Fuel injector having after-injection reduction arrangement

Details Fuel injector having after-injection reduction arrangement Fuel injector having after-injection reduction arrangement

2000-01-13

2001-07-10

Brinson, Patrick (Department: 3752)

Fluid sprinkling, spraying, and diffusing

Fluid pressure responsive discharge modifier* or flow...

Fuel injector or burner

C239S533900, C239S533150, C239S585400, C251S129210

Reexamination Certificate

active

06257508

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates in general to valve assemblies, and, in particular, fuel injectors having a swirl generator. More particularly to high-pressure, direct-injection fuel injectors required to meter accurate and repeatable amounts of fuel for any given injection pulse.
A high-pressure, direct-injection fuel injector is described in the above referenced applications. The fuel injector has a needle reciprocated within a fuel passageway by an armature. The armature is moved by electromagnetic force created by current that flows through a coil assembly located proximate the armature. When the electromagnetic force acts on the armature and operatively connected needle, the armature and needle overcome the load of an armature spring to lift the needle from a seat, which opens the outlet of the fuel injector to begin an injection cycle. To terminate the fuel injection cycle, the electromagnetic force is decayed and held constant until the armature and needle begin to move in the direction of the seat. When the needle fully engages the seat, the outlet of the fuel injection closes, and the injection cycle is completed.
Under certain conditions, however, the needle can rebound (bounce) when it contacts the seat. Because the needle rebounds and fails to fully engage the seat, additional fuel can be injected from the fuel outlet after the desired fuel injection cycle. That is, the valve assembly, which forms the fuel injector, allows for after-flow through the valve assembly when the valve assembly is commanded to terminate a flow cycle. In particular, the fuel injector produces after-injections, which are injections of fuel from the outlet of the fuel injector after the specified injection cycle should have terminated. During particular operative conditions, the needle can rebound numerous times, and create multiple after-injections. These multiple after-injections can reestablish injection fuel flow during the fuel outlet closing procedure. This addition fuel flow deters arcuate fuel injection calibration, which affects subsequent engine calibration. Moreover, the undesired fuel flow minimizes the ability to achieve a linear flow range (LFR) for the fuel injector.
SUMMARY OF THE INVENTION
The present invention provides a valve assembly including a housing, an armature, an armature bias spring, a needle, a seat, and a flow restrictor. The housing has an inlet, an outlet, and a passageway extending from the inlet to the outlet along a longitudinal axis. The armature is disposed within the passageway. The armature has an armature passage including a first portion and a second portion. The first portion has a first cross-sectional area. The second portion has a second cross-sectional area. The first cross-sectional area of the first portion is greater than the second cross-sectional area of the second portion.
The armature bias spring is disposed within the first portion of the armature passage. The needle is disposed within the second portion of the armature passage. The seat is located proximate the outlet. The flow restrictor is disposed between the first portion and the second portion of the armature passage of the armature. The flow restrictor includes an orifice having a third cross-sectional area that is less than the first cross-sectional area.
In a preferred embodiment, the armature is a substantially cylindrical member that has a first end surface, a second end surface, and a plurality of sections between the first surface and the second surface that provides a side surface with a stepped profile so that the diameter of the substantially cylindrical member decreases between the first surface and the second surface. The first portion of the armature passage extends from the first surface into the plurality of sections and the second portion of the armature passage extends from the second surface into the plurality of sections so that the first portion and the second portion of the armature passage engage at a transition region.
The first portion of the armature passage has a first vent aperture that communicates the first portion with the side surface, and the second portion of the fuel passage has a second vent aperture that communicates the second portion with the side surface. In a preferred embodiment, each of the first portion, second portion, the first vent aperture, and the second vent aperture is a substantially cylindrical volume. The substantially cylindrical volume of the first portion has a diameter D
1
. The substantially cylindrical volume of the second portion has a diameter D
2
, which is approximately 50% less than the diameter D
1
. The first vent aperture comprise a diameter D
3
, which is approximately 75% less than the diameter D
1
. The second vent aperture comprises a diameter D
4
, which is approximately 60% less than the diameter D
1
. The orifice of the flow restrictor has a substantially circular cross-section with a diameter D
5
, which is approximately 80% less than the diameter D
1
.
The present invention also provides a fuel injector including a housing, an armature, an armature bias spring, a needle, a seat, a swirl generator, and a flow restrictor. The fuel injector housing has a fuel inlet, a fuel outlet, and an axially extending fuel passageway from the fuel inlet to the fuel outlet along a longitudinal axis. The armature is disposed within the fuel passageway. The armature has an armature passage including a first portion and a second portion. The first portion is a first cylindrical volume with a first diameter, and the second portion being a second cylindrical volume with a second diameter. The first diameter is greater than the second diameter. The armature bias spring disposed within the first portion of the armature passage. The needle is disposed within the second portion of the armature passage. The seat is located proximate the fuel outlet, and the swirl generator is adjacent the seat. The flow restrictor is disposed between the first portion and the second portion of the armature passage. The flow restrictor includes a circular orifice with a third diameter, which is less than the second diameter.
In a preferred embodiment, the armature is a substantially cylindrical member having a first end surface, a second end surface, and a plurality of sections between the first end surface and the second end surface, the plurality of sections provides a side surface. The first portion of the armature passage has a first vent aperture that communicates the first portion with the side surface, and the second portion of the armature passage has a second vent aperture that communicates the second portion with the side surface. The preferred embodiment also has armature guide eyelet located at an inlet portion of the body. The armature guide eyelet is configured to allow fluid communication between the armature guide eyelet and the side surface of the armature.
The present invention also provides a method of generating flow from a valve assembly without allowing after-flow through the valve assembly when the valve assembly is commanded to terminate a flow cycle. The valve assembly includes a housing having an inlet, an outlet, and a passageway extending from the inlet to the outlet; an armature disposed within the passageway, the armature has an armature passage including a first portion and second portion; an armature bias spring disposed within the first portion of the armature passage; a needle disposed within the second portion of the armature passage; a seat located proximate the outlet. The method is achieved by sizing the first portion of the armature passage with a first volume and the second portion of the armature passage with a second volume, which is less than the first volume; providing a first vent aperture that communicates the first volume with a portion of the valve passageway; providing a second vent aperture that communicates the second volume with a portion of the valve passageway; and locating a flow restrictor between the first volume and the second volume.
In a preferred embodiment of the method,

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