US20220200368A1 - Brushless dc motor with improved slot fill - Google Patents
Brushless dc motor with improved slot fill Download PDFInfo
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- US20220200368A1 US20220200368A1 US17/550,315 US202117550315A US2022200368A1 US 20220200368 A1 US20220200368 A1 US 20220200368A1 US 202117550315 A US202117550315 A US 202117550315A US 2022200368 A1 US2022200368 A1 US 2022200368A1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
- H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/12—Stationary parts of the magnetic circuit
- H02K1/16—Stator cores with slots for windings
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/12—Stationary parts of the magnetic circuit
- H02K1/16—Stator cores with slots for windings
- H02K1/165—Shape, form or location of the slots
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
- H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
- H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/28—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
- H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
- H02K21/14—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures
- H02K21/16—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures having annular armature cores with salient poles
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K3/00—Details of windings
- H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
- H02K3/28—Layout of windings or of connections between windings
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K3/00—Details of windings
- H02K3/46—Fastening of windings on the stator or rotor structure
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K3/00—Details of windings
- H02K3/46—Fastening of windings on the stator or rotor structure
- H02K3/52—Fastening salient pole windings or connections thereto
- H02K3/521—Fastening salient pole windings or connections thereto applicable to stators only
- H02K3/522—Fastening salient pole windings or connections thereto applicable to stators only for generally annular cores with salient poles
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
- H02K7/145—Hand-held machine tool
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
- H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
- H02K9/06—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium with fans or impellers driven by the machine shaft
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
- B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
- B25F5/001—Gearings, speed selectors, clutches or the like specially adapted for rotary tools
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/12—Stationary parts of the magnetic circuit
- H02K1/14—Stator cores with salient poles
- H02K1/146—Stator cores with salient poles consisting of a generally annular yoke with salient poles
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/20—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for measuring, monitoring, testing, protecting or switching
- H02K11/21—Devices for sensing speed or position, or actuated thereby
- H02K11/215—Magnetic effect devices, e.g. Hall-effect or magneto-resistive elements
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/30—Structural association with control circuits or drive circuits
- H02K11/33—Drive circuits, e.g. power electronics
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K2203/00—Specific aspects not provided for in the other groups of this subclass relating to the windings
- H02K2203/03—Machines characterised by the wiring boards, i.e. printed circuit boards or similar structures for connecting the winding terminations
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
- H02K2213/03—Machines characterised by numerical values, ranges, mathematical expressions or similar information
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Windings For Motors And Generators (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
- Permanent Magnet Type Synchronous Machine (AREA)
Abstract
A brushless direct-current (BLDC) motor for a power tool includes a rotor assembly and a stator assembly including a stator comprising a stator core and stator teeth radially extending from the stator core and defining slots therebetween, and stator windings wound on the stator teeth. The stator has an inner diameter defined by inner ends of the stator teeth and an outer diameter defined by an outer surface of the stator core. A ratio of the inner diameter to the outer diameter is in the range of 0.5 to 0.53. The stator core has a variable thickness and, for each slot, includes a first portion forming an approximately right angle with the respective stator tooth and a second portion that is substantially normal to a radius of the stator assembly and forms an angle of approximately 25 to 35 degrees with the first portion.
Description
- This patent application claims the benefit of U.S. Provisional Application No. 63/129,797 filed Dec. 23, 2020, which incorporated herein by reference in its entirety.
- This disclosure relates to a brushless motor assembly for a rotary tool, and particularly to a brushless motor assembly with high power density.
- According to an embodiment of the invention, a power tool is provided including a housing and a brushless direct-current (BLDC) motor disposed within the housing.
- In an embodiment, the motor includes a rotor assembly including rotor shaft extending along a longitudinal axis and a rotor supporting magnets mounted on the rotor shaft; and a stator assembly including a stator comprising a stator core and stator teeth radially extending from the stator core and defining slots therebetween, and stator windings wound on the stator teeth. In an embodiment, the stator has an inner diameter defined by inner ends of the stator teeth and an outer diameter defined by an outer surface of the stator core, a ratio of the inner diameter to the outer diameter being in the range of 0.5 to 0.53. In an embodiment, the stator core has a variable thickness and, for each slot, includes a first portion forming an approximately right angle with the respective stator tooth and a second portion that is substantially normal to a radius of the stator assembly and forms an angle of approximately 25 to 35 degrees with the first portion.
- In an embodiment, the stator outer diameter is in the range of 50 mm to 70 mm.
- In an embodiment, each slot has an area of greater than or equal to approximately 29 mm{circumflex over ( )}2.
- In an embodiment, the second portion of the stator core has a maximum thickness in alignment with a centerline of the slot that is in the range of approximately 3.6 mm to 3.8 mm.
- In an embodiment, the second portion of the stator core has a minimum thickness proximate the first portion that is in the range of approximately 3 mm to 3.4 mm.
- In an embodiment, each stator tooth has a thickness that is approximately 1.9 to 2.1 times the minimum thickness of the second portion of the stator core.
- In an embodiment, each stator winding comprises at least 19 turns of 18 gauge wire.
- In an embodiment, each stator winding comprises at least 30 turns of 19.5 gauge wire.
- In an embodiment, each stator winding comprises at least 38 turns of 20.5 gauge wire.
