Vacuum pump

Abstract

A vacuum pump, particularly a turbomolecular pump or multi-inlet pump, comprises a rotor shaft ( 12 ) carrying at least one rotor means ( 14 ). The rotor shaft ( 12 ) is supported on the pressure side by a bearing assembly ( 56 ) and on the suction-side by a further bearing assembly ( 30 ). According to the invention, the suction-side bearing assembly ( 30 ) comprises an electromagnetic bearing ( 32,34 ). Further according to the invention, the pressure-side bearing assembly ( 56 ) comprises a ball bearing ( 58 ) so that the rotor shaft ( 12 ) can be given the largest possible length. The rolling bearing ( 58 ) is preferably biased by the electromagnetic bearing ( 32,34 ).

1 . A vacuum pump, particularly a turbomolecular pump or multi-inlet turbomolecular pump, said vacuum pump comprising:
 a rotor shaft carrying at least one rotor means, and   a pressure-side bearing assembly and a suction-side bearing assembly supporting said rotor shaft,   said suction-side bearing assembly comprising an electromagnetic bearing which radially supports the rotor shaft, and said pressure-side bearing assembly comprising a rolling bearing which axially and radially supports said rotor shaft.   
     
     
         2 . The vacuum pump according to  claim 1 , wherein the suction-side bearing assembly serves exclusively for radial support. 
     
     
         3 . The vacuum pump according to  claim 1 , further including a biasing assembly which axially biases said rolling bearing. 
     
     
         4 . The vacuum pump according to  claim 3 , wherein said biasing assembly is formed by the suction-side bearing assembly. 
     
     
         5 . The vacuum pump according to  claim 3 , wherein said biasing assembly is formed by an electric motor which drives the rotor shaft. 
     
     
         6 . The vacuum pump according to  claim 3 , wherein said biasing assembly is formed by a separate magnet. 
     
     
         7 . The vacuum pump according to  claim 1 , wherein at least one of the suction-side bearing assembly and the pressure-side bearing assembly is arranged at an end of the rotor shaft. 
     
     
         8 . The vacuum pump according to  claim 1 , wherein all rotors are arranged between said bearing assemblies. 
     
     
         9 . The vacuum pump according to  claim 1 , wherein the rotor shaft between the two bearing assemblies has a length of at least 170 mm, with a rotor diameter of 100 to 140 mm. 
     
     
         10 . The vacuum pump according to  claim 1 , wherein the rotor shaft has a length between the two bearing assemblies that is larger than or equal to a diameter of the at least one rotor. 
     
     
         11 . The vacuum pump according to  claim 1 , wherein at least the suction side end of the rotor shaft has a reduced diameter. 
     
     
         12 . The vacuum pump according to  claim 1 , wherein the suction-side bearing assembly is arranged within a cartridge closed on the suction side. 
     
     
         13 . The vacuum pump according to  claim 1 , wherein the suction-side bearing assembly is arranged in a high vacuum region in which the pressure is less than 10 −5  mbar. 
     
     
         14 . The vacuum pump according to  claim 6 , wherein the separate magnet is a permanent magnet arranged in the region of the rolling bearing. 
     
     
         15 . The vacuum pump according to  claim 9 , wherein the rotor shaft has a length of at least 220 mm. 
     
     
         16 . The vacuum pump according to  claim 9 , wherein the rotor diameter is about 130 mm. 
     
     
         17 . The vacuum pump according to  claim 11 , wherein the suction side end of the rotor shaft is smaller than or equal to 0.66 times a root of a rotor diameter of the at least one rotor. 
     
     
         18 . The vacuum pump according to  claim 17 , wherein the suction side end of the rotor shaft has a reduced diameter smaller than 6 mm. 
     
     
         19 . The vacuum pump according to  claim 1 , wherein the suction-side bearing assembly is arranged in a high vacuum region in which the pressure is less than 10 −10  mbar. 
     
     
         20 . A turbomolecular vacuum pump comprising:
 a housing having a suction inlet adjacent a suction-side and an outlet adjacent a pressure-side;   a rotor shaft;   at least one rotor supported by the rotor shaft and at least one stator supported by the housing;   an electromagnetic bearing assembly supporting a suction-end of the rotor shaft in an interior of the housing and adjacent a suction-side of the housing, the suction-side bearing assembly including:
 a magnetic bearing element affixed to and rotating with the rotor shaft, 
 a coil mounted into the housing, and 
 an isolation structure which vacuum isolates the coil from the interior of the housing; and 
   a rolling bearing supporting a pressure-end of the rotor shaft in the interior of the housing adjacent the pressure-side of the housing.