Multiple stage fuel pump

A multi-stage fuel pump comprising:

• a casing having a fuel intake formed on one side thereof and a fuel discharge port formed on the other side thereof;
• and
• a plurality of impellers provided within the casing, having a plurality of blades disposed on a circumferential surface in an outward direction of the circumferential surface and having blade chambers formed between the blades and penetrating through upper and lower surfaces of the impellers to allow fuel to be discharged and introduced to and from upper and lower sides of the blades, and formed in multiple stages,
• wherein a flow channel is formed such that fuel intaken through the fuel intake according to rotation of the impellers is discharged to the fuel discharge port through the blade chambers of the impellers, and
• the numbers of the blades of each of the impellers are different,
• wherein the casing comprises:
• an upper casing having an upper flow channel recess formed on a lower surface thereof and allowing fuel to flow therein and the fuel discharge port connected to the upper flow channel recess and allowing fuel to be discharged by penetrating through upper and lower surfaces thereof;
• an intermediate casing coupled to a lower side of the upper casing having an intermediate upper flow channel recess formed on an upper surface thereof and allowing fuel to flow therein and an intermediate lower flow channel recess formed on a lower surface thereof and allowing fuel to flow therein;
• and
• a lower casing coupled to a lower side of the intermediate casing and having a lower flow channel recess formed on an upper surface thereof and allowing fuel to flow therein and the fuel intake connected to the lower flow channel recess and allowing fuel to flow by penetrating through upper and lower surfaces thereof,
• wherein the impellers are provided in a space between the upper casing and the intermediate casing and a space between the intermediate casing and the lower casing, respectively,
• wherein an intake flow channel is formed in the intermediate casing such that a fuel inlet side and the fuel intake of another impeller are connected through a fuel inlet side of one impeller;
• and
• a discharge flow channel is formed in the upper casing and the intermediate casing such that each of fuel outlet sides of the impellers is connected to the fuel discharge port.