# US 10,320,274 B2 · Combination structure between stator and rotor in a brushless motor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,320,274 B2 - Document ID: US10320274B2 - Status: Granted - Kind: B2 - Application number: 15/210,517 - Filed: 2016-07-14 - Published: 2017-01-19 - Granted: 2019-06-11 - Earliest claimed: 2015-07-16 - Assignees: Bergstrom, Inc. - Applicants: Bergstrom, Inc. - Inventors: Kuilin Yang; Gengxiang Li; Lei Wang - Web page: https://patentgrep.com/patent/US10320274B2 ## CPC - H02K 29/03: with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems - H02K 1/2766: {having a flux concentration effect} - H02K 1/146: {consisting of a generally annular yoke with salient poles} - H02K 2201/03: Machines characterised by aspects of the air-gap between rotor and stator - H02K 2213/03: Machines characterised by numerical values, ranges, mathematical expressions or similar information - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract A brushless motor includes a stator having stator core and winding teeth evenly distributed on the stator core; and a rotor rotatably disposed within the stator with the winding teeth facing the rotor, where the rotor has a rotor core and magnets evenly distributed around the rotor core. A first symmetry axis is defined passing through a center of a one of the magnets to a center of the rotor, and a second symmetry axis is defined passing between adjacent magnets to the center of the rotor. A first distance between the outer surface of the rotor to a surface of a winding tooth when the first axis is aligned with the winding tooth is smaller than a second distance between the outer surface of the rotor to the surface of the winding tooth when the second axis is aligned with the winding tooth. ## Claims ### Claim 1 A brushless motor, comprising: a stator including a stator core and a plurality of winding teeth evenly distributed on the stator core; and a rotor rotatably disposed within the stator with the winding teeth facing the rotor, the rotor including a rotor core and a plurality of magnets evenly distributed around the rotor core, wherein a first symmetry axis is defined passing through a center of a first one of the magnets to a center of the rotor, and a second symmetry axis is defined passing between adjacent ones of the magnets to the center of the rotor, wherein a first distance between an outer surface of the rotor to a surface of a first one of the winding teeth when the first axis is aligned with the first winding tooth is smaller than a second distance between the outer surface of the rotor to the surface of the first winding tooth when the second axis is aligned with the first winding tooth, wherein each winding tooth includes a coil wound portion and a front portion facing the rotor at an end of the coil wound portion, wherein a surface of the front portion has an arc segment at a center part and two straight line segments connected to respective ends of the arc segment, and wherein a length of each straight line segment, a width of the winding portion, and a width of the front portion are configured to satisfy: (c−b)/2≤a≤c/2 where ‘a’ is the length of each straight line segment, ‘b’ is the width of the winding portion, and ‘c’ is the width of the front part. ### Claim 2 (depends on 1) The brushless motor according to claim 1, wherein a distance between the outer surface of the rotor to the surface of the first winding tooth becomes smaller as the rotor rotates from a state with the second axis being aligned with the first tooth to a state with the first axis being aligned with the first tooth. ### Claim 3 (depends on 1) The brushless motor according to claim 1, wherein a distance between the outer surface of the rotor to the surface of the first winding tooth becomes continuously smaller as the rotor rotates from a state with the second axis being aligned with the first tooth to a state with the first axis being aligned with the first tooth. ### Claim 4 (depends on 1) The brushless motor according to claim 1, wherein the rotor and the stator are configured such that the first and second distances satisfy 1.5≤g2/g1≤3.5 where g1 is the first distance and g2 is the second distance. ### Claim 5 (depends on 1) A brushless motor according to claim 1, wherein the outer surface of the rotor includes alternating circular arc segments and curved inward V shaped segments that are smoothly connected, wherein the first axis passes through a center of one of the circular arc segments, and wherein the second axis passes through a center of one of the curved inward V shaped segments. ### Claim 6 (depends on 5) A brushless motor according to claim 5, wherein each of the circular arc segments has an arc radius R1 which is greater than a distance R2 defined from a center of the circular arc segment to a center of the rotor. ### Claim 7 (depends on 5) A brushless motor according to claim 5, wherein an angle of each of the circular arc segments relative to the center of the rotor satisfies 0.444≤θ1/(360°/P)≤0.665 where θ1 is the angle and P is the number of magnets distributed around the rotor core. ### Claim 8 (depends on 1) The brushless motor according to claim 1, wherein a stator slot is defined between two adjacent winding teeth portions, wherein a base of the stator slot includes an arc segment and two