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FIG. 1 is a side cross-sectional view of a power tool, according to an embodiment. -
FIG. 2 depicts a perspective view of a motor provided within the power tool, according to an embodiment. -
FIG. 3 depicts a perspective exploded view of the motor including a fan mounted on a rotor shaft adjacent the motor. -
FIGS. 4 and 5 respectively depict a side cross-sectional view and a perspective cross-sectional view of the motor, according to an embodiment. -
FIG. 6 depicts an axial cross-sectional view of stator assembly and rotor assembly of the motor, according to an embodiment. -
FIG. 7 depicts an axial cross-sectional view of the stator assembly and rotor assembly, according to an alternative embodiment. -
FIG. 8 depicts a perspective view of the stator assembly alone without the circuit board, according to an embodiment. -
FIG. 9 depicts a perspective view of the stator assembly with the circuit board mounted thereon, according to an embodiment. -
FIG. 10 depicts a side partially exploded view of the stator assembly and the circuit board, according to an embodiment. -
FIGS. 11A through 11D depict various layers of the multi-layers circuit board, according to an embodiment. -
FIG. 12 depicts a circuit diagram of a parallel-delta configuration between the phases of the motor, according to an embodiment. -
FIG. 13 depicts a partial perspective view of the stator assembly focusing on a single stator terminal disposed between two stator windings, according to an embodiment. -
FIG. 14A depicts a simple circuit diagram of the parallel sets of stator windings, according to an embodiment. -
FIG. 14B depicts a simple winding diagram of the parallel sets of stator windings, according to an embodiment. -
FIGS. 15A and 15B depict partial cross-sectional views of a stator slot in which stator windings are wound using 19 AWG and 21.5 AWG magnet wires respectively, according to an embodiment. -
FIG. 16 depicts a partial axial view of the stator assembly, according to an embodiment. -
FIG. 17 depicts a side view of the stator without the windings, according to an embodiment. -
FIG. 18A depicts a side view of a conventional stator with a stator core having a uniform thickness of approximately 4.8 mm and stator teeth having a thickness of approximately 6.4 mm, according an embodiment. -
FIG. 18B depicts a side view of a stator similar to the stator ofFIG. 18A , having a stator core with a reduced uniform thickness of approximately 3.5 mm andstator teeth 214 having a thickness of approximately 6.4 mm, according to an embodiment. -
FIG. 18C depicts a side view of side view of a stator similar toFIG. 18B , having a stator core with a uniform thickness of approximately 3.5 mm, but with stator teeth having a reduced thickness of approximately 5.9 mm, according to an embodiment. -
FIG. 18D depicts a cross-sectional view of magnet wires having an optimized geometric layout for maximizing wire density of the stator windings, according to an embodiment. -
FIG. 18E depicts a side view of side view of a stator similar toFIG. 18C but including a stator core and stator teeth shaped to improve wire layout as shown inFIG. 18D in order to increase wire density of the stator windings, according to an embodiment. -
FIG. 18F depicts a side view of side view of a stator corresponding toFIGS. 3-17 , according to an embodiment. -
FIG. 19 depicts a comparative diagram showing the maximum power output performing of motor including a conventional stator, an embodiment of an improved stator interfacing a rotor having embedded magnets, and an embodiment of an improved stator interfacing a rotor having surface-mount magnets. -
FIG. 20 depicts the side cross-sectional view ofFIG. 4 , additionally depicting motor magnetic length and electrical length, according to an embodiment. -
FIG. 21 depicts a table summarizing the motor performance characteristics in comparison to examples of comparable conventional motors, according to an embodiment. -
FIG. 22 depicts a perspective view of the motor assembly with the circuit board having an alternative terminal arrangement, according to an embodiment. -
FIG. 23 depicts a perspective view of the motor including the terminal arrangement ofFIG. 22 , according to an embodiment. -
FIG. 24 depicts a perspective view of the motor with a power module mounted directed to the motor housing, according to an embodiment. -
FIG. 25 depicts a partial perspective view of an electric edger including the above-described motor and power module arrangement, according to an embodiment -
FIG. 26 depicts a partial perspective view of the electric edger with a front portion of its housing removed to expose the motor and the power module, according to an embodiment. - The following description illustrates the claimed invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the disclosure, describes several embodiments, adaptations, variations, alternatives, and uses of the disclosure, including what is presently believed to be the best mode of carrying out the claimed invention. Additionally, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
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FIG. 1 is a side cross-sectional view of apower tool 10, according to an embodiment. In an embodiment,power tool 10 is provided including ahousing 12 having agear case 14, amotor case 16, ahandle portion 18, and abattery receiver 20.Power tool 10 as shown herein is an angle grinder with thegear case 14 housing agearset 22 that drives anoutput spindle 24 arranged to be coupled to a grinding, sanding, or cutting disc (not shown, herein referred to as “accessory wheel”). It should be understood, however, that the teachings of this disclosure may apply to any other power tool including, but not limited to, a saw, drill, sander, impact driver, hammer drill, cutting tool, polisher, and the like.Gearset 22 may operate theoutput spindle 24 at a 90-degree angle orientation or in a linear orientation. - In an embodiment, the
motor case 16 attaches to a rear end of thegear case 14 and houses amotor 100 operatively connected to the gear set 22. In an embodiment, themotor 28 is a brushless direct-current (BLDC) motor that rotatably drives arotor shaft 102, which in turn rotatably drives theoutput spindle 24 via thegearset 22. - In an embodiment, the
handle portion 18 extends from a rear end of themotor case 16 and includes atrigger assembly 36 operatively connected to aswitch module 38 disposed within thehandle portion 18, which is in turn coupled to acontrol module 40 disposed close to thebattery receiver 20 for controlling the battery discharge and the operation of themotor 100. Thebattery receiver 20 is provided at a rear end of thehandle portion 18 for detachable engagement with a battery pack (not shown) to provide power to themotor 100. - In an exemplary embodiment, the battery pack may be a 60-volt max lithium-ion type battery pack, although battery packs with other battery chemistries, shapes, voltage levels, etc. may be used in other embodiments. In various embodiments, the
battery receiver 20 and battery pack may be a sliding pack disclosed in U.S. Pat. No. 8,573,324, hereby incorporated by reference. However, any suitable battery receiver and battery back configuration, such as a tower pack or a convertible 20V/60V battery pack as disclosed in U.S. patent application Ser. No. 14/715,258 filed May 18, 2015, also incorporated by reference, can be used. The present embodiment is disclosed as a cordless, battery-powered tool. However, in alternate embodiments power tool can be corded, AC-powered tools. For instance, in place of the battery receiver and battery pack, thepower tool 10 include an AC power cord coupled to a transformer block to condition and transform the AC power for use by the components of the power tools.Power tool 10 may for example include a rectifier circuit adapted to generate a positive current waveform from the AC power line. An example of such a tool and circuit may be found in US Patent Publication No. 2015/0111480, filed Oct. 18, 2013, which is incorporated herein by reference in its entirety. - In an embodiment, the
control module 40 is electronically coupled to apower module 42 provided in this embodiment adjacent themotor 100 to control flow of electric power to themotor 100.Power module 42 may alternatively be provided as a part of the same package as thecontrol module 40 or disposed at a different location of the power tool. In an embodiment, thepower module 42 includes six power switches (e.g., FETs or IGBTs) configured as a three-phase inverter switch. Thecontrol module 40 controls a switching operation of thepower module 42 to regulate a supply of power from the battery pack to themotor 100. Thecontrol module 40 uses the input from theswitch module 38 to set a target speed for themotor 100. When thetrigger assembly 36 is released, in an embodiment, thecontrol module 40 activates the low-side switches or the high-side switches of thepower module 42 simultaneously for regenerative electronic braking of the motor. A description of the power and control modules and electronic braking of the motor can be found in US Patent Publication No. 2017/0234484, filed Feb. 10, 2017, which is incorporated herein by reference in its entirety. -
