Vacuum pump

Abstract

A vacuum pump including a centrifugal compressor stage on the side of a suction opening and a circumferential flow compressor on the side of an exhaust opening. The centrifugal compressor pump works as a Siegbahn pump at a steady state, and works as a centrifugal compressor under a transient condition at the initial stage of the pump operation, thus obtaining a high pumping speed under the transient condition.

What is claimed is: 
     
       1. A vacuum pump comprising: a housing including suction and exhaust openings, a rotating shaft rotatably supported in said housing, a plurality of fixed members attached to an inner wall of said housing, and a plurality of rotating members attached to said rotating shaft, said fixed members and said rotating members being disposed alternately so as to form pump stages in which a centrifugal compressor stage is formed on a side of said suction opening and a circumferential flow pump stage is formed on a side of said exhaust opening, said rotating member of said centrifugal compressor stage including open-form impellers having a plurality of backward vanes, and wherein said fixed member of said centrifugal compressor stage includes a fixed disc plate with a plurality of vanes disposed so as to face a reverse side of said impeller and inwardly directed relative to the direction of rotation at an outside diametral portion of said fixed member. 
     
     
       2. A vacuum pump comprising: a housing including suction and exhaust openings, a rotating shaft rotatably supported in said housing, a plurality of fixed member attached to an inner wall of said housing, and a plurality of rotating members attached to said rotating shaft, said fixed members and said rotating members being disposed alternately so as to form pump stages in which a centrifugal compressor stage is formed on a side of said suction opening and a circumferential flow pump stage is formed on a side of said exhaust opening, said rotating member of said centrifugal compressor stage including open-form impellers having a plurality of backward vanes, and wherein a diameter of said circumferential flow compressor stage on a side of said exhaust opening is smaller than a diameter thereof on a side of said suction opening. 
     
     
       3. A vacuum pump according to claim 2, comprising: a housing including suction and exhaust openings, a rotating shaft rotatably supported in said housing, a plurality of fixed member attached to an inner wall of said housing, and a plurality of rotating members attached to said rotating /shaft, said fixed members and said rotating members being disposed alternately so as to form pump stages in which a centrifugal compressor stage is formed on a side of said suction opening and a circumferential flow pump stage is formed on a side of said exhaust opening, said rotating member of said centrifugal compressor stage including open-form impellers having a plurality of backward vanes, and wherein a diameter of said circumferential flow compressor stage on a side of said exhaust opening is smaller than a diameter thereof on a side of said suction opening. .Iadd. 
     
     
       4.  A vacuum pump comprising: a housing including a suction and exhaust openings, a rotating shaft rotatably supported in said housing, a plurality of fixed members attached to an inner wall of said housing, and a plurality of rotating members attached to said rotating shaft, said fixed members and said rotating members being disposed alternately so as to form pump stages in which a centrifugal compressor stage is formed on a side of said suction opening and a circumferential pump stage is formed in a side of said exhaust opening, said rotating member of said centrifugal compressor stage including impellers having a plurality of backward vanes, and wherein said fixed member of said centrifugal compressor stage includes the fixed disc plate with a plurality of vanes disposed so as to face the reverse side of said impeller and inwardly directed relative to the direction of rotation of an outside diametral portion of said fixed member. .Iaddend. .Iadd.5. A vacuum pump comprising: a housing including a suction and exhaust openings, a rotating shaft rotatably supported in said housing, a plurality of fixed members attached to an inner wall of said housing, and a plurality of rotating members attached to said rotating shaft, said fixed members and said rotating members being disposed alternately so as to form pump stages in which a centrifugal compressor stage is formed on a side of said suction opening and a circumferential flow pump stage is formed in a side of said exhaust opening, said rotating member of said centrifugal compressor stage including impellers having a plurality of backward vanes, and wherein a diameter of said circumferential flow compressor stage on a side of said exhaust opening is smaller than a diameter thereof on a side of said suction opening. .Iaddend. .Iadd.6. A vacuum pump according to claim 5, comprising a housing including suction and exhaust openings, a rotating shaft rotatably supported in said housing, a plurality of fixed members attached to an inner wall of said housing, and a plurality of rotating members attached to said rotating shaft, said fixed members and said rotating members being disposed alternately so as to form pump stages in which a centrifugal compressor stage is formed on a side of said suction opening and a circumferential flow pump stage is formed on a side of said exhaust opening, said rotating member of said centrifugal compressor stage including impellers having a plurality of backward vanes, and wherein a diameter of said circumferential flow compressor stage on a side of said exhaust opening is smaller than a diameter thereof on a side of said 
     
     
        suction opening. .Iaddend. .Iadd.7.  A vacuum pump having a housing including a suction opening and an exhaust opening and a pump stage disposed in said housing, said pump stage comprising: a centrifugal compressor stage means disposed on a side of the suction opening in said housing for obtaining a high compression ratio in a molecular flow and an intermediate flow region and then generating a compressive operation in a viscous flow region, a circumferential flow pump stage means disposed on a side of said exhaust opening in said housing for obtaining a high compression ratio in the viscous flow region, and a rotating shaft means disposed between said centrifugal compressor stage means and circumferential flow pump stage means. .Iaddend. .Iadd.8. A vacuum pump according to claim 7, wherein the centrifugal compressor stage means includes impeller means attached to the rotating shaft means, a fixed disc plate means attached to an inner wall of the housing and including a plurality of vanes inwardly directed relative to said direction of rotation and disposed on a reverse side of said impeller means. .Iaddend. .Iadd.9. A vacuum pump according to claim 8, wherein said impeller means and said fixed disc plate means are alternately arranged.   
     
     
        .Iaddend. .Iadd.10.  A vacuum pump according to claim 9 wherein said impeller means includes a plurality of backward vanes. .Iaddend.