ELECTRICALLY-DRIVEN SUPERCHARGER

PROBLEM TO BE SOLVED: To raise a frequency of axial resonance by enhancing the rigidity of a rotating body while suppressing an increase of a mass of the rotating body without largely changing a current specification, in a supercharger.SOLUTION: In a supercharger 1, a step 18 is formed by making a portion at a one-end side of a shaft 4 small in diameter rather than the other portion, and making the one-end side as a one-end side small diameter part 4a, and a position of a rotating vane 3 with respect to the shaft 4 in an axial direction is decided by making the step 18 abut on an abutment part 19 which is arranged in a hole 7. Furthermore, positions of the step 18 and the abutment part 19 are set on the one-end side in the axial direction rather than a center of gravity G with respect to a total sum of a mass of the portion on the one-end side in the axial direction rather than an opening 20 of the hole 7 and a mass of the rotating vane 3 out of shaft 4. By this constitution, since the rotating vane 3 can be supported by the other end side large-diameter part 4b by making the other end side large-diameter part 4b intrude into the hole 7, the rigidity of a rotating body 16 is enhanced, and a frequency of an axial resonance can be raised.SELECTED DRAWING: Figure 2 【課題】過給機において、回転体の質量増加を抑えつつ、かつ、現状の仕様を大幅に変更することなく、回転体の剛性を高めて軸共振の周波数を高める。【解決手段】過給機１によれば、シャフト４の一端側の部分を他の部分よりも小径にして一端側小径部４ａにすることで段１８を設けるとともに、孔７内に設けた突き当て部１９に段１８を突き当てることで、シャフト４に対する回転翼３の軸方向の位置を決める。さらに、シャフト４の内、孔７の開口２０よりも軸方向の一端側の部分の質量と回転翼３の質量との合計に対する重心Ｇよりも、段１８および突き当て部１９の位置を、軸方向の一端側に設定する。これにより、孔７内に、他端側大径部４ｂを入り込ませて、回転翼３を他端側大径部４ｂで支持することができるので、回転体１６の剛性を高めて軸共振の周波数を高めることができる。【選択図】図２