Two-stage plunger for rate shaping in a fuel injector
AssigneeCaterpillar Inc.
InventorEric N. Graves
Life of this patent
Estimating the term…
Abstract
The staged plungers can be incorporated into virtually any type of fuel injector that utilizes plunger movement to raise fuel pressure in order to initiate and sustain an injection event. The staged plungers include an outer plunger with a rate shaping spill port. An inner plunger having a rate shaping bore is positioned to reciprocate within the inner bore of the outer plunger. A compression spring biases the inner plunger toward an advanced position relative to the outer plunger. Toward the beginning of the staged plungers' downward stroke at the beginning of an injection event, their relative movement produces rate shaping in the fuel leaving the injector as well as producing a split injection as the rate shaping spill bore of the inner plunger opens to the rate shaping spill port of the outer plunger.
Claims18
A fuel injector comprising:
- an injector body having a plunger bore that opens to a fuel supply passage and a nozzle chamber, and having a piston bore, and also a nozzle outlet that opens to said nozzle chamber;
- a piston positioned to reciprocate in said piston bore between an upper position and a lower position;
- an outer plunger having an inner bore and being positioned to reciprocate in said plunger bore between an advanced position and a retracted position;
- an inner plunger positioned to reciprocate in said inner bore of said outer plunger between an advanced position and a retracted position;
- means for biasing at least one of said outer plunger and said inner plunger a distance away from said piston;
- portions of said plunger bore, said outer plunger and said inner plunger defining a fuel pressurization chamber that opens to said nozzle chamber;
- a check valve positioned in said fuel supply passage and being operable to prevent flow of fuel from said fuel pressurization chamber back into said fuel supply passage;
- a needle check positioned to reciprocate in said nozzle chamber between a closed position that closes said nozzle outlet and an open position that opens said nozzle outlet, said needle check including at least one hydraulic lift surface exposed to said nozzle chamber;
- and
- means, within said injector body, for biasing said needle check toward said closed position.
A fuel injector comprising:
- an injector body having a plunger bore that opens to a fuel supply passage and a nozzle chamber, and having a piston bore, and also a nozzle outlet that opens to said nozzle chamber;
- a piston positioned to reciprocate in said piston bore between an upper position and a lower position;
- an outer plunger having an inner bore and being positioned to reciprocate in said plunger bore between an advanced position and a retracted position;
- an inner plunger positioned to reciprocate in said inner bore of said outer plunger over a rate shaping distance;
- portions of said plunger bore, said outer plunger and said inner plunger defining a fuel pressurization chamber that opens to said nozzle chamber;
- at least one of said inner plunger and said outer plunger having a rate shaping spill port that opens said fuel pressurization chamber to a low pressure spill passage over a portion of its downward stroke;
- a check valve positioned in said fuel supply passage and being operable to prevent flow of fuel from said fuel pressurization chamber back into said fuel supply passage;
- a needle check positioned to reciprocate in said nozzle chamber between a closed position that closes said nozzle outlet and an open position that opens said nozzle outlet, said needle check including at least one hydraulic lift surface exposed to said nozzle chamber;
- and
- means, within said injector body, for biasing said needle check toward said closed position.
Dependencies are inferred from the claim text.