Injector valve seat with recirculation trap

A fuel injector comprising a body having an inlet at which pressurized liquid fuel is delivered to the fuel injector, a nozzle from which the fuel injector injects fuel, passage means for conveying fuel from said inlet to said nozzle, said nozzle comprising an orifice through which fuel is injected from the nozzle, said passage means comprising a seating surface that is disposed upstream of said orifice proximate said orifice and that converges in the downstream direction to give at the narrowest convergence of said seating surface a diameter that is spaced upstream and radially outwardly of said orifice, an electromechanically actuated mechanism comprising a valve member that is operated to selectively seat on and unseat from said seating surface and thereby allow and disallow fuel to be injected through said orifice, said seating surface and said valve member being constructed to have a coaction that, when said valve member is unseated from said seating surface to define a lift opening between them, directs the fuel in the direction of the convergence of said seating surface, said orifice being disposed out of the direction of the convergence of said seating surface such that fuel that has already passed through said lift opening and is flowing in the direction of convergence of said seating surface is required to execute a bend that diverges from the direction of the convergence of said seating surface before it passes through said orifice resulting in the creation of a fuel recirculation zone, said recirculation zone being characterized by some of the fuel approaching said orifice being recirculated as an eddy before it reaches said orifice, said passage means being formed as an undercut in the region of said recirculation zone, said undercut being disposed between said seating surface and said orifice and comprising a frustoconically expanding portion followed by a circular groove in the direction of said orifice, wherein a substantial portion of the recirculation zone occupies said undercut, such that the recirculation zone is displaced in a direction out of the path of said bend, thereby reducing a tendency of reduced fuel flow through one portion of said orifice in comparison to fuel flow through another portion of said orifice as a result of said eddy, whereby the flow through said one portion of said orifice more closely approaches the flow through said another portion of said orifice.