It is known in the art relating to fuel injectors to use hermetic laser welded joints rather than large space consuming O-rings to reduce the overall diameter of the injector. During the fabrication or assembly of such injectors, it is known to axially move the coil assembly on the fuel inlet tube to a position allowing the non-magnetic shell and fuel inlet tube to be welded together. After welding, the coil is displaced axially to cover the laser-welded joint.
Such construction does provide a reduced size fuel injector. However, a coil having a stepped or larger inside diameter is required to be axially displaced and fitted over the welded joint. A stepped coil eliminates space required for windings and is expensive. A coil having a larger inside diameter has less space available for windings.
Furthermore, such injectors typically require a short engagement length of the non-magnetic shell which is welded to the fuel tube, to allow some control of the injector length as the coil must be moved axially along the fuel tube. This short engagement length of the non-magnetic shell results in the working gap (the gap between the end of the fuel tube and armature) being outside the high flux area of the coil.
There is a need to further reduce the overall injector package size, especially the injector length, and to get the working gap into the high flux area of the coil.