Rate shaping control valve for fuel injection nozzle

A fuel injector nozzle assembly comprising:

• a housing defining a blind bore and at least one injection orifice at a bottom portion of the blind bore and also defining a fuel injection passage therein providing fluid communication between the bottom portion of the blind bore and a source of pressurized fuel;
• a primary check slidably disposed in the blind bore, said primary check movable between first and second positions wherein said primary check in the first position blocks the at least one injection orifice;
• a primary check spring disposed between the primary check and the housing biasing the primary check toward the first position wherein pressurized fuel at a first valve opening pressure causes the primary check to lift from the bottom portion to permit the fuel to flow through the at least one injection orifice;
• a secondary check slidably disposed in the fuel injection passage against a seat therein on a source side thereof in a first position and defining a pilot orifice therethrough restricting fuel flow from the source of pressurized fuel to the primary check in the first position;
• a secondary check spring functionally disposed between the secondary check and the housing biasing the secondary check toward the first position wherein pressurized fuel from the source of pressurized fuel at a second valve opening pressure greater than the first valve opening pressure lifts the secondary check from the seat to permit substantially unrestricted fuel flow from the source of pressurized fuel to the primary check;
• and
• a back flow restriction in the fuel injection passage (inhibits) inhibiting flow therethrough from the primary check to the source of pressurized fuel.