Vacuum pump

Abstract

A vacuum pump ( 1 ) includes: a rotor ( 30 ) provided with a rotor-side discharge function unit ( 32 ); a motor ( 36 ) that drives the rotor ( 30 ) to rotate with respect to a stator-side discharge function unit ( 22 ); and a cylindrical pump casing ( 2 ) made of a magnetic material, in which the rotor ( 30 ) and the stator-side discharge function unit ( 22 ) are disposed.

1 . A vacuum pump comprising:
 a rotor provided with a rotor-side discharge function unit;   a motor that drives the rotor to rotate with respect to a stator-side discharge function unit; and   a cylindrical pump casing made of a magnetic material, in which the rotor and the stator-side discharge function unit are disposed.   
     
     
         2 . A vacuum pump according to  claim 1 , wherein
 the rotor-side discharge function unit includes
 a plurality of stages consisting of rotor turbine blades disposed in an inner space of the pump casing, and 
 a cylindrical drag pump rotating portion provided at a downstream side of the stages consisting of rotor turbine blades outside the inner space of the pumping casing, and 
   the stator-side discharge function unit includes
 a plurality of stages consisting of stator turbine blades, and 
 a cylindrical drag pump fixing portion which is disposed so as to surround an outer circumferential surface of the drag pump rotating portion at a gap therefrom and which is made of a magnetic material. 
   
     
     
         3 . A vacuum pump according to  claim 1 , further comprising:
 a magnetic bearing unit that includes a thrust magnetic bearing that supports the rotor in an axial direction and a radial bearing that supports the rotor in a radial direction,   a pump base portion that is provided with the magnetic bearing unit and that is made of a non-magnetic material,   an axial sensor that detects a position in the axial direction of the rotor,   a radial sensor that detects a position in the radial direction of the rotor,   a first magnetic shield member that is made of a magnetic material and that is provided at an inlet of the pump casing to reduce entrance of external magnetic field into the pump via the inlet, and   a second magnetic shield member that is made of a magnetic material and that is provided at the pump base portion to reduce influence of external magnetic field on the magnetic bearing unit.   
     
     
         4 . A vacuum pump according to  claim 3 , wherein
 the second magnetic shield member constitutes a vacuum container in which at least the axial sensor is housed.   
     
     
         5 . A vacuum pump according to  claim 4 , further comprising:
 a third magnetic shield member made of a magnetic material that extends in the direction of from the second magnetic shield member to the pump casing so as to cover an outer circumferential surface of the pump base portion that is made of the non-magnetic material.   
     
     
         6 . A vacuum pump according to  claim 5 , wherein
 the second magnetic shield member and the third magnetic shield member are formed into a one body   
     
     
         7 . A vacuum pump according to  claim 3 , wherein
 the magnetic shield member includes a disc portion and a supporting beam that supports the disc portion at a center of the inlet.   
     
     
         8 . A vacuum pump according to  claim 7 , wherein
 the rotor includes a plurality of stages consisting of turbine blades as the rotor-side discharge function unit,   the disc portion has an outer diameter D, which is not smaller than an outer diameter Ds of the radial sensor and not larger than a diameter Dri of a circle that passes a joint of each of the turbine blades in a circumferential direction of the rotor.   
     
     
         9 . A vacuum pump according to  claim 1 , further comprising:
 a protective net that is fastened to the inlet of the pump casing with bolts to prevent foreign matter from entering the pump, the pump casing being formed of threaded through-holes for fastening with bolts.   
     
     
         10 . A vacuum pump according to  claim 3 , wherein
 the first magnetic shield member serves as the protective net that is provided at the inlet of the pump casing and prevents foreign matter from entering the pump.   
     
     
         11 . A vacuum pump according to  claim 1 , wherein
 the magnetic material includes a carbon steel or an alloy steel.   
     
     
         12 . A vacuum pump according to  claim 11 , wherein
 the pump casing is made of S45C as the carbon steel.   
     
     
         13 . A vacuum pump according to  claim 11 , wherein
 a surface of the magnetic material is subjected to anticorrosion treatment including N—P plating treatment.