| 摘要 |
PURPOSE:To avoid generation of a vapor lock by providing a gas ventilation passage having a step and directed from a passage bottom portion toward the inside in a radial direction and a through hole having a cross sectional area larger than that of the gas ventilation passage and communicating to the outside of the casing assembly in the vicinity of an impeller on the inner circumference of a passage of a casing assembly. CONSTITUTION:When an impeller 4 is rotated and driven clockwise liquid fuel is sucked from a suction port 8 in a pump passage 7 and discharged from a discharge port 9. In this time, air bubbles generated at a contact face between the blade portion 5 of the impeller 4 and the liquid are collected and stored in the vicinity of an impeller on the inner circumference of the pump passage 7 and flow in the same direction as that of the rotation of the impeller together with the liquid and when they approach a gas ventilation passage 11 which has a step 10 from a passage bottom portion 10 and extends in the direction matching that of a swirl flow generated by the impeller, the air bubbles containing no liquid are forcibly guided to flow in the passage 11 due to static pressure in the pump passage and dynamic pressure caused by the swirl flow 13 so as to communicate with the passage 11, and discharged outside a casing assembly 1 via a through hole 10, having a cross sectional area large than that of the passage without any resistance. Consequently, the lowering of pump capacity can be avoided.
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