque values increase. In some embodiments, as torque increases, the RPM of the motor 500 including the memory Alnico magnet starts at a higher level and then diminishes at a faster rate than the RPM of the IPM motor for a given torque value. In some embodiments, the curve 1122 is the RPM of the motor 500 including the memory ferrite magnet as torque values increase. In some embodiments, as torque increases, the RPM of the motor 500 including the memory ferrite magnet starts at ahigher level and then diminishes at a slower rate than the RPM of the IPM motor for a given torque value. In some embodiments, each motor operates at approximately the same speed at higher torques.

[0078] Graph 1100 additionally includes a representation of the output power, in Watts, of several different motors within the power tool 100. A curve 1128 illustrates an output power of one type of motor of the power tool 100, such as the IPM motor. A curve 1130 illustrates an output power of a second type of motor of the power tool 100, such as the motor 500 including the memory Alnico magnet. A curve 1132 illustrates an output power of a third type of motor of the power tool 100, such as the motor 500 including the memory ferrite magnet. In some embodiments, the curve 1 128 is the output power level of IPM motor as torque values increase. In some embodiments, the curve 1130 is the output power level of the motor 500 including the memory Alnico magnet as torque values increase. In some embodiments, the curve 1132 is the output power level of the motor 500 including the memory ferrite magnet as torque values increase. In some embodiments, each motor operates at approximately the same output power level.

[0079] Additionally, each of the motor configurations described herein may include a low- coercive-force magnet. In some embodiments, any magnet within the motor may be a low- coercive-force magnet. In some embodiments, the LCF magnets are magnetized for torques above approximately 0.2Nm.REPRESENTATIVE FEATURES

[0080] Representative features are set out in the following clauses, which stand alone or may be combined, in any combination, with one or more features disclosed in the text and / or drawings of the specification.Clause 1. A power tool comprising: a housing; and a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings, and a rotor including a first magnet positioned a first distance from a center of rotation of the rotor and a second magnet positioned a second distance from the center of the rotation of the rotor; wherein the first magnet is made of a rare earth material and the second magnet is a low- coercive-force magnet.Clause 2. The power tool of clause 1 , wherein: the rotor further includes an outer rotor portion and an inner rotor portion; and the outer rotor portion and the inner rotor portion are connected to one another by a rotor rib that extends from the outer rotor portion to the inner rotor portion in a radial direction away from the center of rotation of the rotor.Clause 3. The power tool of clause 2, wherein the rotor further includes an air slot located between the outer rotor portion and the inner rotor portion.Clause 4. The power tool of clause 3, wherein the first magnet extends a first distance into the air slot and the second magnet extends a second distance into the air slot.Clause 5. The power tool of clause 1, wherein the rotor further includes a magnet housing portion that separates the first magnet from the second magnet.Clause 6. The power tool of clause 5, wherein the magnet housing portion includes a first thickness and a second thickness, the first thickness being greater than the second thickness.Clause 7. The power tool of clause 1, wherein the first magnet includes a first arm extending a first arm length away from the first magnet at between approximately 30 degrees and approximately 45 degrees.Clause 8. The power tool of clause 7, wherein: the first magnet includes a second arm length extending away from the first magnet; and the second arm length is approximately half the first arm length.Clause 9. The power tool of clause 1, wherein the first magnet includes a first magnet portion and second magnet portion, the first magnet portion including a rare earth material and the second magnet portion including a low-coercive-force magnet.Clause 10. A power tool comprising: a housing; and a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings,and a rotor including: a first magnet including first arm having a first arm length and a first arm width, and a second magnet including second arm having a second arm length and a second arm width, wherein the first arm extends the first arm length away from the first magnet at approximately a 45 degree angle in a radial direction away from a center of rotation of the rotor, wherein the first magnet is made of a rare earth material and the second magnet is a low- coercive-force magnet.Clause 11. The power tool of clause 10, wherein the rotor further includes: an outer rotor portion and an inner rotor portion, and an air slot located between the outer rotor portion and the inner rotor portion, wherein the first magnet extends a first distance into the air slot and the second magnet extends a second distance into the air slot, and wherein the outer rotor portion and the inner rotor portion are connected to one another by a rotor rib that extends from the outer rotor portion to the inner rotor portion in the radial direction away from the center of rotation of the rotor.Clause 12. The power tool of clause 10, wherein the rotor further includes: a magnet housing portion that separates the first magnet from the second magnet, the magnet housing portion including a first thickness and a second thickness, the first thickness being greater than the second thickness.Clause 13. The power tool of clause 10, wherein: the first magnet includes a third arm length extending away from the first magnet; and the third arm length is approximately half the first arm length.Clause 14. The power tool of clause 10, wherein the first magnet includes a first magnet portion and second magnet portion, the first magnet portion including a rare earth material and the second magnet portion including a low-coercive-force magnet.Clause 15. A power tool comprising: a housing; and a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings, and a rotor including: a first air slot, a first magnet configured in a spoke configuration, and asecond magnet including an inner radial length and an outer radial length, wherein the inner radial length is a first radial distance away from a center of rotation of the rotor, and the outer radial length is a second radial distance away from the center of rotation of the rotor, wherein the first magnet is separated from the second magnet by a second air slot, and wherein the first magnet is made of a rare earth material and the second magnet is a low-coercive-force magnet.Clause 16. The power tool of clause 15, wherein the first air slot separates the first magnet from an outer rib of the rotor.Clause 17. The power tool of clause 15, wherein the rotor further includes: a plurality of first magnets and a plurality of second magnets, wherein each of the plurality of second magnets is separated by respective second air slots.Clause 18. The power tool of clause 15, wherein the rotor further includes: an inner rotor portion; an outer rotor portion; and a plurality of second air slots, wherein the second magnet extends a magnet length from the inner rotor portion to the outer rotor portion, and wherein a first portion of the second magnet is exposed to a first of a plurality of second air slots and a second portion of the second magnet is exposed to a second of the plurality of second air slots.Clause 19. The power tool of clause 15, wherein the outer radial length is greater than the inner radial length.Clause 20. The power tool of clause 15, wherein the rotor includes six first magnets configured in the spoke configuration.

