Fuel pump having an impeller with axially balanced forces acting thereon

An improvement in a fuel pump for an internal combustion engine in which the fuel pump comprises an electric motor over which fuel is pumped to cool the motor, and a pump mechanism, constituted as a side-channel pump is driven by the electric motor to pump the fuel, said pump mechanism having a pump impeller provided with two opposite radial surfaces each provided with an annular ring of blades respectively cooperating with side channels provided in a pump wall, the ring of blades and one side channel constituting a first pump stage and the ring of blades and the other side channel constituting a second pump stage, and a connecting channel connecting an inlet region of the side channel of the second pump stage with a discharge region of the side channel of the first pump stage, said discharge region and said inlet region being arranged to substantially eliminate torsional moments acting on the radial surfaces of the impeller during a fuel pumping operation, said improvement comprising:

• a first flat region on the radial surface of said pump impeller in said first pump stage,
• a second flat region on the radial surface of said pump impeller in said second pump stage,
• first connection means for applying pressure of the fluid discharged from the second pump stage to said first flat region, and
• second connection means for applying pressure of the fluid discharged from the first pump stage to said second flat region,
• whereby a net axial force applied to the first and second flat regions of said pump impeller by the respective pressures of the fluid in the first and second stages substantially counterbalance a force produced on the pump impeller by the pressure of the fluid discharged from the first pump stage acting in the direction of the first pump stage.