FIG. 2 depicts a perspective view of themotor 100, according to an embodiment.FIG. 3 depicts a perspective exploded view of themotor 100 including a fan 106 mounted on therotor shaft 102 adjacent themotor 100.FIGS. 4 and 5 respectively depict a side cross-sectional view and a perspective cross-sectional view of themotor 100, according to an embodiment. Themotor 100 is discussed in detail herein with reference to these figures. - In an embodiment,
motor 100 includes a motor housing (or motor can) 110 configured and shaped to house and support themotor 100 components. In an embodiment,motor housing 110 includes a generallycylindrical body 112 that includes an open end for receiving themotor 100 components. On the other end of thebody 112, a series ofradial members 114 are formed.Radial members 114 extend towards from thebody 112 towards acentral bearing pocket 116. In this embodiment,radial members 114 include a series of openings therebetween, thoughradial members 114 may be alternatively with a primarily solid wall. In an embodiment, thebody 112 further includes a series ofair gaps 118 in conjunction with the openings.Air gaps 118 are formed between a series of legs 119 formed at the end of thebody 112 adjoining theradial members 114. - In an embodiment,
motor 100 further includes astator assembly 120 and arotor assembly 140. In an embodiment,stator assembly 120 is disposed outside therotor assembly 140, though many principles of this disclosure may also apply to an outer-rotor motor. In an embodiment,motor 100 further includes acircuit board 150 secured to an end of thestator assembly 120 inside themotor housing 110. These features are described herein in detail. -
FIG. 6 depicts an axial cross-sectional view of thestator assembly 120 androtor assembly 140, according to an embodiment. Referring to this figure, and with continued reference toFIGS. 3 and 4 ,stator assembly 120, in an embodiment, includes astator 122 that is preferably made up of a series of laminations. The outer diameter (OD) of thestator 122 is sized to be fixedly received within thebody 112 of themotor housing 110. Thestator 122 includes a stator core (or back-iron) 124 and a series of inwardly-projectingteeth 126 around which a series ofstator windings 128 are wound. - Specifically,
stator teeth 126 form a series ofslots 127 in between, andstator windings 128 are wound inside theslots 127 around therespective stator teeth 126. The number ofstator teeth 126 andstator windings 128 may corresponding to the number of electronically commutated phases of themotor 100. In an embodiment, wheremotor 100 is a three-phase motor, sixteeth 126 and six sets ofwindings 128 may be provided. - In an embodiment,
rotor assembly 140 includes arotor 142 that is preferably made up on a series of laminations mounted on therotor shaft 102 and disposed within thestator assembly 140. In an embodiment, a series of discretepermanent magnets 144 are embedded within therotor 142 in a N-S-N-S orientation extending along a longitudinal axis of therotor shaft 102. The magnetic interface between themagnets 144 and thestator windings 128, as phases of themotor 100 are sequentially energized, cause rotation of therotor assembly 140 within thestator assembly 120. In an embodiment,rotor 142 includes a series ofhumped surfaces 146 in-line with centers of thepermanent magnets 144 for noise and vibration reduction. - Referring back to
FIGS. 2 and 3 , in an embodiment,air gaps 118 of themotor housing 110, together with thecircuit board 150, form apertures around thestator assembly 120, allowing entry of ambient air into themotor 100 to cool the motor components. In an embodiment,air gaps 118 of themotor housing 110 are substantially aligned with thestator windings 128 and legs 119 of themotor housing 110 are substantially aligned with thestator terminals 170 to cover thestator terminals 170. - Referring back to
FIGS. 4 and 5 , in an embodiment,rear end insulator 130 andfront end insulator 132 are disposed on axial ends of thestator 122 to provide electrical insulation between thestator windings 128 and thestator 122. In an embodiment, the rear andfront end insulators stator 122 when viewed longitudinally and are mounted on the axial ends of thestator 122 prior to the winding process. In an embodiment, as discussed later below,rear end insulator 130 further includes features for supporting a series ofstator terminals 170 in the direction of thecircuit board 150. - In an embodiment, rear and
front rotor bearings rotor shaft 102, in this example on opposite sides of therotor 142, to provide radial and/or axial support for therotor assembly 140 relative to thepower tool 10, themotor housing 110, and/orstator assembly 120. In the illustrated example, therear bearing 147 is received within bearingpocket 116 of themotor housing 110 andfront bearing 148 is supported via a wall or support structure of thetool housing 12. The rear andfront rotor bearings rotor 142 relative to thestator 122 to allow rotation of therotor 142 within thestator 122 while maintaining radial and axial structural support for therotor assembly 140. In an embodiment,central opening 156 of thecircuit board 150 has a greater diameter than the rear rotor bearing 147 so the rear rotor bearing 147 can be passed through thecentral opening 156 and securely received within thebearing pocket 116 during the assembly process. -
FIG. 7 depicts an axial cross-sectional view of thestator assembly 120 androtor assembly 140, according to an alternative embodiment. In this embodiment, apermanent magnet ring 149 is surface mounted on therotor 142.Magnet ring 149 is either includes four magnet segments each extending 90 degrees of angular distance and adjoining at a N-S-N-S orientation. In an embodiment, this orientation reduces magnetic flux leakage and increases the power output density of the motor in comparison to the embedded rotor magnet design ofFIG. 6 . -
FIG. 8 depicts a perspective view of thestator assembly 120 alone without thecircuit board 150, according to an embodiment.FIG. 9 depicts a perspective view of thestator assembly 120 with thecircuit board 150 mounted thereon, according to an embodiment.FIG. 10 depicts a side partially exploded view of thestator assembly 120 and thecircuit board 150, according to an embodiment.Circuit board 150 and its mounting to thestator assembly 120 is described herein in detail with reference these figures and continued reference toFIGS. 3-5 . - In an embodiment, circuit board 150 (herein also referred to as Hall board) is provided inside the
motor housing 110 adjacent the axial end of thestator assembly 120 and sandwiched between thestator 120 and theradial members 114 of themotor housing 110. In an embodiment,circuit board 150 is disc-shaped including acentral opening 156 through which therotor shaft 102 extends for piloting into thecentral bearing pocket 116 of themotor housing 110. - In an embodiment,
circuit board 150 includes one or more magnetic (Hall)sensors 151 that interact with therotor assembly 140. Signals from theHall sensors 151 are used to detect the angular position of therotor assembly 140. In an embodiment,Hall sensors 151 are positioned in sufficiently close proximity to the rotor magnets to directly sense the angular position of therotor 142 by sensing the magnetic flux of the rotor magnets. Alternatively, in an embodiment, an additional sense magnet ring (not shown) may be disposed on therotor shaft 102 adjacent herotor 102 in close proximity to theHall sensors 151. Additionally, in an embodiment,circuit board 150 includes conductive traces to connect thestator windings 128 in a series and/or parallel and delta and/or wye configuration. - In an embodiment,
circuit board 150 includes a series ofopenings 164 arranged close to the outer circumference arranged to receive ends ofstator terminals 170.Stator terminals 170, as described later in detail, are mounted on therear end insulator 130 of thestator assembly 120 between therespective stator windings 128 and connect to a front surface of the circuit board 150 (facing the stator assembly 120) to electrically connect thestator windings 128 to the conductive traces of thecircuit board 150. In an embodiment,openings 164 are conductive vias to facilitate electrical connection between thestator terminals 170 and the metal traces and routings. - In an embodiment,
