Needle controlled fuel system with cyclic pressure generation

A unit fuel injector for receiving low pressure fuel from a fuel supply and injecting the fuel at a high pressure into a combustion chamber of an engine, comprising:

• an injector body containing an injector cavity, a fuel transfer circuit and an injection orifice formed in one end of said injector body;
• and
• a plunger reciprocally mounted in said injector cavity and a high pressure chamber formed between said plunger and said injection orifice, said plunger movable into said high pressure chamber to increase the pressure of the fuel in said high pressure chamber;
• a closed nozzle assembly mounted in said injector cavity and including a needle valve element reciprocally mounted for movement between a closed position blocking fuel flow through said injection orifice and an open position permitting fuel flow through said injection orifice;
• and
• a needle valve control means for moving said needle valve element between said open and said closed positions, said needle valve control means including a control volume positioned adjacent one end of said needle valve element, a control volume charge circuit for supplying fuel from said fuel transfer circuit, a drain circuit for draining fuel from said control volume to a low pressure drain, and an injection control valve positioned along said drain circuit for controlling the flow of fuel through said drain circuit so as to cause the movement of said needle valve element between said open and said closed positions, wherein said control volume charge circuit is integrally formed in said needle valve element.

A unit fuel injector for receiving low pressure fuel from a fuel supply and injecting the fuel at a high pressure into a combustion chamber of an engine, comprising:

• an injector body containing an injector cavity, a fuel transfer circuit and an injection orifice formed in one end of said injector body;
• and
• a plunger mounted in said injector cavity for reciprocal movement along a longitudinal axis and a high pressure chamber formed between said plunger and said injection orifice, said plunger movable into said high pressure chamber to increase the pressure of the fuel in said high pressure chamber;
• a closed nozzle assembly mounted in said injector cavity and including a needle valve element reciprocally mounted for movement between a closed position blocking fuel flow through said injection orifice and an open position permitting fuel flow through said injection orifice;
• a needle valve control means for moving said needle valve element between said open and said closed positions, said needle valve control means including a control volume positioned adjacent one end of said needle valve element, a control volume charge circuit for supplying fuel from said fuel transfer circuit, a drain circuit for draining fuel from said control volume to a low pressure drain, and an injection control valve positioned along said drain circuit in said injector cavity between said high pressure chamber and said needle valve element for controlling the flow of fuel through said drain circuit so as to cause the movement of said needle valve element between said open and said closed positions, said injection control valve including a control valve element movable along a central axis substantially parallel to said longitudinal axis into a first position to block fuel flow from said control volume and into a second position to permit fuel flow from said control volume charge circuit into said control volume and from said control volume to said low pressure drain, wherein said central axis is offset a spaced distance from said longitudinal axis;
• and
• a flow limiting means for limiting the fuel flow from said control volume to drain when said needle valve element is in said open position, said flow limiting means including a control volume inlet port fluidically connecting said charge circuit and said control volume, a control volume outlet port fluidically connecting said control volume and said drain circuit and a flow limiting valve formed on said outer end of said needle valve element for at least partially blocking said control volume inlet port and said control volume outlet port to limit fuel flow to the low pressure drain.