Patent ID: 7343895

Claim:
A fuel injection system for a gaseous fuelled internal combustion engine with. liquid pilot fuel ignition, said system comprising: (a) a pilot fuel injection valve mountable in a cylinder head of said engine and operable to inject a liquid pilot fuel directly into a combustion chamber of said engine, said pilot fuel injection valve comprising: a first valve body; a first nozzle associated with an end of said first valve body, wherein said first nozzle is positionable within said combustion chamber during a pilot fuel injection event so that said pilot fuel is introducible into said combustion chamber through said first nozzle; a pilot fuel cavity disposed within said first valve body near said first nozzle; a first valve member movable within said first valve body to stop or allow pilot fuel flow from said pilot fuel cavity to said first nozzle; a pilot fuel supply passage disposed within said first valve body and communicating between a pilot fuel supply port and said pilot fuel cavity; a cooling system operable for cooling pilot fuel held within said pilot fuel injection valve to maintain a pilot fuel temperature below the initial boiling point of said pilot fuel when said engine is running; and (b) a gaseous fuel injection valve mountable in said engine and operable to inject a gaseous fuel into an intake port for said combustion chamber or directly into said combustion chamber, said gaseous fuel injection valve comprising: a second valve body; a second nozzle associated with an end of said second valve body, wherein said gaseous fuel is introducible through said second nozzle into said intake port or directly into said combustion chamber during a gaseous fuel injection event; a gaseous fuel cavity disposed within said second valve body near said second nozzle; a second valve member movable within said second valve body to stop or allow gaseous fuel flow from said gaseous fuel cavity to said second nozzle; a gaseous fuel supply passage disposed within said second valve body and communicating between a gaseous fuel supply port and said gaseous fuel cavity; wherein said pilot fuel injection valve and said gaseous fuel injection valve cooperate together to fuel the internal combustion engine and said first nozzle is thermally insulated from said first valve body so that surfaces of said first nozzle that can come into contact with vaporized pilot fuel that is injected into said combustion chamber can maintain a temperature that is higher than the final boiling point of said pilot fuel when said engine is running.