circuit board 150 further includes acontrol terminal block 152 that includes a ribbon connector for communicating with thecontrol module 40. Thecontrol terminal block 152 includes at least three signals from theHall sensors 151. Thecircuit board 15 further includes apower terminal block 154 for providing power from thepower module 42 to thestator windings 128. In an embodiment, controlterminal block 152 andpower terminal block 154 are mounted on a rear surface of the circuit board 150 (facing away from the stator assembly 120) on opposite sides of thecentral opening 156. - In an embodiment, as best shown in
FIG. 9 ,power terminal block 154 includes a set of conductive terminals 158 (in this case three terminals corresponding to the three phases of the motor 100), each extending perpendicularly from the rear surface of thecircuit board 150 and including an upper opening for soldering or weldment to a power wire (not shown). Thepower terminal block 154 further includes an insulatingmount 160 that is mounted on the rear surface of thecircuit board 150 and includes slots through which theconductive terminals 158 extend from thecircuit board 150. The insulatingmount 160 provides structural and insulative support for theconductive terminals 158, preventing them from being inadvertently bent and encounter one another. In an embodiment, the insulatingmount 160 includes one ormore walls 162 positioned between the adjacentconductive terminals 158 to ensure that contamination of thepower terminal block 154 by metallic particulate does not create electrical shortage between theconductive terminals 158. - In an embodiment,
rear end insulator 130 of thestator assembly 120 includes a series ofaxial support members 134 provided to support thestator terminals 170 in the axial direction of themotor 100. Eachaxial support member 134 includes two posts that form an opening in between for securely receiving and supporting one of thestator terminals 170. In an embodiment, sixaxial support members 134 support sixstator terminals 170 between the respective sets ofstator windings 128. - In an embodiment, two or more (in this example, three) of the
axial support members 134 include threadedopenings 136. Thecircuit board 150 is secured to thestator assembly 120 via a series offasteners 166 received through corresponding openings of thecircuit board 150 into the threadedopenings 136 of therear end insulator 130. - In an embodiment, referring to
FIG. 5 ,axial support members 134 are sized to maintain a minimum distance A between thestator windings 128 and thecircuit board 150, while ensuring that theHall sensors 151 are maintained at a maximum distance B from the rotorpermanent magnets 144 for direct-sensing of thepermanent magnets 144, where A>=B. In an embodiment, distances A and B both fall in the range of 1 to 6 mm. - In an embodiment, referring to
FIGS. 2 and 3 ,radial members 114 of themotor housing 110 are disposed in contact with the rear surface of thecircuit board 150, with control and power terminals blocks 152 and 154 being received through the openings between theradial members 114 to be accessible for coupling with electrical connectors and wires outside themotor housing 110. In an embodiment, routing thestator windings 128 on thesame circuit board 150 as theHall sensors 156, and placement of thecircuit board 150 inside themotor housing 100, significantly reduces the overall size of themotor 100 assembly, thus increasing the power output density of themotor 100. - In an embodiment, as stated above, control and power terminal blocks 152 and 154 of the
circuit board 150 are received betweenradial members 114 ofmotor housing 110 to facilitate coupling with control and power cords received from the control andpower modules power tool 10. As such, in an embodiment, as best seen inFIG. 4 , at least one radial plane exists that intersects therear bearing 147 of therotor shaft 102, theradial members 114 ofmotor housing 110, and control and power terminals blocks 152 and 154 of thecircuit board 150. - In an embodiment, as stated above,
circuit board 150 includes conductive traces to connect thestator windings 128 in a series and/or parallel and delta and/or wye configuration. In order to maximize the surface areas of the conductive traces in thecircuit board 150, according to an embodiment,circuit board 150 is multi-layered printed circuit board, as described here with reference toFIGS. 11A through 11D . -
FIGS. 11A through 11D depict various layers of themulti-layers circuit board 150, according to an embodiment. In an embodiment, as shown inFIG. 11A ,Hall sensors 151 are mounted on a front surface of thecircuit board 150. In an embodiment, as shown inFIGS. 11B-11D , conductive trace 153 (electrically connecting U and U′ terminals), conductive trace 155 (electrically connecting V and V′ terminals), and conductive trace 157 (electrically connecting W and W′ terminals), are disposed on various inner layers of thecircuit board 150. In an embodiment, each of theconductive routings circuit board 150, thus reducing heat and resistance associated with the conductive traces. - In an embodiment,
conductive traces conductive terminals 158. As shown in the circuit diagram ofFIG. 12 , this arrangement facilitates a parallel between the windings of the same phase and a delta connection between pairs of windings of different phases, according to an embodiment. -
FIG. 13 depicts a partial perspective view of thestator assembly 120 focusing on asingle stator terminal 170 disposed between twostator windings 128. As shown here, and with continued reference toFIGS. 8-10 ,stator terminal 170 includes amain portion 172 received between the posts of theaxial support member 134 normal to the longitudinal axis of themotor 100.Main portion 172 may be planar or include one or more arcuate segments having a similar curvature as thestator 122. A first end of the main portion 172 (away from the circuit board 150) includes atang portion 174 that is folded over the outer surface of themain portion 172. One or morecross-over wire portions 180 connecting theadjacent stator windings 128 located on two sides of thestator terminal 170 are passed through the gap between thetang portion 174 and themain portion 172 before thetang portion 174 is pressed against themain portion 172. A second end of the main portion 172 (closer to the circuit board 150) includes apin 176 that is received within the correspondingperipheral opening 164 of thecircuit board 150. - In an embodiment, start and finish ends of each of the
stator windings 128 are electrically coupled to its twoadjacent stator terminal 170, and as discussed below in detail, connections between opposingstator windings 128 of the same phase in a series of parallel connection, as well as connections betweenstator windings 128 of different phases in a wye or delta configuration, are facilitated via metal routings and/or traces on thecircuit board 150. This arrangement eliminates the need for excessive routing ofcross-over wire portions 180 that connect thestator windings 128 on thestator assembly 120. - In an embodiment, all
stator windings 128 andcross-over wire portions 180 may be wound on thestator 122 using a single continuous magnet wire. The single continuous magnet wire is wound fully for a designated number of turns on onestator tooth 126, passed through thetang portion 174 of anadjacent stator terminal 170, wound fully on theadjacent stator tooth 126 for the designated number of turns, passed through asubsequent tang portion 174, and this process is continued until allstator windings 128 are fully wound with the designated number of turns. The two ends of the magnet wire may be wrapped around thetang portion 174 of thesame stator terminal 170. - In an embodiment, using a smaller diameter magnet wire increases the overall slot fill and wire density within each slot. For example, winding the stator slots fully using a 19 AWG (American Wire Gauge) magnet wire (i.e., a 0.91 mm conductor diameter) may yield only a 51.14% slot fill per unit of area, because the large diameter of the magnet wire results in a less efficient overlay of the wires and larger airgaps between the wires. By contrast, winding the stator slots fully using a 21.5 AWG magnet wire (i.e., a 0.68 mm conductor diameter) yields a 58.61% slot fill. Similarly, winding the stator slots using a 23 AWG magnet wire (i.e., a 0.57 mm conductor diameter) yields a 62.98% slot fill. Increasing slot fill and wire density results in a reduction in the electrical resistance of the motor.
