To use an injection-molded impeller as it is without grinding it.
This impeller 7 is provided with a plurality of vane grooves 12 on the outer periphery of a synthetic resin-made disc-shaped member 8 to be rotated by a motor, and it is rotatably housed in an approximately disc- shaped space 6 formed between a pump casing 4 and a pump cover 5. Disk- shaped recessed parts 14 are formed on both side surfaces 10, 11 of the disc- shaped member 8. The ratio (L/2t) of the sum (t1+t2=2t) of a clearance (t1) between one side surface 10 and the pump casing 4 and a clearance (t2) between the other side surface 11 and the pump cover 5 to the size (L=RO-H-R1) obtained by subtracting the radial groove length (H) of the impeller groove 12 and the radial size (R1) of the recessed part 14 from the radial size (RO) of the disc-shaped member 8 is set to 66≤(L/2t).
TATEZAWA TADAYOSHI
TAKEUCHI YOICHI
