# US 8,766,468 B1 · Rotor for a permanent magnet electrical machine of a mobile working machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,766,468 B1 - Document ID: US8766468B1 - Status: Granted - Kind: B1 - Application number: 13/755,187 - Filed: 2013-01-31 - Granted: 2014-07-01 - Earliest claimed: 2013-01-31 - Assignees: Visedo Oy - Applicants: Visedo Oy - Inventors: Marko Rilla; Timo Päivinen - Web page: https://patentgrep.com/patent/US8766468B1 ## CPC - H02K 1/2773: {consisting of tangentially magnetized radial magnets} - B60L 3/0023: {Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train} - B60L 3/0061: {relating to electrical machines} - B60L 15/20: for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed - B60L 50/40: using propulsion power supplied by capacitors - B60L 50/61: by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles - H02K 9/197: in which the rotor or stator space is fluid-tight, e.g. to provide for different cooling media for rotor and stator - B60L 2200/36: Vehicles designed to transport cargo, e.g. trucks - B60L 2200/40: Working vehicles - B60L 2210/20: AC to AC converters - B60L 2210/30: AC to DC converters - B60L 2210/40: DC to AC converters - B60L 2220/44: Wheel Hub motors, i.e. integrated in the wheel hub - B60L 2220/50: Structural details of electrical machines - B60L 2240/36: Temperature of vehicle components or parts - B60L 2240/421: Speed - B60L 2240/423: Torque - B60L 2250/24: by lever actuation - B60L 2260/28: Four wheel or all wheel drive - Y02T 10/62: Hybrid vehicles - Y02T 10/64: Electric machine technologies in electromobility - Y02T 10/70: Energy storage systems for electromobility, e.g. batteries - Y02T 10/7072: Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors - Y02T 10/72: Electric energy management in electromobility - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A rotor for a permanent magnet electrical machine includes a ferromagnetic core structure having cavities which divide the ferromagnetic core structure into pole regions (103), a yoke region (104), and bridges (105, 106) between them. The rotor includes permanent magnets (107, 108) located in the cavities and arranged to produce magnetic fluxes penetrating the pole regions so as to form magnetic poles of the rotor. The cavities have portions which extend towards the quadrature-axis (Q) and are free from the permanent magnets. Thus, non-ferromagnetic regions for reducing leakage fluxes of the permanent magnets are being formed. Furthermore, the portions of the cavities have a shape curving towards the geometrical rotation axis of the rotor. As the portions of the cavities have the shape curving towards the rotation axis, the cavities can be made longer and the routes of the leakage. ## Claims ### Claim 1 A rotor for a permanent magnet electrical machine, the rotor comprising: a ferromagnetic core structure comprising cavities dividing the ferromagnetic core structure into pole regions, a yoke region, and bridges between the pole regions and the yoke region, and permanent magnets located in the cavities and arranged to produce magnetic fluxes penetrating the pole regions in radial directions so as to form magnetic poles of the rotor, the direction of the magnetic flux penetrating each pole region defining a direct-axis of the corresponding magnetic pole and a symmetry line between direct-axes of two adjacent magnetic poles defining a quadrature-axis between these two adjacent magnetic poles, wherein the cavities have portions which extend towards the quadrature-axis and are free from the permanent magnets so as to form non-ferromagnetic regions for reducing leakage fluxes of the permanent magnets, and the portions of the cavities have a shape curving towards a geometrical rotation axis of the rotor and radial height of the portions of the cavities is greater than radial thickness of parts of the permanent magnets abutting on the portions of the cavities, and wherein the ferromagnetic core structure defining the portions of the cavities and facing towards the non-ferromagnetic regions have profiles in a plane perpendicular to the geometrical rotation axis of the rotor so that: a) each of the profiles is curvilinear on a portion of the profile from a first point of the profile farthest from the geometrical rotation axis of the rotor to a second point of the profile nearest to the geometrical rotation axis of the rotor, b) the radius of curvature of each of the profiles depends on distance to the geometrical rotation axis of the rotor so that the radius of curvature is an ascending function of the distance on the portion of the profile from the first point of the profile to the second point of the profile, and c) each of the profiles is substantially tangentially directed and meets the relevant permanent magnet at the first point of the profile. ### Claim 2 (depends on 1) A rotor according to claim 1, wherein the permanent magnets are rectangular prisms, a direction of magnetization of each permanent magnet is substantially perpendicular to two mutually opposite facets of that permanent magnet, and a spatial line via a center of mass of that permanent magnet and perpendicular to the two mutually opposite facets of that permanent magnet is substantially radially directed. ### Claim 3 (depends on 2) A rotor according to claim 2, wherein the number of the permanent magnets per the number of the magnetic poles of the rotor is two. ### Claim 4 (depends on 1) A rotor according to claim 1, wherein the ferromagnetic core structure comprises grooves on its outer surface between adjacent magnetic poles of the rotor for narrowing the bridges which are tangentially as outmost in each magnetic pole of the rotor so as to reduce the leakage fluxes of the permanent magnets. ### Claim 5 (depends on 4) A rotor according to claim 4, wherein there are two grooves between adjacent magnetic poles of the rotor so that there is a ridge between these two grooves so as to increase a