Vacuum pump

Abstract

There is provided a vacuum pump capable of preventing foreign materials from flowing into a gap between rotors or the like and obtaining low ultimate pressure. The vacuum pump includes two rotating shafts formed extending in a first axial direction, a rotor casing, rotors, and a shielding portion. The rotor casing includes a rotor chamber disposed along the two rotating shafts, a suction port communicating with the rotor chamber, and an exhaust port communicating with the rotor chamber. The rotors are mounted on the two rotating shafts and disposed in the rotor chamber. The shielding portion is configured to prevent a gas sucked from the suction port into the rotor chamber from directly flowing into a gap between the rotors and is disposed between the suction port and inside the rotor chamber.

What is claimed is: 
     
         1 . A vacuum pump comprising:
 two rotating shafts formed extending in a first axial direction;   a rotor casing including a rotor chamber disposed along the two rotating shafts, a suction port communicating with the rotor chamber, and an exhaust port communicating with the rotor chamber;   rotors mounted on the two rotating shafts and disposed in the rotor chamber; and   a shielding portion configured to prevent a gas sucked from the suction port into the rotor chamber from directly flowing into a gap between the rotors and disposed between the suction port and inside the rotor chamber.   
     
     
         2 . The vacuum pump according to  claim 1 , wherein
 the rotors are roots type rotors or claw type rotors.   
     
     
         3 . The vacuum pump according to  claim 1 , wherein
 when viewed from the suction port toward inside the rotor chamber, the shielding portion is disposed in front of a gap between the rotors.   
     
     
         4 . The vacuum pump according to  claim 1 , wherein
 the shielding portion is disposed upstream of the rotors and is disposed between the two rotating shafts when viewed from the suction port toward inside the rotor chamber.   
     
     
         5 . The vacuum pump according to  claim 1 , wherein
 the shielding portion has a tapered shape narrow on an upstream side and wide on a downstream side.   
     
     
         6 . The vacuum pump according to  claim 1 , wherein
 the shielding portion has a curved surface shape protruding toward upstream.   
     
     
         7 . The vacuum pump according to  claim 1 , wherein
 the rotor chamber comprises multistage rotor chambers connected to each other through a gas flow path,   the rotors comprise multistage rotors, each disposed in each of the multistage rotor chambers, and   the shielding portion is disposed between the suction port and inside a first stage rotor chamber of the multistage rotor chambers.   
     
     
         8 . The vacuum pump according to  claim 7 , further comprising
 a foreign material capture unit having at least one of a trap and a filter disposed in the gas flow path connecting between stages of the multistage rotor chambers.   
     
     
         9 . The vacuum pump according to  claim 8 , wherein
 the foreign material capture unit is disposed in the gas flow path connecting between the first stage rotor chamber and a next stage rotor chamber of the multistage rotor chambers.   
     
     
         10 . The vacuum pump according to  claim 8 , wherein
 the gap between the rotor casing and the multistage rotors or the gap between the multistage rotors in each of the multistage rotor chambers downstream of the foreign material capture unit is formed smaller than the gap therebetween upstream thereof.   
     
     
         11 . The vacuum pump according to  claim 8 , further comprising
 a pressure sensor disposed in the gas flow path upstream of the foreign material capture unit for detecting a pressure.   
     
     
         12 . The vacuum pump according to  claim 8 , wherein
 the foreign material capture unit comprises a reticulated or porous filter.   
     
     
         13 . The vacuum pump according to  claim 1 , wherein
 the suction port is connected to a chamber where a gas containing non-sublimated foreign materials occurs.