# US 2017/0288494 A1 · Spindle motor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0288494 A1 - Document ID: US20170288494A1 - Status: Published application - Kind: A1 - Application number: 15/472,385 - Filed: 2017-03-29 - Published: 2017-10-05 - Earliest claimed: 2016-03-31 - Assignees: MINEBEA MITSUMI Inc. - Applicants: Minebea Mitsumi Inc. - Inventors: Hideaki SHOWA; Daigo NAKAJIMA; Naoyuki KONDO - Web page: https://patentgrep.com/patent/US20170288494A1 ## CPC - H02K 5/22: Auxiliary parts of casings not covered by groups H02K5/06-H02K5/20, e.g. shaped to form connection boxes or terminal boxes - G11B 19/2036: {Motors characterized by fluid-dynamic bearings} - H02K 1/2791: Surface mounted magnets; Inset magnets - H02K 7/09: with magnetic bearings - 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}) - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A spindle motor has a base plate, a stator core fixed to the base plate, a rotor member rotatable with respect to the base plate, a rotor magnet facing the stator core in a radial direction and fixed to the rotor member and a ring-shaped magnetic attractive plate attached to the base plate bottom surface facing the rotor magnet in an axial direction to generate a magnetic attracting force between the rotor magnet and the magnetic attractive plate. A ring-shaped wall surface is on the base plate bottom surface. At least one of an outer and inner circumference of the ring-shaped magnetic attractive plate has a polygonal shape formed of linear parts and corner parts. In a state in which at least one of the outer and inner circumferences having the polygonal shape contacts the ring-shaped wall surface, the ring-shaped magnetic attractive plate is adhesively fixed to the base plate. ## Claims ### Claim 1 A spindle motor comprising: a base plate; a stator core fixed to the base plate; a rotor member rotatable with respect to the base plate; a rotor magnet facing the stator core in a radial direction and fixed to the rotor member; and a ring-shaped magnetic attractive plate attached to a bottom surface of the base plate in a manner to face the rotor magnet in an axial direction and configured to generate a magnetic attracting force between the rotor magnet and the magnetic attractive plate, wherein a ring-shaped wall surface is provided on the bottom surface of the base plate, at least one of an outer circumference and an inner circumference of the ring-shaped magnetic attractive plate has a polygonal shape formed of a plurality of linear parts and a plurality of corner parts, and the ring-shaped magnetic attractive plate is fixed to the base plate with an adhesive in a condition that at least one of the outer circumference and the inner circumference having the polygonal shape is in contact with the ring-shaped wall surface. ### Claim 2 (depends on 1) The spindle motor according to claim 1, wherein the number of the corner parts in the polygonal shape of the magnetic attractive plate is a prime number. ### Claim 3 (depends on 2) The spindle motor according to claim 2, wherein the prime number is any one of 7, 11, 13, 17 and 19. ### Claim 4 (depends on 1) The spindle motor according to claim 1, wherein a portion of the magnetic attractive plate where at least one of the outer circumference and the inner circumference having the polygonal shape is in contact with the ring-shaped wall surface is fitted by an interference fit or transition fit. ### Claim 5 (depends on 1) The spindle motor according to claim 1, wherein the outer circumference or the inner circumference of the magnetic attractive plate is circular. ### Claim 6 (depends on 1) The spindle motor according to claim 1, wherein the same number of corner parts are formed on the inner circumference and the outer circumference of the magnetic attractive plate. ### Claim 7 (depends on 1) The spindle motor according to claim 1, wherein the outer circumference and the inner circumference of the magnetic attractive plate have roll-over portions on the same side in the axial direction and the magnetic attractive plate is fixed with the side with the roll-over portions facing the bottom surface of the base plate. ### Claim 8 (depends on 1) The spindle motor according to claim 1, wherein the outer circumference of the magnetic attractive plate having the polygonal shape when viewed from the axial direction is located outside the outer diameter of the rotor magnet in the radial direction. ### Claim 9 (depends on 1) The spindle motor according to claim 1, wherein the inner circumference of the magnetic attractive plate having the polygonal shape when viewed from the axial direction is located inside the inner diameter of the rotor magnet in the radial direction.