PURPOSE: To improve the compression ratio of the final compression pump stage and obtain the small-sized vacuum pump having high faculty by exhausting the gas in the vacuum pump by the ejector effect of the jetted gas by installing a gas injection port midway in an exhaust passage and an exhaust pipe having a throttle.
CONSTITUTION: A rotary shaft 1 is supported by a bearing 7 in a housing 2 having a suction port 2A and an exhaust port 2B. In the housing 2, a centrifugal compression pump stage 5 and a circumferential flow compression pump stage 6 are connected in succession from the suction port 2A side to the exhaust port 2B side. In this case, in the midway of an exhaust passage 2C communicating to the exhaust port 2B, a nozzle 12 for jetting the high pressure gas supplied from a high pressure gas inlet 11 towards the exhaust port 2B is installed. The gas jetted from the injection port 12A flows into an exhaust pipe 2D having a throttle, and the vicinity of the nozzle 12 is allowed to act as ejector type vacuum pump stage is increased.
NAGAOKA TAKASHI
TANIYAMA MINORU
MASE MASAHIRO
TSURU SEIJI
