# US 12,184,149 B2 · Electric motor for a handheld power tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,149 B2 - Document ID: US12184149B2 - Status: Granted - Kind: B2 - Application number: 17/837,599 - Filed: 2022-06-10 - Published: 2022-09-22 - Granted: 2024-12-31 - Earliest claimed: 2019-12-13 - Assignees: C. & E. Fein GmbH - Applicants: C. & E. Fein GmbH - Inventors: Martin Adamczyk; Christoph Maier; Rudi Brueckmann; Bernd Mayer; Tobias Hokenmaier - Web page: https://patentgrep.com/patent/US12184149B2 ## CPC - H02K 5/18: with ribs or fins for improving heat transfer - H02K 5/08: Insulating casings - H02K 5/15: Mounting arrangements for bearing-shields or end plates - H02K 5/1732: {radially supporting the rotary shaft at both ends of the rotor (H02K5/1737 takes precedence)} - H02K 7/003: {Couplings; Details of shafts (means for mounting rotors on shafts H02K1/28)} - H02K 7/145: {Hand-held machine tool} - H02K 9/06: with fans or impellers driven by the machine shaft - H02K 11/21: Devices for sensing speed or position, or actuated thereby (specially adapted for machines having non-mechanical commutating devices H02K29/06, H02K29/14) - 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 An electric motor of an AC-operated, handheld power tool, with a stator that has multiple windings that are accommodated in a laminated stator core and are electrically insulated therefrom with basic insulation, in which stator a rotor is supported so as to be rotatable about an axis of rotation, wherein the rotor has a rotor shaft on which a laminated rotor core with a multiplicity of permanent magnets is held, which laminated rotor core is electrically insulated from the rotor shaft, characterized in that the stator is enclosed by a motor housing that is electrically insulated from the windings of the stator, and in that a supplementary electrical insulation is formed between the motor housing and the rotor shaft. ## Claims ### Claim 1 An electric motor of an AC-operated handheld power tool, the electric motor comprising: a stator that has a plurality of windings that are accommodated in a laminated stator core and are electrically insulated therefrom with insulation; and a rotor supported in the stator so as to be rotatable about an axis of rotation, the rotor having a rotor shaft on which a laminated rotor core with at least two permanent magnets is held, wherein the laminated rotor core is electrically insulated from the rotor shaft, wherein the stator is enclosed by a motor housing that is electrically insulated from the windings of the stator, wherein a supplementary electrical insulation is formed between the motor housing and the rotor shaft, wherein the supplementary electrical insulation includes an electrically insulating bearing retaining sleeve in which the rotor shaft is accommodated, and wherein the bearing retaining sleeve has a radial rib on an inner circumferential side, such that the radial rib protrudes inward from an inner circumferential surface of the bearing retaining sleeve in a direction towards the rotor shaft. ### Claim 2 (depends on 1) The electric motor according to claim 1, wherein the bearing retaining sleeve has a first bearing seat for a first bearing of the rotor shaft, such that the first bearing is accommodated inside of the bearing retaining sleeve. ### Claim 3 (depends on 1) The electric motor according to claim 1, wherein the bearing retaining sleeve has a collar on an outer circumferential side. ### Claim 4 (depends on 1) The electric motor according to claim 1, wherein the supplementary electrical insulation includes an end cap that delimits the motor housing in an axial direction. ### Claim 5 (depends on 4) The electric motor according to claim 4, wherein the end cap is made at least partially of an electrically insulating material. ### Claim 6 (depends on 4) The electric motor according to claim 4, wherein the end cap and the motor housing are connected to one another or are detachably connected to one another. ### Claim 7 (depends on 6) The electric motor according to claim 6, wherein the supplementary electrical insulation includes an electrically insulating bearing retaining sleeve in which the rotor shaft is accommodated, wherein the bearing retaining sleeve has a first bearing seat for a first bearing of the rotor shaft, and wherein a second bearing seat, in which a second bearing of the rotor shaft is accommodated, is formed in the end cap. ### Claim 8 (depends on 1) The electric motor according to claim 1, wherein the motor housing is matched to the stator such that a thermal contact of an inner wall of the motor housing and an outer wall of the stator is realized. ### Claim 9 (depends on 1) The electric motor according to claim 1, wherein the motor housing is made of metal. ### Claim 10 (depends on 1) The electric motor according to claim 1, wherein cooling fins are associated with the motor housing on an outer circumferential side. ### Claim 11 (depends on 10) The electric motor according to claim 10, wherein a ratio of a diameter of the motor housing to a height of the cooling fins is 2:1 to 15:1. ### Claim 12 (depends on 10) The electric motor according to claim 10, wherein the cooling fins are arranged radially, and radially outer ends of the cooling fins have a constant distance from the axis of rotation of the rotor. ### Claim 13 (depends on 1) The electric motor according to claim 1, wherein a contact face, in which a heat-conducting ring is accommodated, is formed in the motor housing. ### Claim 14 (depends on 1) The electric motor according to claim 1, wherein an auxiliary fan is arranged on the rotor shaft inside the electric motor. ### Claim 15 (depends on 1) The electric motor according to claim 1, wherein the supplementary electrical insulation is an insulation arranged on the rotor shaft. ### Claim 16 (depends on 1) A handheld electric power tool or a grinding tool for working workpieces comprising a housing in which the electric motor according to claim 1 is accommodated. ### Claim 17 An electric motor of an AC-operated handheld power tool, the electric motor comprising: a stator that has a plurality of windings that are accommodated in a laminated stator core and are electrically insulated therefrom with insulation; and a rotor supported in the stator so as to be rotatable about an axis of rotation, the rotor having a rotor shaft on which a laminated rotor core with at least two permanent magnets is held, wherein the laminated rotor core is electrically insulated from the rotor shaft, wherein the stator is enclosed by a motor housing that is electrically insulated from the windings of the stator, wherein a supplementary electrical insulation is formed between the motor housing and the rotor shaft, wherein the supplementary electrical insulation includes an end cap that delimits the motor housing in an axial direction, and wherein a mounting flange, in which a part of a position sensor is accommodated for determining a rotational position of the rotor shaft, is formed in the end cap. ### Claim 18 An electric motor of an AC-operated handheld power tool, the electric motor comprising: a stator that has a plurality of windings that are accommodated in a laminated stator core and are electrically insulated therefrom with insulation; and a rotor supported in the stator so as to be rotatable about an axis of rotation, the rotor having a rotor shaft on which a laminated rotor core with at least two permanent magnets is held, wherein the laminated rotor core is electrically insulated from the rotor shaft, wherein the stator is enclosed by a motor housing that is electrically insulated from the windings of the stator, wherein a supplementary electrical insulation is formed between the motor housing and the rotor shaft wherein a contact face, in which a heat-conducting ring is accommodated, is formed in the motor housing, and wherein the heat-conducting ring is elastically deformable.