US Patent 7217084 Automotive fuel pump with pressure balanced impeller

A rotary fuel pump employs pressure balancing features on the non-vaned side of the impeller to provide localized application of fluid forces so that the impeller is more precisely balanced within the pumping chamber. A generally disc-shaped impeller body has an impeller with a body-side surface and a cover-side surface. The cover-side surface defines an impeller flow channel extending circumferentially around the impeller. The impeller includes a plurality of vanes positioned at least partially within the impeller flow channel. The body-side surface has a plurality of discontinuous undercut regions each coaxially aligned with at least a portion of the impeller flow channel. The impeller has a plurality of apertures wherein each aperture connects the impeller flow channel with a respective undercut region, whereby pressure forces against the impeller from the fuel are substantially balanced in the axial direction.