Fuel injector valve needle lift control arrangement

An arrangement for controlling the lift of a valve needle in fuel injectors of direct injection internal combustion engines, said arrangement comprising:

• a hollow housing having a discharge end and an end face remote from said discharge end, said valve needle being axially displaceably supported in the discharge end of said housing for movement between a first seated position and a second unseated position, said housing having fuel inlet means operatively connected to said valve needle for supply fuel thereto, control medium inlet means for supplying control medium to said end face, and outlet means for communicating the hollow interior of said housing with the outside;
• a sleeve axially displaceably arranged within the hollow interior of said housing, said sleeve being open towards said discharge end and closed at said end remote from said discharge end for receiving control medium between said closed end of said sleeve and said end face of said housing, said sleeve having at least one opening for communicating the interior of said sleeve with said outlet means;
• piston means axially displaceably arranged within the hollow interior of said housing at the open end portion of said sleeve for closing said at least one opening, said piston means being operatively connected with said valve needle;
• at least one spring means operatively arranged between said sleeve and said piston for resiliently acting upon said valve needle, the control of the lift of said valve needle being substantially independent of spring characteristic;
• a further spring means for resiliently retaining said sleeve in a position wherein said closed end of said sleeve contacts said housing end face;
• said piston means being axially movable within said sleeve and said piston means including an aperture open away from said valve needle for receiving therein a pertaining end of said at least one spring means;
• a control pin having a first end extending through said closed sleeve end, a second end extending within said sleeve towards said piston means, and a collar between said first end and said second end for the provision of first and second annular shoulders, said collar being in sealing contact within said control sleeve, said further spring means being in contact with said first annular shoulder, and said at least one spring means being in contact with said second annular shoulder.