- It is well understood that the number of turns of
stator windings 128 on eachtooth 126 is correlated to the desired torque output of the motor. The more number of turns of the stator windings, the higher the torque output of the motor. According, in order to increase slot fill and reduce electrical resistance of the motor while maintaining the desired number of turns of thestator windings 128 on eachtooth 126, in an embodiment of the invention, two or more sets of stator windings having relatively smaller diameters are provided on each tooth and wound in parallel, as described herein in detail. - In an embodiment, as best seen in
FIG. 13 , two or more sets ofstator windings stator tooth 126, with two or morecross-over wire portions 180 passes between theadjacent stator windings 128 a andadjacent stator windings 128 b. In an embodiment, a first layer ofstator windings 128 a is initially wound on allstator teeth 126 as described above, and a second layer ofstator windings 128 b is wound on thesame stator teeth 126 and in the same sequence on top ofstator windings 128 a to create a parallel connection between therespective stator windings stator tooth 126. This may be accomplished using two separate continuous magnet wires, where a first magnet wire is wound on allstator teeth 126 as described above in a first step to providestator windings 128 a, and a second magnet wire is wound on top of the first magnet wire on allstator teeth 126 in a second step to providestator windings 128 b. Alternatively, the first and second sets ofstator windings -
FIG. 14A depicts a simple circuit diagram of the parallel sets ofstator windings FIG. 14B depicts a simple winding diagram of the parallel sets ofstator windings - This arrangement increases slot fill and reduce electrical resistance of a motor for a given desired number of turns of the stator windings as required by the rated torque output of the motor. For example, in a motor where 19 number of turns of the stator windings is required to achieve a desired torque rating, two sets of
stator windings stator tooth 126 as described above, each at 19 number of turns and using a 21.5 AWG magnet wires. The parallel configuration of the 21.5AWG stator windings stator tooth 126 provides equivalent torque rating as a single set of stator windings using a 19 AWG magnet wire at 19 number of turns, but with a higher slot density and thus reduced electrical resistance. -
FIGS. 15A and 15B depict partial cross-sectional views of astator slot 127 in whichstator windings 128 are wound using 19 AWG and 21.5 AWG magnet wires respectively, according to an embodiment. Since cross-sectional area of a 19 AWG magnet wire is twice the cross-sectional area of 21.5 AWG magnet wire, as shown in these figures, 38 total turns of the 21.5 AWG magnet wires (wound as two sets of 19 turns in parallel) occupies substantially the same cross-sectional area of thestator slots 127 as does 19 turns of a 19 AWG magnet wire. Accordingly, the same torque rating is achieved, even though the parallel arrangement of the stator windings using two 21.5 AWG magnet wires increases slot fill by approximately 15%. Further, the parallel arrangement of the stator windings using two 21.5 AWG magnet wires reduces motor resistance by approximately 10%, improves power output by approximately 5%, and improves thermal efficiency of the motor by approximately 10%, as compared to a single set of 19 AWG magnet wire. - Similarly, in an embodiment, three sets of stator windings may be wound in parallel using 23 AWG magnet wires to further improve slot fill, reduce motor resistance, improve power output, and improve thermal efficiency of the motor. Table 1 below summarizes these findings.
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TABLE 1 Coil Per Tooth Wire Gauge Wire Size Resistance Slot Fill 1 19 AWG 0.91 mm 10.22 mOhms 51.14% 2 21.5 AWG 0.68 mm 9.18 mOhms 58.61% 3 23 AWG 0.57 mm 8.707 mOhms 62.98% - In an embodiment, the diameter of the magnet wire used for the first set of
stator windings 128 a may be different from the diameter of the magnet wire used for the second set of stator windings. 128 b. While this process may complicate the manufacturing process and require use of two winding machines for the same motor, it can provide an optimal slot fill. In yet another embodiment, the number of turns of the first set ofstator windings 128 a may be different from the number of turns of the second set ofstator windings 128 b. -
FIG. 16 depicts a partial axial view of thestator assembly 120, according to an embodiment. As discussed above,cross-over wires 180 are only provided betweenadjacent stator windings 128, and not around thestator 120 between opposite windings of the same phase or windings of different phase. This provides an advantage in that the entire body of thestator terminals 170 can be contained within a firstcircular envelope 190 defined by the outer surface of thestator 120. In an embodiment, the outermost parts of thestator terminals 170 form a secondcircular envelope 192 that has a smaller diameter of the firstcircular envelope 190 defined by the outer surface of thestator 120. This is in contrast to prior art stator designs with in-line stator terminals, where, in order to accommodate a large number of cross-over wires on the end surface of the stator, the stator terminals are mounted on the outer edge of the stator and at least a portion of thestator terminal 170 project outwardly beyond the circumferential envelope defined by the outer surface of thestator 120. -
FIG. 17 depicts a side view of thestator 120 without thewindings 128. Sincecross-over wires 180 do not extend around thestator 120, the thickness of thestator core 124 may be reduced in comparison to conventional stators where cross-over wires are supported on the stator between opposite windings of the same phase or stator windings of different phases. In an embodiment, the thickness of thestator core 124 is approximately in the range of 3.6 to 3.8 mm, preferably approximately 3.7 mm, at its thickest points C at or near the center of the stator slots, and is approximately in the range of 3.0 to 3.4 mm, preferably approximately 3.1 to 3.2 mm, at its thinnest points D proximate thestator teeth 126. This allows the lengths of thestator teeth 126 be similarly reduced and the inner diameter (ID) of thestator 120 to be increased without sacrificing the area of the slots available for disposition ofstator windings 128. In an embodiment, the ratio of the stator inner diameter (ID) to its outer diameter (OD) is in the range of approximately 0.5 to 0.53, preferably approximately 0.51 to 0.52. In an example, where the stator OD is 0.51 mm, the ID may be sized at 26 mm, allowing it to receive a rotor having an outer diameter of 25 mm. - In an embodiment, in order to maximize the area of the slots available for disposition of
stator windings 128, the thickness E of the stator tooth is reduced to approximately 2 times, and in particularly to 1.9 to 2.1 times, the thickness D of thestator core 124. Further, as shown inFIGS. 18A to 18F below, thestator core 124 is shaped to improve the wiring layout and maximize the density of wire per volume within the slots. It is noted that in these figures, a 51 mm diameter stator is depicted by way of example. -
FIG. 18A depicts a side view of aconventional stator 200 with astator core 202 having a uniform thickness of approximately 4.8 mm andstator teeth 204 having a thickness of approximately 6.4 mm, according an embodiment. In this example, the stator ID is 24.5 mm. This arrangement provides a slot area of approximately 20.5 mm2 for disposition of stator windings. In an example, this stator may be wound with up to 21 turns of 20.5 AWG magnet wire. -
FIG. 18B depicts a side view of astator 210 similar tostator 200 ofFIG. 18A , having astator core 212 with a reduced uniform thickness of approximately 3.5 mm andstator teeth 214 having a thickness of approximately 6.4 mm, according to an embodiment. In this example, by merely reducing the thickness of thestator core 212, the slot area is increased to approximately 28 mm2. In an example, this stator may be wound with up to 33 turns of 20.5 AWG magnet wire. -
FIG. 18C depicts a side view of side view of astator 220 similar toFIG. 18B , having astator core 222 with a uniform thickness of approximately 3.5 mm, but withstator teeth 224 having a reduced thickness of approximately 5.9 mm, according to an embodiment. In this example, by reducing the thickness of thestator teeth 224, the slot area is increased to approximately 29 mm2. In an example, this stator may be wound with up to 33 turns of 20.5 AWG magnet wire. -
FIG. 18D depicts a cross-sectional view ofmagnet wires 205 having an optimized geometric layout for maximizing wire density of thestator windings 128, according to an embodiment. In an embodiment of the invention, given the same motor speed and/or torque requirements, the same stator ID and OD, and the same winding machine and process, this layout reduces the amount of air gap between themagnet wires 205. As such, this wiring layout allows a greater number of turns of the magnet wire, or a greater thickness of the magnet wire, to be wound for each stator winding.FIGS. 18E and 18F described below aim to shape the stator core and/or winding to achieve this wire layout. -
