Fuel injector with injection rate control

A closed needle injector assembly for injecting fuel into the combustion chamber of an engine, comprising:

• an injector body containing an injector cavity and a plurality of injector orifices communicating with one end of said injector cavity to discharge fuel into the combustion chamber, said plurality of injector orifices including an inner set of orifices and an outer set of orifices, said injector body including a fuel transfer circuit for transferring supply fuel to said plurality of injector orifices;
• an inner needle valve element positioned in said injector cavity for controlling fuel flow through said first set of injector orifices and an inner valve seat formed on said injector body, said inner needle valve element movable from a closed position against said inner valve seat blocking flow through said inner set of injector orifices to an open position permitting flow through said inner set of injector orifices;
• an outer needle valve element positioned in said injector cavity for controlling fuel flow through said outer set of injector orifices and an outer valve seat formed on said injector body, said outer valve element movable from a closed position against said outer valve seat blocking flow through said outer set of injector orifices to an open position permitting flow through said outer set of injector orifices;
• an inner control volume positioned adjacent an upper end of said inner needle valve element for receiving fuel;
• an outer control volume positioned adjacent an upper end of said outer needle valve element for receiving fuel;
• a drain circuit for draining fuel from said inner and said outer control volumes to a low pressure drain;
• an injection control valve positioned along said drain circuit for controlling the flow of fuel through said drain circuit to permit movement of said inner and said outer needle valve elements between said open and said closed positions, said injection control valve movable from a closed position to an open position and from the open position to the closed position to define a control event, said injection control valve operable to create a first control event permitting movement of said inner needle valve element to the open position while maintaining said outer needle valve element in said closed position to define a low fuel injection rate event;
• and
• a sequencing device mounted on said injector body adjacent said drain circuit to permit movement of both said inner and said outer needle valve elements to respective open positions during a second control event following said first control event to define a primary fuel injection event.

A method of injecting fuel into the combustion chamber of an engine, comprising the steps of:

• providing an injector body containing an injector cavity and a plurality of injector orifices communicating with one end of said injector cavity to discharge fuel into the combustion chamber, said plurality of injector orifices including a first set of orifices and a second set of orifices, said injector body including a fuel transfer circuit for transferring supply fuel to said plurality of injector orifices;
• providing a first needle valve element positioned in said injector cavity for controlling fuel flow through said first set of injector orifices and a first valve seat formed on said injector body, said first needle valve element movable from a closed position against said first valve seat blocking flow through said first set of injector orifices to an open position permitting flow through said first set of injector orifices;
• providing a second needle valve element positioned in said injector cavity for controlling fuel flow through said second set of injector orifices and a second valve seat formed on said injector body, said second valve element movable from a closed position against said second valve seat blocking flow through said second set of injector orifices to an open position permitting flow through said second set of injector orifices;
• providing a first control volume positioned adjacent an upper end of said first needle valve element for receiving fuel;
• providing a second control volume positioned adjacent an upper end of said second needle valve element for receiving fuel;
• providing a drain circuit for draining fuel from said first and said second control volumes to a low pressure drain;
• providing a single injection control valve positioned along said drain circuit for controlling the flow of fuel through said drain circuit to permit movement of said first and said second needle valve elements between said open and said closed positions, said injection control valve movable from a closed position to an open position and from the open position to the closed position to define a control event;
• moving said first needle valve element to the open position while maintaining said second needle valve element in said closed position during a first control event to define a low fuel injection rate event;
• moving both said first and said second needle valve elements to respective open positions during a second control event following said first control event to define a primary fuel injection event.

A closed nozzle injector assembly for injecting fuel into the combustion chamber of an engine, comprising:

• an injector body containing an injector cavity and a plurality of injector orifices communicating with one end of said injector cavity to discharge fuel into the combustion chamber, said plurality of injector orifices including an inner set of orifices and an outer set of orifices, said injector body including a fuel transfer circuit for transferring supply fuel to said plurality of injector orifices;
• an inner needle valve element positioned in said injector cavity for controlling fuel flow through said first set of injector orifices and an inner valve seat formed on said injector body, said inner needle valve element movable from a closed position against said inner valve seat blocking flow through said inner set of injector orifices to an open position permitting flow through said inner set of injector orifices;
• an outer needle valve element positioned in said injector cavity for controlling fuel flow through said outer set of injector orifices and an outer valve seat formed on said injector body, said outer valve element movable from a closed position against said outer valve seat blocking flow through said outer set of injector orifices to an open position permitting flow through said outer set of injector orifices;
• an inner control volume positioned adjacent an upper end of said inner needle valve element for receiving fuel;
• an outer control volume positioned adjacent an upper end of said outer needle valve element for receiving fuel;
• a drain circuit for draining fuel from said inner and said outer control volumes to a low pressure drain;
• an injection control valve positioned along said drain circuit for controlling the flow of fuel through said drain circuit to permit movement of said inner and said outer needle valve elements between said open and said closed positions, said injection control valve movable from a closed position to an open position and from the open position to the closed position to define a control event, said injection control valve operable to create a first control event permitting movement of said inner needle valve element to the open position while maintaining said outer needle valve element in said closed position to define a low fuel injection rate event;
• and
• a sequencing device mounted on said injector body adjacent said drain circuit to vary an effective outlet orifice flow area in said drain circuit for controlling fuel flow from said outer control volume.

A method of injecting fuel into the combustion chamber of an engine, comprising:

• providing an injector body containing an injector cavity and a plurality of injector orifices communicating with one end of said injector cavity to discharge fuel into the combustion chamber, said plurality of injector orifices including a first set of orifices and a second set of orifices, said injector body including a fuel transfer circuit for transferring supply fuel to said plurality of injector orifices;
• providing a first needle valve element positioned in said injector cavity for controlling fuel flow through said first set of injector orifices and a first valve seat formed on said injector body, said first needle valve element movable from a closed position against said first valve seat blocking flow through said first set of injector orifices to an open position permitting flow through said first set of injector orifices;
• providing a second needle valve element positioned in said injector cavity for controlling fuel flow through said second set of injector orifices and a second valve seat formed on said injector body, said second valve element movable from a closed position against said second valve seat blocking flow through said second set of injector orifices to an open position permitting flow through said second set of injector orifices;
• providing a first control volume positioned adjacent an upper end of said first needle valve element for receiving fuel;
• providing a second control volume positioned adjacent an upper end of said second needle valve element for receiving fuel;
• providing a drain circuit for draining fuel from said first and said second control volumes to a low pressure drain;
• providing a single injection control valve positioned along said drain circuit for controlling the flow of fuel through said drain circuit to permit movement of said first and said second needle valve elements between said open and said closed positions, said injection control valve movable from a closed position to an open position and from the open position to the closed position to define a control event;
• moving said first needle valve element to the open position while maintaining said second needle valve element in said closed position during a first control event to define a low fuel injection rate event;
• varying an effective drain flow area in said drain circuit for controlling fuel flow from said second control volume to cause movement of said second needle valve element to an open position during a second control event following said first control event to define a primary fuel injection event.