To enhance a vapor lock preventing function in a two-stage electrically driven fuel pump, by specifying a ratio between the cross sectional area of the outlet hole a first pump chamber and the cross sectional area of the channel of the first pump chamber, and also communicating the channel of the first pump chamber with the outside through a vapor extracting hole.
In an in-tank type electrically driven fuel pump, a Westco type pump 4 driven by the shaft 3 of an electric motor 2 is arranged, and is composed as a two- state pump equipped with first and second pump chambers 15, 16. In this case, a ratio between the cross sectional area of the outlet hole of the first pump chamber 15 and the cross sectional area of the channel of the first pump chamber 15 is set not less than 0.5 nor more than 1.4, and set to a value smaller than a ratio between the cross sectional area of the outlet hole of the second pump chamber 16 and the cross sectional area of the channel of the second pump chamber 16, and the channel of the first pump chamber 15 is communicated with the outside through a vapor extracting hole. The impellers of the first and second pump chambers 15, 16 are made to have the same diameter, and preferably set in a range of not less than 25mm nor more than 50mm.
MINE KOICHI
KIKUTA HIKARI
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