| 摘要 |
An impeller ( 1 ) according to the present invention has a disk-like main plate ( 10 ), a blade ( 20 ) joined to the main plate, and a side plate ( 30 ) having a suction port. A boss hole ( 12 ) is formed in a central portion of the main plate for attaching a boss which engages with a pump shaft to the boss hole. A step portion ( 14 ) is formed around the boss hole, which is formed in the main plate, by drawing.
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