US Patent 7086614 Fuel injector

A fuel injector is described for fuel injection systems in internal combustion engines that includes a magnet coil, an armature that is acted upon in a closing direction by a restoring spring, and a valve needle that is non-positively engaged with armature for actuating a valve closing body, which together with a valve seat surface forms a sealing seat, and armature with an inlet-side armature surface striking internal pole. A choke point is provided on inlet-side armature surface, and is formed by an annular, stepped prominence on inlet-side armature surface.