straight lines connected to respective ends of the arc segment, and wherein each straight line segment is perpendicular to and smoothly connected to an adjacent side wall of the coil wound portion. ### Claim 9 (depends on 1) The brushless motor according to claim 1, wherein a ratio of a number of winding teeth to a number of poles distributed around the rotor core is 3:2. ### Claim 10 (depends on 1) The brushless motor according to claim 1, wherein magnets are disposed in mounting slots evenly distributed around the rotor core. ### Claim 11 (depends on 10) The brushless motor according to claim 10, wherein the rotor core includes rotor lamination, and wherein the stator core includes stator lamination. ### Claim 12 (depends on 11) The brushless motor according to claim 11, wherein a length of each mounting slot is greater than a length of each respective magnet, and each magnet is disposed at a center of each mounting slot, wherein flux barriers are at each side of each respective mounting slot, and wherein a width of the flux barrier is 1.5˜3 times of the thickness of the rotor lamination. ### Claim 13 (depends on 10) The brushless motor according to claim 10, wherein the magnets are fastened into respective ones of the mounting slots by a fastening clip. ### Claim 14 (depends on 1) The brushless motor according to claim 1, wherein the magnets are along an outer surface of the rotor to be within the rotor inside of the outer surface. ### Claim 15 A brushless motor, comprising: a stator including a stator core and a plurality of winding teeth evenly distributed on the stator core; and a rotor rotatably disposed within the stator with the winding teeth facing the rotor, the rotor including a rotor core and a plurality of magnets evenly distributed around the rotor core, wherein a first symmetry axis is defined passing through a center of a first one of the magnets to a center of the rotor, and a second symmetry axis is defined passing between adjacent ones of the magnets to the center of the rotor, wherein a first distance between an outer surface of the rotor to a surface of a first one of the winding teeth when the first axis is aligned with the first winding tooth is smaller than a second distance between the outer surface of the rotor to the surface of the first winding tooth when the second axis is aligned with the first winding tooth, wherein the rotor and the stator are configured such that the first and second distances satisfy: 1.5≤g2/g1≤3.5 where g1 is the first distance and g2 is the second distance, wherein magnets are disposed in mounting slots evenly distributed around the rotor core, wherein a length of each mounting slot is greater than a length of each respective magnet, and each magnet is disposed at a center of each mounting slot, wherein flux barriers are at each side of each respective mounting slot, wherein each winding tooth includes a coil wound portion and a front portion facing the rotor at an end of the coil wound portion, wherein a surface of the front portion has an arc segment at a center part and two straight line segments connected to respective ends of the arc segment, and wherein a length of each straight line segment, a width of the winding portion, and a width of the front portion are configured to satisfy: (c−b)/2≤a≤c/2 where ‘a’ is the length of each straight line segment, ‘b’ is the width of the winding portion, and ‘c’ is the width of the front part. ### Claim 16 (depends on 15) The brushless motor according to claim 15, wherein a distance between the outer surface of the rotor to the surface of the first winding tooth becomes smaller as the rotor rotates from a state with the second axis being aligned with the first tooth to a state with the first axis being aligned with the first tooth. ### Claim 17 (depends on 15) The brushless motor according to claim 15, wherein a distance between the outer surface of the rotor to the surface of the first winding tooth becomes continuously smaller as the rotor rotates from a state with the second axis being aligned with the first tooth to a state with the first axis being aligned with the first tooth. ### Claim 18 (depends on 15) The brushless motor according to claim 15, wherein the outer surface of the rotor includes alternating circular arc segments and curved inward V shaped segments that are smoothly connected, wherein the first axis passes through a center of one of the circular arc segments, and wherein the second axis passes through a center of one of the curved inward V shaped segments, wherein each of the circular arc segments has an arc radius R1 which is greater than a distance R2 defined from a center of the circular arc segment to a center of the rotor, and wherein an angle of each of the circular arc segments relative to the center of the rotor satisfies 0.444≤θ1/(360°/P)≤0.665 where θ1 is the angle and P is the number of magnets distributed around the rotor core. ### Claim 19 (depends on 15) The brushless motor according to claim 15, wherein a stator slot is defined between two adjacent winding teeth portions, wherein a base of the stator slot includes an arc segment and two straight lines connected to respective ends of the arc segment, and wherein each straight line segment is perpendicular to and smoothly connected to an adjacent side wall of the coil wound portion.