FIG. 18E depicts a side view of side view of astator 230 similar toFIG. 18C but including astator core 232 andstator teeth 234 shaped to improve wire layout as shown inFIG. 18D in order to increase wire density of thestator windings 128. In an embodiment,stator 230 includes astator core 232 with a non-uniform thickness of approximately 3.1 mm to 3.8 mm andstator teeth 224 having a non-uniform thickness of approximately 4.9 mm to 8.2 mm, according to an embodiment. In an embodiment,portion 236 of thestator core 232 andportion 238 of thestator teeth 234 are angled to achieve the wire layout as shown inFIG. 18D . While this design in fact reduces the slot area to approximately 26 mm2, it allows thestator 230 to be wound with up to 37 turns of 20.5 AWG magnet wire. -
FIG. 18F depicts a side view of side view of thestator 122, as described inFIGS. 6 and 7 of this disclosure, according to an embodiment.Stator 122 is similar tostator 210 ofFIG. 18E in some respects, but thestator core 124 andstator teeth 126 are shaped to further increase the slot area while optimizing wire layout. In an embodiment,stator core 124 is provided with a non-uniform thickness of approximately 3.1 mm to 3.7 mm (i.e., distances C and D inFIG. 17 ), and eachstator tooth 126 includes a substantially uniform thickness of approximately 35.9 mm (not including the tooth tips), according to an embodiment. In an embodiment, anangular portion 246 of thestator core 124 extends at an angle θ1 from the maininner surface 248 of thestator core 124, where θ1 is approximately in the range of 25 to 35 degrees, preferably approximately 30 degrees.Angular portion 246 forms an angle θ2 with thestator tooth 126 that is approximately in the range of 80 to 100 degrees, preferably approximately 90 degrees. This design substantially achieves the desired wire layout ofFIG. 18D but increases the slot area to approximately 29 mm2. This arrangement allows thestator 122 to be wound with up to 38 turns of 20.5 AWG magnet wire. - The results discussed above are summarized in Table 2 below:
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TABLE 2 Stator 200Stator 210Stator 220Stator 230Stator 122Tooth Width 6.6 mm 6.6 mm 5.9 mm 4.9-8.2 mm 5.9 mm Core Width 4.8 mm 3.5 mm 3.4 mm 3.1-3.8 mm 3.1-3.7 mm ID 24.5 mm 24.5 mm 26 mm 26 mm 26 mm Slot Area 20.5 mm2 27.9 mm2 28.9 mm2 25.7 mm2 29.0 mm2 - The maximum number of turns of different sized magnet wires for each of the stators described above are summarized in Table 3 below:
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TABLE 3 Wire Size Stator 200 Stator 210Stator 220Stator 230Stator 12218.0 AWG 10 T 14 T (+40%) 16 T (+60%) 17 T (+70%) 19 T (+90%) 19.5 AWG 17 T 22 T (+29%) 25 T (+47%) 27 T (+59%) 30 T (+76%) 20.5 AWG 21 T 29 T (+38%) 33 T (+57%) 37 T (+76%) 38 T (+81%) -
FIG. 19 depicts a comparative diagram showing the maximum power output performing of motor including a conventional stator (plot 250),stator 122 interfacing a rotor having embedded magnets (plot 252), andstator 122 interfacing a rotor having surface-mount magnets (plot 254). In this diagram, as is commonly understood by those skilled in the art, the motor power output increases as the motor stack length is increased. In an embodiment, as shown in this diagram, the motor maximum power output of at least 2000 watts may be achieved using a stator having a 35 mm length and 51 mm outer diameter. This represents an improvement of approximately 25% for larger stack length and up to approximately 85% for a smaller stack length. When using the same stator with a surface-mount rotor design, the motor maximum power output of at least 2200 watts may be achieved. This represents an improvement of approximately 35% for larger stack length and up to approximately 125% for a smaller stack length. -
FIG. 20 depicts the side cross-sectional view of themotor 100 similar toFIG. 4 , additionally denoting an electrical envelope and a magnetic envelope of themotor 100, according to an embodiment. - In an embodiment, electrical envelope in this figure designates the total volume of the
motor 100 where electrical and electro-magnetic components, including thecircuit board 150 and all the wiring connections between thestator windings 128, are located. The electrical envelope is the volume of the motor that is peripherally bound by a generallycylindrical boundary 302 extending along a radially outermost portion of thestator assembly 120 and having a diameter OD. The electrical envelope is further axially bound by afront plane 304 at a frontmost point of the stator assembly and the rotor, in this example the frontmost tip of thestator windings 128, and arear plane 306 at a rearmost point of the electro-magnetic part ofcircuit board 150, in this example the surface of thecircuit board 150 opposite thestator assembly 120. Electrical envelope has a length EL. - In an embodiment, the magnetic envelope is bound the generally
cylindrical boundary 302, thefront plane 304, arear plane 308 at a rearmost point of thestator windings 128. The magnetic envelope has a length ML that is smaller than the length EL. -
FIG. 21 depicts a table comparing performance characteristics of themotor 100 to conventional BLDC motors. As demonstrated in this table,motor 100 is capable of producing higher maximum power output and higher motor constant for the given motor electrical envelope 300 than comparable known BLDC motors. - Four examples of
motor 100 are provided in this table including different numbers of parallel sets of stator windings per tooth. The motor electrical envelope for theseexemplary motors 100 are of the same geometry (including stator diameter of 51 mm and electrical length LE of 40 mm) and same volume (approximately 81,670 mm{circumflex over ( )}3 in this example). The motor magnetic envelope for theseexemplary motors 100 are also of the same geometry (including stator diameter of 51 mm and magnetic length ML of 36.4 mm) and same volume (approximately 74,400 mm{circumflex over ( )}3 in this example). By comparison, three exemplary conventional motors are also included. The comparative conventional BLDC motors have the same diameter (example 1), smaller diameter (example 2), and larger diameter (example 3), but the lengths of the respective motors are modified to maintain the same electric envelope (approximately 81,670 mm{circumflex over ( )}3) and magnetic envelope (approximately 74,400 mm{circumflex over ( )}3) as the fourexemplary motors 100. - As can be seen, given the same motor electrical envelope and magnetic envelope described above, the motor maximum power output for
motor 100 increases from 1840 watts to 1895 watts (a 3% increase) when using two parallel windings per tooth, to 1922 watts (a 4% increase) when using three parallel windings per tooth, and to 1950 watts (a 6% increase) when using four parallel windings per tooth. Any of these configurations represents significant increases of maximum power output over conventional BLDC motors of the same size. It can be seen that the conventional BLDC motors having equivalent motor envelope and electrical envelope tomotor 100 produce maximum power output in the range of approximately 1000 watts to 1500 watts, i.e., approximately 18% to 45% less thanmotor 100 given the same size electrical envelope and same size magnetic envelope. - Furthermore, the motor size (Km) constant of
motor 100 increases from when using two or more sets of parallel windings per tooth. As understood by those skilled in the art, the Km constant is a parameter for determining the efficiency and capacity of a motor. The Km constant is calculated as a function of the torque constant Kt and the resistance of the motor R, Km=Kt/R2 or Km=Kt*I/P, where torque constant Kt is the torque produced divided by motor current. Thus, the Km constant represents the capability of the motor to produce power normalized by resistance of the motor. In an embodiment, the Km constant ofmotor 100 increases from 0.0762 N·m/√W to 0.0804 N·m/√W (a 5% increase) when using two parallel windings per tooth, to 0.0826 N·m/√W (an 8% increase) when using three parallel windings per tooth, and to 0.0851 N·m/√W (a 10% increase) when using four parallel windings per tooth. - Any of these configurations represents a significant increase the Km constant over conventional BLDC motors having equivalent motor envelope and electrical envelope to
motor 100. It can be seen that the Km constants of the conventional BLDC motors having equivalent motor envelope and electrical envelope tomotor 100 are in the range of approximately 0.0471 to 0.0636 N·m/√W, i.e., approximately 18% to 50% less than themotor 100 given the same size electrical envelope and same size magnetic envelope. - In an embodiment, to evaluate the motor performance irrespective of the size of the motor, a ratio of the Km constant to the electrical envelope and/or the magnetic envelope is provided.
