US 6,439,202 B1Granted

Hybrid electronically controlled unit injector fuel system

AssigneeCummins Inc.

InventorsJohn T. Carroll, III, Donald J Benson, Lester L Peters

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Abstract

An improved fuel injection system is provided which incorporates a common rail and a plurality of unit injectors which function together to efficiently produce various injection rate shapes and different combinations of discreet and blended pilot, main, post and after treatment fuel injection events during a single injection. The fuel injection system effectively permits flexible, responsively timed, square shaped, discreet low to mid pressure level injections utilizing the fuel pressure of the common rail while also allowing the unit injector portion to function independently to produce flexible and responsively timed and pressure controlled, triangular shaped high pressure fuel injection events and to recover excess energy. In one embodiment, a separate common rail pump is avoided by utilizing the unit injector plunger to replace fuel into the common rail which was previously injected.

Claims24

Dependent claims

A fuel injection system for controlling fuel injection into combustion chambers of a multi-cylinder internal combustion engine, comprising:

a low pressure fuel supply for supplying fuel at a low supply pressure level;
a common rail fluidically connected to said low pressure fuel supply and containing injection fuel at a common rail pressure level greater than said low supply pressure level;
a plurality of fuel injectors connected to said common rail to receive fuel from said common rail and inject fuel at a high pressure level greater than said common rail pressure level, each of said plurality of injectors including
an injector body containing an injector cavity, a fuel transfer circuit, an injection orifice formed in one end of said injector body,
a plunger reciprocally mounted in said injector cavity for movement through advancement and retraction strokes and a high pressure chamber formed between said plunger and said injection orifice, said plunger movable through said advancement stroke to at least one of increase the pressure of fuel in said high pressure chamber to a high pressure level greater than said common rail pressure level and spill fuel to said common rail,
a nozzle assembly including a needle valve element reciprocally mounted for movement between a closed position blocking fuel flow through said injection orifice and an open position permitting fuel flow through said injection orifice,
a needle valve control device adapted to move said needle valve element between said open and said closed positions to initiate an injection event;
a pump control valve for controlling the flow of fuel into said high pressure chamber;
wherein the injection system is operable in a first mode to inject fuel at said common rail pressure through said injector orifice into a combustion chamber, in a second mode to inject fuel during spilling of fuel from said high pressure chamber to one of a supply rail and said common rail as said plunger moves through said advancement stroke and a third mode to inject fuel at said high pressure level during movement of said plunger through said advancement stroke.

6 more elements

A fuel injection system for controlling fuel injection into combustion chambers of a multi-cylinder internal combustion engine, comprising:

a low pressure fuel supply for supplying fuel at a low supply pressure level;
a common rail fluidically connected to said low pressure fuel supply and containing injection fuel at a common rail pressure level greater than said low supply pressure level;
a plurality of fuel injectors connected to said common rail to receive fuel from said common rail and inject fuel at a high pressure level greater than said common rail pressure level, each of said plurality of injectors including
an injector body containing an injector cavity, a fuel transfer circuit, an injection orifice formed in one end of said injector body,
a plunger reciprocally mounted in said injector cavity and a high pressure chamber formed between said plunger and said injection orifice, said plunger movable into said high pressure chamber to increase the pressure of fuel in said high pressure chamber to a high pressure level greater than said common rail pressure level,
a nozzle assembly including a needle valve element reciprocally mounted for movement between a closed position blocking fuel flow through said injection orifice and an open position permitting fuel flow through said injection orifice,
a needle valve control device adapted to move said needle valve element between said open and said closed positions to initiate an injection event to inject fuel at said common rail pressure when the injection system is operating in a first mode and at said high pressure level when the injection system is operating in a third mode, said needle valve control device including a control volume, a drain circuit for draining fuel from said control volume to a low pressure drain, and an injection control valve positioned along said drain circuit for controlling the flow of fuel through said drain circuit so as to cause the movement of said needle valve element between said open and said closed positions;
and
a pump control valve for controlling the flow of fuel into said high pressure chamber.

6 more elements

Dependencies are inferred from the claim text.