Turbomolecular vacuum pump

Abstract

A turbomolecular pump comprises a pumping mechanism and an electric motor ( 10 ) for driving the pumping mechanism. The electric motor comprises a rotor ( 14 ), a stator and stator windings ( 20 ). The stator comprises a yoke [ 18 ( 1 ), 18 ( 2 )] and a plurality of teeth ( 16 ) projecting from the yoke and carrying the stator windings. The yoke and the teeth are made of a non-sintered magnetic powder material in which the powder particles are bonded by an electrically insulating binder.

1 . A turbomolecular vacuum pump comprising a pumping mechanism and an electric motor for driving the pumping mechanism, the electric motor comprising a rotor, a stator and stator windings, the stator comprising a yoke and a plurality of teeth projecting from the yoke and carrying the stator windings, the yoke and the teeth being made of a non-sintered magnetic powder material in which particles in the powder material are bonded by an electrically insulating binder.  
     
     
         2 . The pump according to  claim 1  wherein the stator comprises three of the teeth.  
     
     
         3 . The pump according to  claim 1 , wherein the stator windings are non-distributed windings.  
     
     
         4 . The pump according to  claim 1  wherein the rotor comprises a permanent magnet.  
     
     
         5 . The pump according to  claim 4  wherein the permanent magnet comprises a material having low electrical conductivity.  
     
     
         6 . The pump according to  claim 5  wherein the permanent magnet is a polymer bonded magnet.  
     
     
         7 . The pump according to  claim 6  wherein the rotor comprises a reinforcing sleeve for the polymer bonded magnet.  
     
     
         8 . The pump according to  claim 7  wherein the sleeve comprises a material having low electrical conductivity.  
     
     
         9 . The pump according to  claim 8  wherein the sleeve comprises a carbon reinforced plastics material.  
     
     
         10 . The pump according to  claim 4  wherein the rotor further comprises a sleeve comprising an electrically highly conductive material.  
     
     
         11 . (canceled)  
     
     
         12 . The pump according to  claim 1  wherein at least one of the plurality of teeth has a concave radially innermost surface and a projection projecting radially outwardly with respect to a corresponding one of the radially innermost surfaces.  
     
     
         13 . The pump according to  claim 12;  wherein plurality of yoke members have side surfaces disposed in abutting relationship so that a plurality of recesses are formed between the side surfaces.  
     
     
         14 . The pump according to  claim 13  wherein each of the plurality of yoke members comprises a first annular part having a side surface and a second annular part having a side surface wherein the recesses for the projections Beware defined by at least one of the side surfaces of the first annular part and the second annular part.  
     
     
         15 . The pump according to  claim 12  further comprising a motor shaft; and wherein the substantially circular passage defines an inside diameter of the stator, the rotor has an outside diameter and defines a through hole by which the rotor is mounted on the motor shaft, the through hole defines an inside diameter of the rotor and wherein the ratio of the outside diameter of a portion of the motor shaft on which the rotor is mounted to the inside diameter of the stator is less than or substantially equal to 2:3.  
     
     
         16 . The pump according to  claim 15  wherein the rotor outside diameter is less than the stator inside diameter and wherein the inside diameter of the rotor is substantially equal to the outside diameter of the portion of the motor shaft on which the rotor is mounted.  
     
     
         17 . The pump according to  claim 12  wherein the substantially circular passage defines an inside diameter of the stator, the rotor has an outside diameter and defines a through hole by which the rotor is mounted on a motor shaft and the through hole defines an inside diameter of the rotor, wherein the ratio of the inside diameter of the rotor and to the outside diameter of the rotor is less than or equal to 2:3.  
     
     
         18 . The pump according to  claim 1;  wherein the electric motor has speed from 20,000 to 100,000 rpm.  
     
     
         19 . The pump according to  claim 1  wherein at least one of the plurality of teeth has a concave radially innermost surface and a projection projecting radially outwardly with respect to a corresponding one of radially innermost surfaces, and wherein the radially innermost surfaces are arranged to form a substantially circular passage and wherein the yoke is adapted to have recesses for receiving the projections.