- In an embodiment, the ratio of the Km constant to the electrical envelope of the motor is greater than 900 (N·m/√W)/m{circumflex over ( )}3 in an embodiment, particularly greater than 940 (N·m/√W)/m{circumflex over ( )}3 in an embodiment, more particularly greater than 980 (N·m/√W)/m{circumflex over ( )}3, and even more particularly greater than 1020 (N·m/√W)/m{circumflex over ( )}3. When using two or more sets of parallel coils per tooth, the ratio of the Km constant to electrical envelope of the motor is greater than 1080 (N·m/√W)/m{circumflex over ( )}3 when using two parallel coils per tooth, greater than 1100 (N·m/√W)/m{circumflex over ( )}3 when using three parallel coils per tooth, and greater than 1140 (N·m/√W)/m{circumflex over ( )}3 when using four parallel coils per tooth. By comparison, the ratios of the Km constant to electrical envelope of conventional BLDC motors are at most 855 (N·m/√W)/m{circumflex over ( )}3. This represents a performance increase, even when using merely a single set of coils per tooth on
motor 100. - In an embodiment, the ratio of the Km constant to the magnetic envelope of the motor is greater than 810 (N·m/√W)/m{circumflex over ( )}3 in an embodiment, particularly greater than 850 (N·m/√W)/m{circumflex over ( )}3 in an embodiment, and more particularly greater than 890 (N·m/√W)/m{circumflex over ( )}3, and even more particularly greater than 930 (N·m/√W)/m{circumflex over ( )}3. When using two or more sets of parallel coils per tooth, the ratio of the Km constant to electrical envelope of the motor is greater than 970 (N·m/√W)/m{circumflex over ( )}3 when using two parallel coils per tooth, greater than 1000 (N·m/√W)/m{circumflex over ( )}3 when using three parallel coils per tooth, and greater than 1030 (N·m/√W)/m{circumflex over ( )}3 when using four parallel coils per tooth. By comparison, the ratios of the Km constant to electrical envelope of conventional BLDC motors are at most 780 (N·m/√W)/m{circumflex over ( )}3. This represents a performance increase, even when using merely a single set of coils per tooth on
motor 100. -
FIG. 22 depicts a perspective view of themotor assembly 120 with thecircuit board 150 mounted thereon, according to an embodiment. In this embodiment, instead of apower terminal block 154 as previously described, thecircuit board 150 is provided with a series of (in this example three) discrete in-line motor terminals 402. In an embodiment, themotor terminals 402 are provided at an equidistant angular orientation, e.g., at 120 degrees apart. In an embodiment, eachmotor terminal 402 is radially in line with one of thestator terminals 170. In an embodiment, eachmotor terminal 402 is mounted on thecircuit board 150 via an insulatingpad 404. In an embodiment, eachmotor terminal 402 includes a slanted portion, allowing an axis of the outer tip of themotor terminal 402 to be positioned close to the outer periphery of thecircuit board 150. -
FIG. 23 depicts a perspective view of themotor 100 including the above-describedmotor terminal 402 arrangement, according to an embodiment.FIG. 24 depicts a perspective view of themotor 100 withpower module 42 mounted directed to themotor housing 110, according to an embodiment. In an embodiment, as previously described,power module 42 includes six power switches (e.g., FETs or IGBTs) configured as a three-phase inverter switch for driving themotor 100. In an embodiment,power module 42 is disc-shaped with a circumference that is approximately equal to or slightly smaller than the circumference of themotor housing 110. In an embodiment,power module 42 includes apower circuit board 420 on which the power switches (not shown) are mounted, and anovermold structure 422 formed around the power switches. In an embodiment,power terminals 426 are further supported by theovermold structure 422 and are coupled to thebattery receptacle 20 and/or theswitch module 38 to supply electric power to the power switches. - In an embodiment,
motor housing 110 is provided with a series ofsupport posts 410 positioned to structurally support thepower module 42. In an embodiment, thepower module 42 is mounted above the support posts 410 and secured to theposts 410 viafasteners 424. In an embodiment, eachsupport post 410 includes twolegs 412 that project around thepower module 42. - In an embodiment, end tips of the
terminals 402 are received into corresponding slots of thepower circuit board 420. This allows thepower circuit board 420 to make a direct electrical connection to theterminals 402, and thus thestator windings 128, without a need for intermediary wires. Accordingly, this embodiments provides a two circuit board arrangement disposed in parallel rearward of thestator assembly 120, withcircuit board 150 being located inside themotor housing 110 and configured to supportHall sensors 151 and metal traces for interconnection of thestator windings 128, andpower circuit board 420 being located outside themotor housing 110 and configured to support the power switches for driving thestator windings 128. - The above-described configuration of the
motor 100, particularly in combination with thepower module 42 mounted directly to the rear of themotor housing 110, provides high power in a small package highly desirable for many power tool, industrial tools, motorized outdoor products, and home appliances.FIG. 1 described above provides an example of a power tool that benefits from the high density advantages of themotor 100 andpower module 42. An example of an outdoor product, in this example an edger, utilizing themotor 100 andpower module 42 of this disclosure, is described here with reference toFIGS. 25 and 26 . -
FIG. 25 depicts a partial perspective view of anelectric edger 500, according to an embodiment. In an embodiment,edger 500 includes a housing 502, ablade guard 504 mounted on one side of the housing 502, alower handle portion 506 extending upwardly from the housing 502 at an angle, atubular rod 508 extending from thelower handle portion 506 to a grip handle (not shown) accommodating a trigger switch (not shown) actuatable by a user, andwheels 510. A battery pack (not shown) may be mounted to theelectric edger 500 near the grip handle to supply electric power. Operational and structural details of theedger 500 are beyond the scope of this disclosure. Reference is made to U.S. Pat. No. 5,325,928, which is incorporated herein by reference in its entirety, for details of an electric edger. -
FIG. 26 depicts a perspective view of theelectric edger 100 with a front portion of the housing 502 removed, according to an embodiment. As shown here, the housing 502 is sized to house themotor 100 and thepower module 42 mounted to the rear of themotor housing 110. An output of themotor 100, which is not visible in this figure, is rotationally coupled, via a gear reduction mechanism and an output spindle, to a cutting blade located within theblade guard 504. As such, in an embodiment, thepower module 42 and themotor housing 110 are compactly contained within the housing 502. In an embodiment, a microcontroller for controlling the switching operation of the power switches is also disposed within the housing 502. In an embodiment, the microcontroller may be provided separately from thepower module 42 or integrally on the circuit board as the power switching within thepower module 42. As such, the housing 502 accommodates all the electronics and control features required for driving the motor. - Example embodiments have been provided so that this disclosure will be thorough, and to fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
- The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
- When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
- Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
- Terms of degree such as “generally,” “substantially,” “approximately,” and “about” may be used herein when describing the relative positions, sizes, dimensions, or values of various elements, components, regions, layers and/or sections. These terms mean that such relative positions, sizes, dimensions, or values are within the defined range or comparison (e.g., equal or close to equal) with sufficient precision as would be understood by one of ordinary skill in the art in the context of the various elements, components, regions, layers and/or sections being described.
