Dual check fuel injector and fuel system using same

A fuel system comprising:

• a plurality of fuel injectors that each comprise an injector body defining a first fuel inlet, a second fuel inlet, a first nozzle outlet set, a second nozzle outlet set and a drain outlet, and having disposed therein a first control chamber and a second control chamber;
• a first check valve member defining a through passage and being positioned entirely inside the injector body with a closing hydraulic surface exposed to a fluid pressure in the first control chamber, and being movable between a closed position in contact with a first seat on the injector body covering the first nozzle outlet set to fluidly block the first fuel inlet to the first nozzle outlet set and an open position out of contact with the first seat to fluidly connect the first fuel inlet to the first nozzle outlet set, wherein the fluid pressure present at the closing hydraulic surface in the first control chamber acts to keep or move the first check valve member in the closed position, the fluid pressure at the closing hydraulic surface when the first check valve member is in the closed position being higher than the fluid pressure for the open position of the first check valve member;
• a second check valve member positioned entirely inside the injector body with a closing hydraulic surface exposed to a fluid pressure in the second control chamber, and being movable between a closed position in contact with a second seat on the first check valve member to fluidly block the second fuel inlet to the through passage and the second nozzle outlet set, and an open position out of contact with the second seat to fluidly connect the second fuel inlet to the through passage and the second nozzle outlet set, wherein the fluid pressure present at the closing hydraulic surface in the second control chamber acts to keep or move the second check valve member in the closed position, the fluid pressure at the closing hydraulic surface when the second check valve member is in the closed position being higher than the fluid pressure for the open position of the second check valve member;
• a source of first fuel fluidly connected to the first fuel inlet;
• a source of second fuel fluidly connected to the second fuel inlet;
• an electronic controller in control communication with each of the plurality of fuel injectors;
• and
• the first fuel differing from the second fuel in at least one of chemical identity, matter phase and pressure.

A method of operating a fuel system with a plurality of fuel injectors that each comprise an injector body defining a first fuel inlet, a second fuel inlet, a first nozzle outlet set, a second nozzle outlet set and a drain outlet, and having disposed therein a first control chamber and a second control chamber;

• a first check valve member defining a through passage and being positioned entirely inside the injector body with a closing hydraulic surface exposed to a fluid pressure in the first control chamber, and being movable between a closed position in contact with a first seat on the injector body covering the first nozzle outlet set to fluidly block the first fuel inlet to the first nozzle outlet set, and an open position out of contact with the first seat to fluidly connect the first fuel inlet to the first nozzle outlet set;
• a second check valve member positioned entirely inside the injector body with a closing hydraulic surface exposed to a fluid pressure in the second control chamber, and being movable between a closed position in contact with a second seat on the first check valve member to fluidly block the second fuel inlet to the through passage and the second nozzle outlet set, and an open position out of contact with the second seat to fluidly connect the second fuel inlet to the through passage and the second nozzle outlet set;
• the method comprising the steps of:
• supplying gaseous fuel from a first common rail to the first fuel inlet;
• supplying liquid fuel from a second common rail to the second fuel inlet;
• reducing the fluid pressure present at the closing hydraulic surface in the first control chamber to keep or move the first check valve member in the open position, the fluid pressure at the closing hydraulic surface when the first check valve member is in the closed position being higher than the fluid pressure for the open position of the first check valve member;
• reducing the fluid pressure present at the closing hydraulic surface in the second control chamber to keep or move the second check valve member in the open position, the fluid pressure at the closing hydraulic surface when the second check valve member is in the closed position being higher than the fluid pressure for the open position of the second check valve member;
• injecting gaseous fuel from one of the plurality of fuel injectors through the first nozzle outlet set and the second nozzle outlet set when the first check valve member and the second check valve member are respectively in the open position;
• and
• injecting liquid fuel from the second nozzle outlet set when the second check valve member is in the open position.