| 摘要 |
A spiral groove flow passage with a clockwise spiral direction and a spiral groove flow passage with a counterclockwise spiral direction are provided inside a spindle. When the spindle is accelerated to rotate in the forward rotation direction, a pressure in the direction of causing a reverse flow of a coolant is applied to the left-hand spiral groove flow passage by the axial-flow pumping action, but a pressure in the forward direction is applied to the right-hand spiral groove flow passage by the same axial-flow pumping action to cancel out the pressure causing the reverse flow described above. |