quadrature-axis inductance. ### Claim 6 (depends on 1) A rotor according to claim 1, wherein the number of the magnetic poles of the rotor is at least ten. ### Claim 7 (depends on 1) A rotor according to claim 1, wherein the ferromagnetic core structure comprises ferromagnetic steel sheets stacked in the direction of the geometrical rotation axis of the rotor. ### Claim 8 (depends on 1) A rotor according to claim 1, wherein the ferromagnetic core structure is made of solid steel. ### Claim 9 (depends on 1) A rotor according to claim 1, wherein the radial height of the portions of the cavities is at least 10% greater than the radial thickness of the parts of the permanent magnets abutting on the portions of the cavities. ### Claim 10 (depends on 2) A rotor according to claim 2, wherein corners of the bridges between adjacent permanent magnets of each magnetic pole of the rotor comprise roundings that extend away from the respective corners of the permanent magnets so as to form non-ferromagnetic regions for reducing leakage fluxes of the permanent magnets. ### Claim 11 (depends on 2) A rotor according to claim 2, wherein the ferromagnetic core structure comprises grooves on its outer surface between adjacent magnetic poles of the rotor for narrowing the bridges which are tangentially as outmost in each magnetic pole of the rotor so as to reduce the leakage fluxes of the permanent magnets. ### Claim 12 (depends on 3) A rotor according to claim 3, wherein the ferromagnetic core structure comprises grooves on its outer surface between adjacent magnetic poles of the rotor for narrowing the bridges which are tangentially as outmost in each magnetic pole of the rotor so as to reduce the leakage fluxes of the permanent magnets. ### Claim 13 A mobile working machine comprising: a combustion engine, and an electromechanical power transmission chain between the combustion engine and one or more wheels of the mobile working machine, wherein the electromechanical transmission chain comprises at least one permanent magnet electrical machine comprising a rotor and a stator, the rotor comprising: a ferromagnetic core structure comprising cavities dividing the ferromagnetic core structure into pole regions, a yoke region, and bridges between the pole regions and the yoke region, and permanent magnets located in the cavities and arranged to produce magnetic fluxes penetrating the pole regions in radial directions so as to form magnetic poles of the rotor, the direction of the magnetic flux penetrating each pole region defining a direct-axis of the corresponding magnetic pole and a symmetry line between direct-axes of two adjacent magnetic poles defining a quadrature-axis between these two adjacent magnetic poles, wherein the cavities have portions which extend towards the quadrature-axis and are free from the permanent magnets so as to form non-ferromagnetic regions for reducing leakage fluxes of the permanent magnets, and the portions of the cavities have a shape curving towards a geometrical rotation axis of the rotor and radial height of the portions of the cavities is greater than radial thickness of parts of the permanent magnets abutting on the portions of the cavities, and wherein the ferromagnetic core structure defining the portions of the cavities and facing towards the non-ferromagnetic regions have profiles in a plane perpendicular to the geometrical rotation axis of the rotor so that: a) each of the profiles is curvilinear on a portion of the profile from a first point of the profile farthest from the geometrical rotation axis of the rotor to a second point of the profile nearest to the geometrical rotation axis of the rotor, b) the radius of curvature of each of the profiles depends on distance to the geometrical rotation axis of the rotor so that the radius of curvature is an ascending function of the distance on the portion of the profile from the first point of the profile to the second point of the profile, and c) each of the profiles is substantially tangentially directed and meets the relevant permanent magnet at the first point of the profile. ### Claim 14 (depends on 13) A mobile working machine according to claim 13, wherein the mobile working machine comprises a liquid cooling system arranged to cool the electromechanical power transmission chain. ### Claim 15 (depends on 14) A mobile working machine according to claim 14, wherein the liquid cooling system is arranged to cool both the electromechanical power transmission chain and a hydraulic system of the mobile working machine. ### Claim 16 (depends on 14) A mobile working machine according to claim 14, wherein the liquid cooling system is arranged to cool both the electromechanical power transmission chain and the combustion engine. ### Claim 17 (depends on 13) A mobile working machine according to claim 13, wherein the electromechanical power transmission chain comprises at least one of the following for responding to peak power needs exceeding the maximum power of the combustion engine: a battery, an electric double-layer capacitor. ### Claim 18 (depends on 14) A mobile working machine according to claim 14, wherein the electromechanical power transmission chain comprises at least one of the following for responding to peak power needs exceeding the maximum power of the combustion engine: a battery, an electric double-layer capacitor. ### Claim 19 (depends on 15) A mobile working machine according to claim 15, wherein the electromechanical power transmission chain comprises at least one of the following for responding to peak power needs exceeding the maximum power of the combustion engine: a battery, an electric double-layer capacitor. ### Claim 20 (depends on 16) A mobile working machine according to claim 16, wherein the electromechanical power transmission chain comprises at least one of the following for responding to peak power needs exceeding the maximum power of the combustion engine: a battery, an electric double-layer capacitor.