Note: Descriptions are shown in the official language in which they were submitted.
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LASER DRILLED FUEL INJECTOR NOZZLES
Backqround of the Invention
The present invention relates generally to fuel
injector nozzles for use in fuel injectors, and more
S particularly to a method and apparatus for laser drilling
apertures in a single crystal sapphire substrate to form
a fuel injector nozzle.
Fuel injectors employing fuel injector nozzles for ^
metering and dispersing fuel as it is ejected are known
in the prior art. Fuel injector nozzles are typically
fabricated from a monocrystalline silicon substrate using
conventional anisotropic etching techniques. Commonly
assigned U.S. Patent No. 4,628,576 issued to Giachino et
al discloses a typical fabrication sequence for
manufacturing a silicon fuel injector nozzle using
anisotropic etching techniques. Basically, the
fabrication sequence consists of progressive steps of
growing an oxide on a silicon substrate and then
depositing or removing material until the required
aperture pattern is achieved. This technique is limited
in that only an aperture with an axis perpendicular to
the nominal plane of the silicon substrate can be
produced.
Commonly assigned U.S. Patent No. 4,808,260 issued
to Sickafus et al discloses a method for anisotropically
etching apertures in a silicon substrate such that the
aperture plane is at a preselected angle with respect to
the crystalline planes of the substrate. Each aperture
consists of two offset aperture pits etched in opposing
planar surfaces of the silicon substrate. By offsetting
the aperture pits, an aperture is formed at an angle
relative to the crystalline planes of the silicon
substrate.
A disadvantage of this method is that the angle and
cross sectional area of the aperture is limited by the
thickness of the substrate, the relative angles between
90-497 -2-
the crystalline planes of the substrate and the offset
distance between the two aperture pits. A further
disadvantage is that the aperture does not have a uniform
taper since the aperture abruptly narrows at the offset
point. Additionally, silicon substrates have experienced
problems with cleavage fracture, or splitting along a
crystalline plane. Problems have also arisen where the
apertures have irregular side walls. Any irregularity in
the aperture walls causes uneven fuel dispersion from the
fuel injector resulting in inefficient fuel combustion.
Although fabricating fuel injector nozzles by
anisotropic etching is the preferred method in the
industry, other fabrication techniques may be employed.
For example, electrodischarge machining techniques have
been used to fabricate metallic fuel nozzles. However,
these manufacturing techniques are complicated, labor
intensive, and time consuming. Moreover, metallic fuel
injector noæzles are expensive and subject to reliability
problems due to wear from exposure to fuel and fuel
contaminants.
Accordingly, the need exists in the art to provide a
method and apparatus for fabricating fuel injector
nozzles having apertures of controlled taper, uniform
cross section and extremely smooth walls, but without the
limitations and problems associated with the previous
fabrication methods and apparatuses.
Summary of the Invention
The present invention meets that need by
providing a method for fabricating fuel injector nozzles
by laser drilling apertures into a crystalline substrate.
By laser drilling the apertures in the crystalline
substrate, the diameter and taper of an aperture can ~e
controlled independently of the crystal lattice structure
and thickness of the substrate.
90-497 3 ~ .3~ t~
In accordance with one aspect of the invention,
a method for fabricating a fuel injector nozzle is
provided wherein a crystalline substrate is positioned in
alignment with a laser beam having a wavelength .
absorbable by the substrate. The laser beam produces the
necessary apertures in the substrate independently of its
crystal lattice structure and thickness. Preferably, a
carbon dioxide laser is used on a single crystal sapphire
substrate.
The present invention also provides a fuel
injector for use in an internal combustion engine having
a fuel injector nozzle produced by the aforementioned
method. The fuel injector includes an injector body
having an inlet for communicating with a fuel source, an
outlet for ejecting fuel from the body and an inner
passageway between the inlet and the outlet. A fuel
valve regulates the fuel ejection from the outlet to the
fuel injector nozzle. The fuel injector nozzle,
preferably comprised of single crystal sapphire, meters
and disperses the fuel upon ejection from the outlet. A
retainer secures the fuel injector nozzle against the
fuel injector body, thereby substantially sealing the
interface between the fuel injector nozzle and the outlet
from fuel leakage.
Accordingly, the present invention
advantageously provides a fuel in~ector nozzle with
apertures of controlled taper, uniform cross-sectional
area and extremely smooth side walls. Further, the taper
and cross-sectional area of the aperture is independent
of the crystal lattice structure and thickness of the
substrate. These, and other advantages of the present
invention, will become apparent from the following
detailed description, the accompanying drawings, and the
appended claims.
