| 摘要 |
PROBLEM TO BE SOLVED: To provide a structure which can be produced at a low cost without requiring any highly precise part and surely secures a sealing properly. SOLUTION: A driving shaft 24 revolves around a rotation shaftαof a pulley 13 according to the rotation of a pulley 13. According to this revolution, an impeller 4a freely rotationally supported to the driving shaft 24 is rotated in the inside of a water jacket 12. A bellows 23 is arranged between the outer circumferential face of the driving shaft 24 and the inner circumferential face of a casing 8, and water-tightness between both of the circumferential faces is maintained.
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