Dual fuel injection valve and method of operating a dual fuel injection valve

A fuel injection valve operable to independently and separately inject two different fuels into a combustion chamber, said fuel injection valve comprising:

• (a) an injection valve body comprising:
• a first-fuel inlet port through which a first fuel can be introduced at injection pressure into said injection valve body;
• a first-fuel passage provided within said injection valve body and extending between said first-fuel inlet port and a first-fuel cavity;
• a second-fuel inlet port through which a second fuel can be introduced into said injection valve body;
• a second-fuel passage connecting said second-fuel inlet port to a second-fuel cavity;
• at least one first-fuel ejection port provided in said injection valve body through which said first fuel can be ejected directly into said combustion chamber from said first-fuel cavity;
• a hydraulic fluid inlet port through which pressurized hydraulic fluid can be introduced into fluid passages and a control chamber disposed within the interior of said injection valve body;
• a hydraulic fluid drain port through which hydraulic fluid can be drained from said control chamber;
• and
• a control valve that is operable to selectively direct the flow of the hydraulic fluid and control hydraulic fluid pressure within said control chamber;
• (b) a dual needle assembly comprising:
• a hollow outer needle comprising an open end and an opposite sealing end, which comprises a first sealing surface, wherein said outer needle is movable within said injection valve body between a closed position when said first sealing surface is urged against a first seat associated with said injection valve body near said first-fuel ejection port thereby preventing said first fuel from flowing through said first-fuel ejection port, and an open position when said first sealing surface is spaced apart from said first seat thereby allowing said first fuel to flow through said first-fuel ejection port;
• at least one fuel ejection port provided in said outer needle through which said second fuel can be ejected directly into said combustion chamber from said second-fuel cavity;
• a cap associated with and detached from said open end of said outer needle, wherein said cap can be dynamically disposed within said control chamber such that hydraulic fluid pressure within said control chamber can apply a force that is transmitted through said cap to said outer needle to influence the position of said cap and outer needle;
• an inner needle disposed within said outer needle, said inner needle comprising a supported end opposite to a sealing end, which comprises a second sealing surface, wherein said inner needle is movable within said outer needle between a closed position when said second sealing surface is urged against a second seat associated with said outer needle thereby preventing said second fuel from flowing through said second-fuel ejection port, and an open position when said second sealing surface is spaced apart from said second seat thereby allowing said second fuel to flow through said second-fuel ejection port;
• and
• an inner spring disposed within said inner valve body between said cap and said inner needle, whereby said inner spring contributes to biasing said inner needle in said closed position, and said inner spring can also contribute to biasing said outer needle in said closed position by expanding to space said cap away from said outer needle.

A method of operating a fuel injection valve to independently and separately inject two different fuels into a combustion chamber, wherein said fuel injection valve comprises a dual needle assembly comprising an outer needle, a cap detachedly associated with an open end of said outer needle, an inner needle disposed and movable within said outer needle, and an inner spring operatively associated with said inner needle and said cap, said method comprising:

• moving said outer needle between a closed position where it is seated against a first valve seat and an open position where it is spaced apart from said first valve seat to regulate flow of a first fuel into said combustion chamber through at least one first fuel ejection port;
• moving said inner needle between a closed position where it is seated against a second valve seat and an open position where it is spaced apart from said second valve seat to regulate flow of a second fuel into said combustion chamber through at least one second fuel ejection port;
• controlling the movements of said outer and inner needles with the movements of each needle being independent from the other;
• pressurizing a control chamber associated with said outer needle to apply a closing force to said outer needle, and reducing pressure in said control chamber to drain pressure to allow said outer needle to move to said open position;
• and
• biasing said inner needle in said closed position with said inner spring, which can also contribute to the closing force applied to said outer needle by spacing said cap from said outer needle when pressure in said control chamber is less than maximum pressure and greater than drain pressure.