Extended tip air assist fuel injector

A shroud member for converting an extending tip fuel injector into an air assist fuel injector wherein the air metering is performed at a distance remote from the O-ring seals holding the injector into the engine manifold.

FIELD OF INVENTION 
This invention relates to fuel injectors in general and more particularly 
to air assisted fuel injectors. 
BACKGROUND OF INVENTION 
It is the function of air assist fuel injectors to atomize the fuel into 
smaller droplets to provide a better combustion process and to minimize 
the emissions components of the exhaust gas from those which might be 
found in non-air assisted fuel systems. 
Engine emission requirements have driven the need to achieve better 
atomization of the fuel by breaking up the fuel into small droplet sizes 
that result in more thorough or efficient combustion. To accomplish this, 
additional air at sonic velocity is aimed at the fuel and the impact of 
the air results in the air energy braking up the fuel droplets into 
droplets of a fine mist which is then aimed at the intake valve. 
This has been fairly well accomplished for some engine designs, by allowing 
the point of air metering exit to be out in the open air stream. However, 
some engine designs place the point of air metering back in a recessed 
pocket or anti chamber. This typically occurs due to the geometry 
necessary to incorporate the air flow passage in the manifold or head, or 
due to the need to produce the air assist injector in a pod shaped housing 
with an external air feed connection. 
The drawbacks of having the air metering exit point in an anti chamber 
include poor targeting capability resulting in the atomized fuel being 
inadequately aimed at the intake valve or valves and the potential that 
the finely atomized mist that an air assist injector produces will 
condense on the runner wall. Both of which results in a penalty on 
emissions and derivability. 
The previous solutions require wall wetting compromises to be made in the 
calibration of the engine and subsequent emission control philosophy. 
SUMMARY OF THE INVENTION 
The solution herein allows a multipoint extended tip air assist injector to 
have the air metering point located at the fuel metering point and 
together each are substantially removed from the sealing geometry of the 
injector and the manifold in which it is mounted. The result allows 
optimizing of the targeting for the fuel and the cylinder. The atomized 
fuel from the injector is capable of being swept into the air steam and 
wall wetting and its subsequent emission and vehicle derivability problems 
are minimized. In addition the fuel charge can be aimed at the intake 
valve(s) of the engine. 
An air assisted electromechanical fuel injector for an internal combustion 
engine having an inlet for the reception of fuel into the injector and an 
outlet at one end of the injector for discharging fuel into the manifold 
of the engine. Adjacent the fuel outlet in the valve body is a fuel 
metering valve which is operated by an electromagnetic means for opening 
and closing valve. An air supply means provides air to the injector. A 
shroud member is located on the injector and in a top feed injector, 
extends from the outlet to a point intermediate the inlet and the outlet 
of the injector. The shroud member cooperates with the injector, more 
particularly with the valve body, to define air passageways between the 
valve body and the inside of the shroud means for the passage of air. An 
air inlet means in the shroud member is adapted to be in fluid 
communication with air supply means in the manifold for connecting the air 
supply means, through the air passageways to a discharge point adjacent to 
but downstream of the outlet of the fuel metering valve. Sealing means is 
located in cooperative relationship with the shroud member and the 
manifold and are axially spaced on either side of the air inlet means. 
In all embodiments, the air assisted electromechanical fuel injector may be 
either a top feed injector or a bottom feed injector and in each instance 
the design of the shroud member is modified to accommodate the fuel feed, 
air feed and sealing requirements. 
In one embodiment the air assisted electromechanical fuel injector has its 
fuel metering valve located in the air stream of the manifold of the 
engine and fuel metering and air metering are located adjacent to the 
outlet of the injector in the air stream. 
In still another embodiment, the air assisted electromechanical fuel 
injector additionally includes conduit means for connecting the air inlet 
means to the air supply means.

DETAILED DESCRIPTION 
In FIG. 1 there is illustrated a fuel injector 10 as is described in U.S. 
patent application having Ser. No. 08/268,004 and entitled "Extended Tip 
Gasoline Port Fuel Injector". The operation of an such a fuel injector 10 
is well known and will not be repeated. The fuel metering valve 11 is 
located at the end of the valve body 12 and is operated by an 
electromagnetic means such as a coil 13. Around the outside of the valve 
body 12 there is illustrated a shroud member 14 which is used to convert 
the fuel injector into an air-assist fuel injector. The shroud member 14 
is similar to that found in U.S. Pat. No. 5,174,505, entitled Air Assist 
Atomizer for Fuel Injector dated Dec. 29, 1992 by J. J. Shen with the 
exceptions duly detailed hereinafter. 
In the preferred embodiment, the shroud member 14 provides annular pockets 
16, 18 for containing O-ring seals 20, 22. The O-rings function, as 
illustrated in FIG. 2 to seal the injector 10 in the manifold 24. In 
addition, the shroud member 14 has an air inlet port 26 for receiving air 
from an air passageway 28 in the manifold 24 as illustrated in FIG. 2. 
Arrows 30 in both FIGS. show the flow of the air through the air 
passageways 32 between the shroud member 14 and the valve body 12 from the 
air inlet port 26. 
The concept in this invention is to position the point of air metering 34 
some distance from the lower seal 22 of the injector in the manifold 24 so 
that the fuel is atomized adjacent to the fuel metering tip 36 and at the 
point of the insertion of the fuel into the air stream 38 flowing in the 
manifold. In particular, FIG. 2 shows the application of the injector 10 
of FIG. 1 in an bent stream application wherein the fuel is directed to 
the intake valve 40 of the engine. 
Between the shroud member 14 and the valve body 12 of the injector 10 there 
is an air passageway 32 directing the flow of air from the manifold air 
passageway 28 through the air inlet port 26. The outline of the valve body 
12 can contain a plurality of ribs or can be smooth so long as there 
exists the air passageway 32. At the end 42 of the air passageway 32, the 
air is directed to the outlet of the injector for mixing with the fuel to 
create the fine mist. 
The shroud member 14 is a molded plastic member, or in the alternative may 
be fabricated as a sintered metal member, and is secured to the injector 
and is held in the manifold by various means. A top feed fuel injector is 
also secured to the manifold by the location of the fuel rail, not shown, 
which supplies fuel to the inlet of the injector. The injector 10 of FIG. 
1 being a top feed injector receives fuel from a fuel rail secured to the 
top of the injector. The concept of the air assist being supplied to the 
point of the fuel metering is also applicable to a bottom feed injector 
and the shroud additionally provides means for the inlet of fuel into the 
injector. In such a case, another set of O-rings will be provided to 
separate both the fuel and the air passages and to seal the injector into 
the manifold or similar engine component. 
The air metering function can be fabricated by means of one or more air 
disks at the end of the shroud member 14 as illustrated in U.S. Pat. No. 
5,174,505, or it may be accomplished by one or more apertures. In each 
embodiment the air, at sonic velocity, is directed to the fuel ejected 
from the fuel metering tip 11 of the injector. 
FIG. 3 illustrates a pod member 44 which may be attached to the injector 
10. The pod member 44 includes a tubular extension 46 from the air inlet 
means 26. A conduit member may be attached to the tubular extension for 
connecting the air inlet means 26 to an air supply means.