Compressed natural gas injector having improved low noise valve needle

Abstract

An electromagnetically operable fuel injector for a fuel injection system of an internal combustion engine, the injector having a generally longitudinal axis, and including a ferromagnetic core, a magnetic coil at least partially surrounding the ferromagnetic core, and an armature magnetically coupled to the magnetic coil and being movably responsive to the magnetic coil. The armature is adapted to actuate a valve closing element interactive with a fixed valve seat and being movable away from the fixed valve seat when the magnetic coil is excited. The armature has a generally cylindrical shape and a generally central opening defining a through-passage for reception of fuel from a fuel inlet connector positioned adjacent thereto. A valve-closing element is attached to the armature and is positioned to be selectively moved toward and away from the fixed valve seat. The valve closing element is in the form of an elongated valve needle having a generally central shaft portion and a generally cylindrical end portion, the generally cylindrical end portion having a diameter greater than the generally central shaft portion and a sealing end surface having a spherical shape. Although gaseous fuels such as compressed natural gas are primarily contemplated, the invention is applicable for use with liquid fuels.