Common rail injector with separately controlled pilot and main injection

A fuel injection system comprising:

• a source of intermediate pressure fuel;
• a low pressure fuel reservoir;
• at least one fuel injector having a pressure intensifying mechanism, needle valve, a flow control valve and a injector body defining a nozzle outlet and a needle control chamber fluidly connected to an unobstructed needle control spill outlet and a fuel inlet;
• an intermediate pressure supply line extending between said source of intermediate pressure fuel and said fuel inlet;
• a low pressure vent line located outside said injector body and extending between said needle control spill outlet and said low pressure reservoir;
• and
• a pressure release valve positioned in said vent line and having a first position in which said vent line is closed, and a second position in which said vent line is open.

A fuel injection system comprising:

• a source of intermediate pressure fuel;
• a low pressure fuel reservoir;
• at least one fuel injector having a pressure intensifying mechanism, a needle valve, a flow control valve and an injector body defining a nozzle outlet and a needle control chamber fluidly connected to a needle control spill outlet and a fuel inlet;
• an intermediate pressure supply line extending between said source of intermediate pressure fuel and said fuel inlet;
• a low pressure vent line extending between said needle control spill outlet and said low pressure reservoir;
• a pressure release valve positioned in said vent line and having a first position in which said vent line is closed, and a second position in which said vent line is open;
• wherein said at least one fuel injector is a plurality of fuel injectors;
• and
• a flow switch positioned between said pressure release valve and said needle control spill outlet of each said fuel injector, and said flow switch having a plurality of positions, a different fuel injector being fluidly connected to said pressure release valve at each of said plurality of positions.

A method of fuel injection, comprising the steps of:

• injecting fuel at an intermediate pressure at least in part by fluidly connecting a nozzle chamber of a fuel injector to a source of intermediate pressure fuel;
• injecting fuel at a high pressure at least in part by exposing a pressure intensifying mechanism to the source of intermediate pressure fuel;
• and
• said injecting steps each include a step of moving a pressure release valve located outside the fuel injector. from a closed position to an open position.

A fuel injection system for an engine having a plurality of cylinders, comprising:

• a source of intermediate pressure fuel;
• a low pressure fuel reservoir;
• a pressure intensifying mechanism, a flow control valve and an injector body associated with each engine cylinder, and each injector body defining a nozzle outlet and a needle control chamber fluidly connected to an unobstructed needle control spill outlet and a fuel inlet;
• at least one intermediate pressure supply line extending from said source of intermediate pressure fuel to said pressure intensifying mechanism and to said fuel inlet;
• a low pressure vent line located outside said injector body and extending between said needle control spill outlet and said low pressure reservoir;
• and
• a pressure release valve positioned in said vent line and having a first position in which said vent line is closed, and a second position in which said vent line is open.

A fuel injection system for an engine having a plurality of cylinders, comprising:

• a source of intermediate pressure fuel;
• a low pressure fuel reservoir;
• a pressure intensifying mechanism, a flow control valve and an injector body associated with each engine cylinder, and each injector body defining a nozzle outlet and a needle control chamber fluidly connected to a needle control spill outlet and a fuel inlet;
• at lease on intermediate pressure supply line extending from said source of intermediate pressure fuel to said pressure intensifying mechanism and to said fuel inlet;
• a low pressure vent line extending between said needle control spill outlet and said low pressure reservoir;
• a pressure release valve positioned in said vent line and having a first position in which said vent line is closed, and a second position in which said vent line is open;
• a low pressure vent line associated with each engine cylinder;
• and
• a flow switch positioned between said pressure release valve and each said needle control spill outlet, and said flow switch having a plurality of positions, a different low pressure vent line being fluidly connected to said pressure release valve at each of said plurality of positions.