DIRECTLY ACTUATED INJECTION VALVE WITH A COMPOSITE NEEDLE

摘要

A directly actuated injection valve (100) comprises a hollow valve housing (102), a valve needle (114) disposed within the hollow interior, a needle spring (116), and a magnetostrictive (130) actuator assembly disposed in an annular space around a portion of the valve needle. A magnetic field actuates the magnetostrictive material to change its length to cause a corresponding movement of the valve needle (114) that actuates the valve. The valve needle is comprises of a plurality of portions. The portion (114a) of the needle that extends through the magnetostrictive actuator assembly is formed from a non-ferromagnetic material and the portion of the needle comprising the needle tip (114c), which contacts the valve seat (111), is formed from a different material that has higher through-hardness than that the non-ferromagnetic material. The portion of the needle formed from a non-ferromagnetic material prevents interference with the flux field that is directed through the magnetostrictive member. The use of a different material for the needle tip reduces the effects of wear and improves durability.