TWO-STAGE CENTRIFUGAL PUMP

To provide a two-stage centrifugal pump that can prevent pump efficiency from being decreased by a collision between a main flow of liquid to be sucked into a first-stage impeller and a circulating flow.SOLUTION: A two-stage centrifugal pump 1 is constituted so as to attach first and second impellers 4 and 5 to a rotor shaft 3 to be rotated and driven by a motor part (driving source) M, discharge liquid pressurized by the rotation of the impellers 4 and 5, to the outside of a pump case 2, circulate a portion of the liquid discharged from the second impeller 5, through sliding bearings 7 and 8 of the rotor shaft 3, and return it as a circulating flow to the suction side of the first impeller 4, and is provided with a canopy-like guide protrusion (guide means) 24a for guiding the circulating flow of the liquid to a suction port 4a of the first impeller 4 so as to avoid a collision with a main flow of the liquid to be sucked into the first impeller 4.SELECTED DRAWING: Figure 2 【課題】初段のインペラに吸入され液体の主流と循環流との衝突によるポンプ効率の低下を防ぐことができる２段遠心ポンプを提供すること。【解決手段】モータ部（駆動源）Ｍによって回転駆動されるロータ軸３に第１及び第２インペラ４，５を取り付け、該インペラ４，５の回転によって昇圧された液体をポンプケース２外へと吐出するとともに、第２インペラ５から吐出される液体の一部をロータ軸３の滑り軸受７，８に循環させてこれを第１インペラ４の吸入側に循環流として戻すよう構成された２段遠心ポンプ１において、前記液体の循環流を第１インペラ４に吸引される液体の主流との衝突を避けて第１インペラ４の吸入口４ａへと導く庇状のガイド突起（ガイド手段）２４ａを設ける。【選択図】図２