- The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
Claims (18)
1. A brushless direct-current (BLDC) motor comprising:
a rotor assembly including rotor shaft extending along a longitudinal axis and a rotor supporting a plurality of magnets mounted on the rotor shaft; and
a stator assembly including a stator comprising a stator core and a plurality of stator teeth radially extending from the stator core and defining a plurality of slots therebetween, and a plurality of stator windings wound on the plurality of stator teeth,
wherein the stator has an inner diameter defined by inner ends of the stator teeth and an outer diameter defined by an outer surface of the stator core, a ratio of the inner diameter to the outer diameter being in the range of 0.5 to 0.53, and wherein the stator core has a variable thickness and, for each of the plurality of slots, includes a first portion forming an approximately right angle with the respective stator tooth and a second portion that is substantially normal to a radius of the stator assembly and forms an angle of approximately 25 to 35 degrees with the first portion.
2. The BLDC motor of claim 1 , wherein the stator outer diameter is in the range of 50 mm to 70 mm.
3. The BLDC motor of claim 1 , wherein each of the plurality of slots has an area of greater than or equal to approximately 29 mm{circumflex over ( )}2.
4. The BLDC motor of claim 1 , wherein the second portion of the stator core has a maximum thickness in alignment with a centerline of the slot that is in the range of approximately 3.6 mm to 3.8 mm.
5. The BLDC motor of claim 4 , wherein the second portion of the stator core has a minimum thickness proximate the first portion that is in the range of approximately 3 mm to 3.4 mm.
6. The BLDC motor of claim 5 , wherein each stator tooth has a thickness that is approximately 1.9 to 2.1 times the minimum thickness of the second portion of the stator core.
7. The BLDC motor of claim 1 , wherein each stator winding comprises at least 19 turns of 18 gauge wire.
8. The BLDC motor of claim 1 , wherein each stator winding comprises at least 30 turns of 19.5 gauge wire.
9. The BLDC motor of claim 1 , wherein each stator winding comprises at least 38 turns of 20.5 gauge wire.
10. A power tool comprising:
a housing; and
a brushless direct-current (BLDC) motor disposed within the housing, the motor comprising:
a rotor assembly including rotor shaft extending along a longitudinal axis and a rotor supporting a plurality of magnets mounted on the rotor shaft; and
a stator assembly including a stator comprising a stator core and a plurality of stator teeth radially extending from the stator core and defining a plurality of slots therebetween, and a plurality of stator windings wound on the plurality of stator teeth,
wherein the stator has an inner diameter defined by inner ends of the stator teeth and an outer diameter defined by an outer surface of the stator core, a ratio of the inner diameter to the outer diameter being in the range of 0.5 to 0.53, and wherein the stator core has a variable thickness and, for each of the plurality of slots, includes a first portion forming an approximately right angle with the respective stator tooth and a second portion that is substantially normal to a radius of the stator assembly and forms an angle of approximately 25 to 35 degrees with the first portion.
11. The power tool of claim 10 , wherein the stator outer diameter is in the range of 50 mm to 70 mm.
12. The power tool of claim 10 , wherein each of the plurality of slots has an area of greater than or equal to approximately 29 mm{circumflex over ( )}2.
13. The power tool of claim 10 , wherein the second portion of the stator core has a maximum thickness in alignment with a centerline of the slot that is in the range of approximately 3.6 mm to 3.8 mm.
14. The power tool of claim 13 , wherein the second portion of the stator core has a minimum thickness proximate the first portion that is in the range of approximately 3 mm to 3.4 mm.
15. The power tool of claim 14 , wherein each stator tooth has a thickness that is approximately 1.9 to 2.1 times the minimum thickness of the second portion of the stator core.
16. The power tool of claim 10 , wherein each stator winding comprises at least 19 turns of 18 gauge wire.
17. The power tool of claim 10 , wherein each stator winding comprises at least 30 turns of 19.5 gauge wire.
18. The power tool of claim 10 , wherein each stator winding comprises at least 38 turns of 20.5 gauge wire.
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US17/550,315 US20220200368A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with improved slot fill |
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US202063129797P | 2020-12-23 | 2020-12-23 | |
US17/550,315 US20220200368A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with improved slot fill |
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US20220200368A1 true US20220200368A1 (en) | 2022-06-23 |
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US17/550,341 Pending US20220200388A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with circuit board for winding interconnections |
US17/550,307 Abandoned US20220200401A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with circuit board for winding interconnections |
US17/550,323 Pending US20220200414A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor having high power density for power tool |
US17/550,289 Active US11837926B2 (en) | 2020-12-23 | 2021-12-14 | Brushless DC motor with stator teeth having multiple parallel sets of windings |
US17/550,315 Abandoned US20220200368A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with improved slot fill |
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US17/550,341 Pending US20220200388A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with circuit board for winding interconnections |
US17/550,307 Abandoned US20220200401A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor with circuit board for winding interconnections |
US17/550,323 Pending US20220200414A1 (en) | 2020-12-23 | 2021-12-14 | Brushless dc motor having high power density for power tool |
US17/550,289 Active US11837926B2 (en) | 2020-12-23 | 2021-12-14 | Brushless DC motor with stator teeth having multiple parallel sets of windings |
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US11757321B2 (en) * | 2021-08-18 | 2023-09-12 | GM Global Technology Operations LLC | Rotary electric machine with stator assembly having stator slots lined with multiple molding materials |
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2021
- 2021-12-14 US US17/550,341 patent/US20220200388A1/en active Pending
- 2021-12-14 US US17/550,307 patent/US20220200401A1/en not_active Abandoned
- 2021-12-14 US US17/550,323 patent/US20220200414A1/en active Pending
- 2021-12-14 US US17/550,289 patent/US11837926B2/en active Active
- 2021-12-14 US US17/550,315 patent/US20220200368A1/en not_active Abandoned
- 2021-12-21 EP EP21216339.8A patent/EP4020771A1/en active Pending
- 2021-12-21 EP EP21216342.2A patent/EP4020766A1/en active Pending
- 2021-12-21 EP EP21216332.3A patent/EP4020773A1/en active Pending
- 2021-12-21 EP EP21216265.5A patent/EP4020768A1/en active Pending
- 2021-12-21 EP EP21216266.3A patent/EP4020761A1/en active Pending
Patent Citations (3)
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US6025665A (en) * | 1997-02-21 | 2000-02-15 | Emerson Electric Co. | Rotating machine for use in a pressurized fluid system |
US20190044110A1 (en) * | 2017-07-25 | 2019-02-07 | Milwaukee Electric Tool Corporation | High power battery-powered system |
JP2020171178A (en) * | 2019-04-05 | 2020-10-15 | 株式会社ミツバ | Brushless motor |
Non-Patent Citations (1)
Title |
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JP2020171178A English translation (Year: 2023) * |
Also Published As
Publication number | Publication date |
---|---|
US20220200414A1 (en) | 2022-06-23 |
US20220200388A1 (en) | 2022-06-23 |
EP4020771A1 (en) | 2022-06-29 |
EP4020766A1 (en) | 2022-06-29 |
EP4020761A1 (en) | 2022-06-29 |
US20220200401A1 (en) | 2022-06-23 |
US20220200426A1 (en) | 2022-06-23 |
EP4020773A1 (en) | 2022-06-29 |
EP4020768A1 (en) | 2022-06-29 |
US11837926B2 (en) | 2023-12-05 |
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