Balance ring for a vehicular electric machine

Abstract

An electric machine for deployment in a vehicle, with the electric machine having a housing is provided. The electric machine comprises a stator assembly coupled to the housing, and a rotor assembly disposed within the stator assembly and configured to rotate relative thereto. A balance ring is coupled to an end of the rotor assembly and is configured to rotate therewith. The balance ring comprises an annular base layer having a first planar surface, and an annular magnetic shielding layer having a second planar surface clad to the first planar surface

1 . An electric machine for deployment in a vehicle, the electric machine having a housing, the electric machine comprising:
 a stator assembly coupled to the housing;   a rotor assembly disposed within the stator assembly and configured to rotate relative thereto; and   a balance ring coupled to an end of the rotor assembly and configured to rotate therewith, the balance ring comprising:
 an annular base layer having a first planar surface; and 
 an annular magnetic shielding layer having a second planar surface clad to the first planar surface. 
   
     
     
         2 . An electric machine according to  claim 1 , wherein the annular magnetic shielding layer further comprises a third planar surface coupled adjacent the end of the rotor assembly. 
     
     
         3 . An electric machine according to  claim 1 , wherein the annular magnetic shielding layer comprises a material selected from a group consisting of titanium, aluminum, stainless steel, copper, magnesium, chromium, zinc, manganese, molybdenum, and alloys thereof. 
     
     
         4 . An electric machine according to  claim 1 , wherein the annular base layer comprises carbon steel. 
     
     
         5 . An electric machine according to  claim 1 , wherein the annular magnetic shielding layer has a magnetic permeability of from about 1 to about 2 times the magnetic permeability of a vacuum. 
     
     
         6 . An electric machine according to  claim 5 , wherein the annular magnetic shielding layer has a magnetic permeability of from about 1 to about 1.2 times the magnetic permeability of a vacuum. 
     
     
         7 . An electric machine according to  claim 1 , wherein the annular base layer has a thickness of from about 1 mm to about 20 mm. 
     
     
         8 . An electric machine according to  claim 1 , wherein the annular magnetic shielding layer has a thickness of from about 0.1 mm to about 10 mm. 
     
     
         9 . A balance ring comprising:
 a first annular layer comprised of a high strength material, the first annular layer having a first planar surface; and   a second annular layer comprised of a low magnetic permeability material, the second annular layer having a second planar surface clad to the first planar surface.   
     
     
         10 . A balance ring according to  claim 9 , wherein the second annular layer has a composition selected from a group consisting of titanium, aluminum, stainless steel, copper, magnesium, chromium, zinc, manganese, molybdenum, and alloys thereof. 
     
     
         11 . A balance ring according to  claim 9 , wherein the first annular layer comprises carbon steel. 
     
     
         12 . A balance ring according to  claim 9 , wherein the second annular layer has a magnetic permeability of from about 1 to about 2 times the magnetic permeability of a vacuum. 
     
     
         13 . A balance ring according to  claim 12 , wherein the second annular layer has a magnetic permeability of from about 1 to about 1.2 times the magnetic permeability of a vacuum. 
     
     
         14 . A method for fabricating a balance ring for a vehicular electric machine, the method comprising the steps of:
 providing a first metal layer having a first planar surface;   providing a second metal layer having a second planar surface;   cladding the second planar surface to the first planar surface to form a composite structure; and   removing a portion of the composite structure to form an annular ring.   
     
     
         15 . A method according to  claim 14 , wherein the step of providing a second metal layer comprises providing a second metal layer comprised of a low magnetic permeability material. 
     
     
         16 . A method according to  claim 15 , wherein the step of providing a second metal layer comprised of a low magnetic permeability material comprises providing a second metal layer comprised of a material having a magnetic permeability of from about 1 to about 2 times the magnetic permeability of a vacuum. 
     
     
         17 . A method according to  claim 14 , wherein the step of removing comprises removing by stamping. 
     
     
         18 . A method according to  claim 15 , wherein the step of providing a second metal layer comprised of a material having a low magnetic permeability comprises providing a second metal layer comprised of aluminum. 
     
     
         19 . A method according to  claim 14 , further comprising the step of machining the annular ring to form the balance ring. 
     
     
         20 . A method according to  claim 19 , wherein the vehicular electric machine further comprises a rotor having an end, and further comprising the step of mounting the balance ring on the end of the rotor.