| 摘要 |
PURPOSE:To prevent cavitation, by forming a length, in which a normal direction suction port side radius of a minor circle part is subtracted from a normal direction suction port side radius of a major circle part, larger than the length, in which a reverse direction suction port side radius of the minor circle part is subtracted from a reverse direction suction port side radius of the major circle part, in a cam ring. CONSTITUTION:A cam ring 22 forms a cam surface 33 which comprises a major circle part 31 and a minor circle part 32. A length, in which a radius in the side of normal direction suction port 38 in the minor circle part 32 is subtracted from a radius R1 in the side of the normal direction suction port 38 in the major circle part 31, is formed larger than the length in which a radius in the side of a reverse direction suction port 39 in the minor circle part 32 is subtracted from a radius R2 in the side of the reverse direction suction port 39 in the major circle part 31. Accordingly, unreasonable pumping action of a suction chamber 40 is not generated in a delivery chamber 36 to which the reverse direction suction port 39 is opened, and no cavitation is generated in the suction chamber 40.
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