1. Field of Invention
The present invention relates to fuel injection valves for use in internal combustion engines.
2. Description of Related Art
Various types of fuel injection valves have been hitherto proposed and put into practical use particularly in the field of automotive internal combustion engines. One of them is disclosed in Laid-open Japanese Patent Application (Tokkai) 2000-8990, which generally comprises a valve element arranged in a casing to move between open and close positions and an electromagnetic coil arranged to actuate the valve element to move between the open and close positions in accordance with energization/de-energization of the electromagnetic coil. Upon opening of the valve element, a pressurized fuel in a fuel passage of the casing is injected into a given space, such as a combustion chamber, air intake passage or the like, of the internal combustion engine.
However, due to inherent construction, the fuel injection valves of the type disclosed by the above-mentioned Japanese Application tend to fail to exhibit a satisfied dimensional stability of the valve element. That is, for producing the valve element, a press working is employed to shape a given portion of the valve element, which however tends to induce a deformation or swelling of the given portion to which the pressing force is actually applied. As is known, such deformation or swelling (viz., dimensional poorness) induces a non-smoothed movement of the valve element and thus tends to exhibit a poor responsiveness of the same upon energization/de-energization of the electromagnetic coil. If, for smoothing the movement, a finish machining working is additionally employed for finely shaping the valve element, productivity of the fuel injection valve is lowered and thus cost performance of the same becomes poor.