Patent ID: 6360727
Filing Date: 2002-03-26
Classification: F02M

Abstract:
In a diesel injection system, a pump and a pump chamber, said pump pressurizing fuel in the pump chamber on each injection cycle, an injection nozzle and an associated nozzle valve, said valve having a given opening pressure and a given lower closing pressure, said injection nozzle having nozzle orifices, said injection system having an injection-pressure side and a fuel supply/drain side, a variable-volume flow-subtraction chamber ported to said injection-pressure side of said system, a flow-subtraction piston loaded by a spring, said piston being slidably associated with said flow-subtraction chamber and, against the bias of said spring, being liftable, by pressurized fuel coming from said injection-pressure side of said system, from a closed, minimum-volume position through intermediate positions to a maximum-volume position at which further movement away from said minimum-volume position is stopped, a flow-subtraction control orifice between said injection-pressure side of said system and said flow-subtraction chamber, said control orifice maintaining, as between flow through said injection nozzle orifices and flow through said flow-subtraction control orifice, predetermined proportioning of flow of pressurized fluid passing from said injection-pressure side of said system prior to said flow-subtraction piston stopping at its said maximum-volume position in each injection cycle, said proportioning being the same as the proportion between the combined cross-sectional area of said nozzle orifices and the cross sectional area of said control orifice, said closed, minimum-volume position of said flow-subtraction piston being characterized by a relatively high opening-pressure requirement whereby during each feed stroke of the pump subtractive flow through said flow-subtraction orifice is delayed until said relatively high opening-pressure requirement is met and said piston lifts from its closed, minimum-volume position, the force of said spring and the area of exposure of said piston to pressure of incoming fuel, at said minimum-volume position of said flow-subtraction piston, being such that said piston starts to lift from its said closed, minimum-volume position at or about the time said given opening pressure of said nozzle valve is reached, said intermediate positions of said flow-subtraction piston being open positions characterized by relatively lower translating-pressure requirements such that, after said opening-pressure requirement is met, then, throughout the travel of said piston to its said maximum-volume position, the rate of subtractive flow is limited by the cross-sectional area of said flow-subtraction control orifice such as to accomplish the aforesaid proportioning, the spring rate of said spring being sufficiently low and the diameter of said piston sufficiently large that, once subtractive flow commences through said flow-subtraction control orifice, said flow is never significantly limited by resistance from said spring at any time throughout travel of said piston to its said maximum-volume position, said flow-subtraction piston being loaded by said spring toward said minimum-volume position to return thereto upon reduction of pressure in said injection-pressure side of said system after injection terminates in each cycle, the cross-sectional area of said flow-subtraction control orifice being both compatible with the accomplishment of the aforesaid proportioning and sufficiently small that, as such piston lifts from said closed, minimum-volume position, pressure upstream of said orifice drops only minimally so that injection proceeds without interruption during the injection phase of each cycle of operation of said injector at various loads and operating speeds.