| 摘要 |
PROBLEM TO BE SOLVED: To prevent the lowering of the pump efficiency caused by pressure loss and bubble generation by providing a pressure groove communicating the outer circumference to the central part of a pump chamber traversing a seal region between a start part and an end part of respective circumferential grooves in both inside faces of the pump chamber. SOLUTION: A suction port 23 continuing to a start part 20a of a first circumferential groove 20 is provided in an outer housing and a discharge port 24 continuing to the end part of a second circumferential groove 21 is provided in the inner housing. A first and a second pressure groove 291, 292 traversing a first and a second seal region 251, 252 between the start parts 20a, 21a and end parts 20b, 21b of a first and a second circumferential groove 20, 21 in the radial direction of a pump impeller 5 and reaching an swelling chamber part 4a are provided in respective inside faces of the inner housing and outer housing. By this constitution, the lowering of the pump efficiency caused by pressure loss and bubble generation can be prevented.
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