[0081] Thus, embodiments described herein provide a power tool including a low-coercive- force magnet. Although the disclosure has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the disclosure as described. Various features and advantages are set forth in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A power tool comprising: a housing; and a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings, and a rotor including a first magnet positioned a first distance from a center of rotation of the rotor and a second magnet positioned a second distance from the center of the rotation of the rotor; wherein the first magnet is made of a rare earth material and the second magnet is a low-coercive-force magnet.

2. The power tool of claim 1, wherein: the rotor further includes an outer rotor portion and an inner rotor portion; and the outer rotor portion and the inner rotor portion are connected to one another by a rotor rib that extends from the outer rotor portion to the inner rotor portion in a radial direction away from the center of rotation of the rotor.

3. The power tool of claim 2, wherein the rotor further includes an air slot located between the outer rotor portion and the inner rotor portion.

4. The power tool of claim 3, wherein the first magnet extends a first distance into the air slot and the second magnet extends a second distance into the air slot.

5. The power tool of claim 1, wherein the rotor further includes a magnet housing portion that separates the first magnet from the second magnet.

6. The power tool of claim 5, wherein the magnet housing portion includes a first thickness and a second thickness, the first thickness being greater than the second thickness.

7. The power tool of claim 1 , wherein the first magnet includes a first arm extending a first arm length away from the first magnet at between approximately 30 degrees and approximately 45 degrees.

8. The power tool of claim 7, wherein: the first magnet includes a second arm length extending away from the first magnet; and the second arm length is approximately half the first arm length.

9. The power tool of claim 1, wherein the first magnet includes a first magnet portion and second magnet portion, the first magnet portion including a rare earth material and the second magnet portion including a low-coercive-force magnet.

10. A power tool compri sing : a housing; and a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings, and a rotor including: a first magnet including first arm having a first arm length and a first arm width, and a second magnet including second arm having a second arm length and a second arm width, wherein the first arm extends the first arm length away from the first magnet at approximately a 45 degree angle in a radial direction away from a center of rotation of the rotor, wherein the first magnet is made of a rare earth material and the second magnet is a low-coercive-force magnet.

11. The power tool of claim 10, wherein the rotor further includes: an outer rotor portion and an inner rotor portion, and an air slot located between the outer rotor portion and the inner rotor portion,wherein the first magnet extends a first distance into the air slot and the second magnet extends a second distance into the air slot, and wherein the outer rotor portion and the inner rotor portion are connected to one another by a rotor rib that extends from the outer rotor portion to the inner rotor portion in the radial direction away from the center of rotation of the rotor.

12. The power tool of claim 10, wherein the rotor further includes: a magnet housing portion that separates the first magnet from the second magnet, the magnet housing portion including a first thickness and a second thickness, the first thickness being greater than the second thickness.

13. The power tool of claim 10, wherein: the first magnet includes a third arm length extending away from the first magnet; and the third arm length is approximately half the first arm length.

14. The power tool of claim 10, wherein the first magnet includes a first magnet portion and second magnet portion, the first magnet portion including a rare earth material and the second magnet portion including a low-coercive-force magnet.

15. A power tool compri sing : a housing; and a motor assembly positioned within the housing, the motor assembly including: a stator with winding slots that receive stator windings, and a rotor including: a first air slot, a first magnet configured in a spoke configuration, and a second magnet including an inner radial length and an outer radial length, wherein the inner radial length is a first radial distance away from a center of rotation of the rotor, and the outer radial length is a second radial distance away from the center of rotation of the rotor,wherein the first magnet is separated from the second magnet by a second air slot, and wherein the first magnet is made of a rare earth material and the second magnet is a low- coercive-force magnet.

16. The power tool of claim 15, wherein the first air slot separates the first magnet from an outer rib of the rotor.

17. The power tool of claim 15, wherein the rotor further includes: a plurality of first magnets and a plurality of second magnets, wherein each of the plurality of second magnets is separated by respective second air slots.

18. The power tool of claim 15, wherein the rotor further includes: an inner rotor portion; an outer rotor portion; and a plurality of second air slots, wherein the second magnet extends a magnet length from the inner rotor portion to the outer rotor portion, and wherein a first portion of the second magnet is exposed to a first of a plurality of second air slots and a second portion of the second magnet is exposed to a second of the plurality of second air slots.

19. The power tool of claim 15, wherein the outer radial length is greater than the inner radial length.

20. The power tool of claim 15, wherein the rotor includes six first magnets configured in the spoke configuration.

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