~rief Description of the Drawings
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Fig. 1 is a top perspective view of a fuel
injector nozzle in accordance with an embodiment of the
present invention;
Fiy. 2 is a perspective view of a laser
drilling apertures in a substrate to produce a fuel
injector nozzle such as illustrated in Fig. 1; and
Fig. 3 is a cross-sectional view of a fuel
injector containing the fuel injector nozzle of the
present invention.
Detailed Description of the Invention
Referring now to Fig. 1, a fuel injector
nozzle, generally designated by reference numeral 100,
for metering and dispersing fuel in an internal
combustion engine (not shown) is illustrated. The fuel
injector nozzle 100 includes a substantially planar
substrate 102 comprised of a crystalline material,
preferably single crystal sapphire. The single crystal
nature of sapphire provides a uniform material devoid of
inclusions and grain structure. Additi~nally, the
rhombohedral crystal structure of sapphire provides a
greater increased resistance to cleavage as compared to
prior nozzle materials. The nozzle 100 may be fabricated
from conventional single crystal sapphire sheets or
ribbons such as those produced by the well-known Saphikon
edge-defined film-fed growth method.
An array of apertures 108 having tapered walls
112 and clrcular cross-sectional areas serve to guide the
fuel as it flows through nozzle 100. While fuel injector
nozzle 100 is illustrated as having an array of four
tapered apertures 108, it will be apparent to one skilled
in the art that other aperture patterns may also be
advantageously utilized.
Reference is now made to Fig. 2 which
illustrates a laser-based system 200 for fabricating fuel
injector nozzle 100 in accordance with the present
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invention. A crystalline substrate 204, preferably
comprised of single crystal sapphire, is aligned with a
laser 202, which produces a laser beam 206 having a
wavelength absorbable by substrate 204. Consequently,
when laser beam 206 strikes substrate 204, the energy of
laser beam 206 is absorbed by substrate 204 and converted
into heat. The intense heat created by laser beam 206
vaporizes substrate 204 and produces aperture 20B. For a
substrate comprised of single crystal sapphire, laser 202
is preferably a conventional carbon dioxide laser which
produces a laser beam with a wavelength of 10.6 ~m.
Preferably the exit diameter of aperture 208 is
approximately .2mm. However, the diameter of aperture
208 and the taper of aperture walls 210 are controlled by
focusing laser beam 206 in a conventional manner.
- Referring now to Fig. 3, a fuel injector,
generally designated by reference numeral 300, is shown
wherein the fuel injector nozzle of the present invention
may be advantageously used. Fuel injector 300 comprises
20 an injector body 304 having an inlet 306 for
communicating with a fuel source (not shown) and an
outlet 308 for providing fuel to nozzle 302. The fuel
injector 300 further includes an inner passageway 310
which communicates with inlet 306 and outlet 308.
Positioned within inner passageway 310 of
injector body 300 is needle valve 312, which serves to
regulate the amount of fuel ejected from outlet 308.
Needle valve 312 comprises a needle 314 and seat 316,
upon which needle 314 sits while located at its closed
position. A well-known solenoid-type actuator and spring
return means (not shown) is included within the injector
body 304 to move needle 314 upwardly and downwardly
within inner passageway 310 and thus regulate the fuel
being ejected from outlet 308.
3s Fuel injector nozzle 302 is retained against a
bottom wall 316 of injector body 304 by retaining ring
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31~. As previously described, fuel injector nozzle ~02
includes an array of apertures 108 for metering and
dispersing fuel into a spray as it is ejected from outlet
308. In response to a signal to eject fuel from the fuel r
S injector 300, the conventional actuator means lifts the
needle 314 from its seat 316 to allow fuel to flow
through apertures 108. As the fuel exits apertures 108,
it is atomized to increase combustion efficiency. It is
further contemplated by the present invention, that the
10 fuel injector nozzle may be comprised of two nozzle
plates bonded together. Such a fuel injector nozzle is
disclosed in commonly assigned U.S. Patent No. 4,828,184
issued to Gardner et al, the disclosure of which is
hereby incorporated by reference.
lS While certain representative embodiments and
details have been shown for purposes of illustrating the
invention, it will be apparent to those skilled in the
art that various changes in the methods and apparatus
disclosed herein may be made without departing from the
20 scope of the invention, which is defined in the appended
claims.
What is claimed is:
