ROTARY MULTI-STAGE VACUUM PUMP

摘要

PROBLEM TO BE SOLVED: To invariably reduce power consumption even when a multi-stage vacuum pump is continuously operated at a specified revolving speed in the normally used vacuum region by determining the ratio of volumes of pump segments constituting the multi-stage vacuum pump based on a specific value. SOLUTION: The gas G11 sucked from the suction port 11 of a first pump segment of this multi-stage vacuum pump is compressed by a rotor 12 and flows into a cooler 16 from a discharge port 13 to be cooled. The gas flowing into the suction port 21 of a second pump segment is divided into the compressed gas G22 and the backflow cooled gas flowing back to the first pump segment, and the backflow cooled gas flows into the housing of the first pump segment from the inflow port of the backflow cooled gas through an outer peripheral gas passage and is compressed and discharged from a discharge port 13 with its temperature rise suppressed low. The above actions are conducted in sequence in individual pump segments. The ratio of volumes of pump segments constituting this n-stage vacuum pump is selected larger than the value of n/(n-1) in sequence from the final pump segment.