Screw vacuum pump

Abstract

A screw vacuum pump includes a male rotor, a female rotor, a stator, and a drive motor/motors. A screw gear portion of the male rotor, a screw gear portion of the female rotor, and the stator cooperatively form a gas working chamber. The stator has an inlet port and an outlet port. At least one of the male rotor and the female rotor has a rotor hollow portion which is opened on at least one end face side in a rotation-axis longitudinal direction of the male rotor and/or the female rotor. The drive motor is at least partially received in the rotor hollow portion.

1 . A screw vacuum pump comprising a male rotor and a female rotor respectively having, on their outer peripheral sides, screw gear portions engaging each other, a stator receiving therein the male rotor and the female rotor, and a drive motor/motors for rotating the male rotor and the female rotor,
 the screw gear portion of the male rotor, the screw gear portion of the female rotor, and the stator cooperatively form a gas working chamber,   the stator has an inlet port and an outlet port adapted to communicate with one end and the other end of the gas working chamber,   at least one of the male rotor and the female rotor has a rotor hollow portion which is opened on at least one end face side of the male rotor and/or the female rotor in a rotation-axis longitudinal direction, and   the drive motor is at least partially received in the rotor hollow portion.   
     
     
         2 . The screw vacuum pump according to  claim 1 , wherein
 the male rotor and the female rotor respectively have the rotor hollow portions,   the drive motors are provided in the number of two, and   the respective drive motors are at least partially received in the rotor hollow portions of the male rotor and the female rotor, respectively.   
     
     
         3 . The screw vacuum pump according to  claim 1 , wherein
 the screw vacuum pump further comprises rotation shafts at least partially received in the rotor hollow portion/portions and fixed to at least one of the male rotor and the female rotor and at least two bearings for each of the rotation shafts, and   wherein the drive motor is disposed between the bearings.   
     
     
         4 . The screw vacuum pump according to  claim 1 , wherein the stator comprises a stator body portion receiving therein the male rotor and the female rotor and a support portion partially received in the rotor hollow portion/portions and supporting the drive motor/motors and/or the bearings. 
     
     
         5 . The screw vacuum pump according to  claim 1 , wherein each of the screw gear portions of the male rotor and the female rotor comprises an unequal lead unequal inclination angle screw portion disposed on the inlet port side and an equal lead screw portion with one lead or a plurality of leads which is continuous with the unequal lead unequal inclination angle screw portion. 
     
     
         6 . The screw vacuum pump according to  claim 1 , wherein each of the screw gear portions of the male rotor and the female rotor comprises a first equal lead screw portion disposed on the inlet port side, an unequal lead unequal inclination angle screw portion continuous with the first equal lead screw portion, and a second equal lead screw portion with one lead or a plurality of leads which is continuous with the unequal lead unequal inclination angle screw portion. 
     
     
         7 . The screw vacuum pump according to  claim 1 , wherein engagement of the male rotor and the female rotor is located outside gear engagement pitch circles determined by a distance between a rotation axis of the male rotor and a rotation axis of the female rotor and the numbers of teeth of the male rotor and the female rotor. 
     
     
         8 . The screw vacuum pump according to  claim 1 , wherein
 the screw vacuum pump further comprises rotation shafts fixed to at least one of the male rotor and the female rotor and oil supply unit for supplying lubricating oil, and   wherein the oil supply means unit comprises an oil storage portion storing the lubricating oil, push-up heads fixed to the rotation shafts for pushing up the lubricating oil from the oil storage portion by the use of rotation of the rotation shafts, and oil flow paths for supplying the lubricating oil, pushed up by the push-up heads, to predetermined portions.   
     
     
         9 . The screw vacuum pump according to  claim 8 , wherein the screw vacuum pump further comprises a cooling device for cooling the lubricating oil.