Rotor assembly

Abstract

A rotor assembly that includes a shaft to which are mounted an impeller, a rotor core and a bearing cartridge. The bearing cartridge is mounted between the impeller and the rotor core and comprises a pair of bearings, a spring that applies a preload to each of the bearings, and a sleeve that surrounds the bearings.

1 . A rotor assembly comprising a shaft to which are mounted an impeller, a rotor core and a bearing cartridge, the bearing cartridge being mounted between the impeller and the rotor core and comprising a pair of bearings, a spring applying a preload to each of the bearings and a sleeve surrounding the bearings. 
   
   
       2 . A rotor assembly as claimed in  claim 1 , wherein the sleeve has a coefficient of thermal expansion substantially matching that of the shaft. 
   
   
       3 . A rotor assembly as claimed in  claim 1 , wherein the sleeve is formed of an electrically insulating material. 
   
   
       4 . A rotor assembly as claimed in  claim 1 , wherein the sleeve is formed of a non-magnetic material. 
   
   
       5 . A rotor assembly as claimed in  claim 1 , wherein the centre of mass of the rotor assembly is located within the bearing cartridge. 
   
   
       6 . A rotor assembly as claimed in  claim 1 , wherein the rotor assembly comprises a spacer that surrounds the shaft, separates the two bearings and contributes to the shaft stiffness. 
   
   
       7 . A rotor assembly as claimed in  claim 6 , wherein the bearings and the spacer have a coefficient of thermal expansion substantially matching that of the shaft. 
   
   
       8 . A rotor assembly as claimed in  claim 1 , wherein the shaft is formed of a soft magnetic material. 
   
   
       9 . A rotor assembly as claimed in  claim 1 , wherein the rotor assembly comprises a dirt cap that covers an annular gap in the bearing adjacent the rotor core, the dirt cap being secured to the shaft and comprising a flange that extends radially outward from the shaft to cover the annular gap. 
   
   
       10 . A rotor assembly comprising a bearing cartridge mounted to a shaft, the bearing cartridge comprising a pair of bearings, a spring applying a preload to each of the bearings, and a sleeve surrounding the bearings, wherein the sleeve has a coefficient of thermal expansion substantially matching that of the shaft. 
   
   
       11 . A rotor assembly as claimed in  claim 10 , wherein the sleeve is formed of an electrically insulating material. 
   
   
       12 . A rotor assembly as claimed in  claim 10 , wherein the sleeve is formed of a non-magnetic material. 
   
   
       13 . A rotor assembly as claimed in  claim 10 , wherein the shaft is formed of a soft magnetic material. 
   
   
       14 . A rotor assembly as claimed in  claim 10 , wherein the rotor assembly comprises a spacer that surrounds the shaft, separates the two bearings and contributes to the shaft stiffness. 
   
   
       15 . A rotor assembly as claimed in  claim 14 , wherein the bearings and the spacer have a coefficient of thermal expansion substantially matching that of the shaft. 
   
   
       16 . A rotor assembly as claimed in  claim 10 , wherein the rotor assembly comprises a dirt cap that covers an annular gap in one of the bearings, the dirt cap being secured to the shaft and comprising a flange that extends radially outward from the shaft to cover the annular gap. 
   
   
       17 . A rotor assembly comprising a bearing cartridge mounted to a shaft, the bearing cartridge comprising a pair of bearings, a spring applying a preload to each of the bearings, and a sleeve surrounding the bearings, wherein the sleeve is formed of an electrically insulating material. 
   
   
       18 . A rotor assembly as claimed in  claim 17 , wherein the sleeve is formed of a non-magnetic material.