Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Reexamination Certificate
2001-10-22
2003-12-23
Mar, Michael (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
C239S533200, C239S463000, C239S490000
Reexamination Certificate
active
06666387
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fuel injector of an internal combustion engine, and particularly to the improvement in the shape of an orifice nozzle tip of the fuel injector.
BACKGROUND ART
In recent years, there have been proposed and developed various swirl-type DI fuel injectors suited to direct-injection (DI) gasoline engines. One such swirl-type DI fuel injector has been disclosed in SAE Paper 2000-01-1045. The swirl-type DI fuel injector often uses a swirler located upstream of a conically or semi-spherically ended needle valve in order to give rotational momentum to fuel.
FIG. 14
shows an L-cut orifice nozzle disclosed in the SAE Paper 2000-01-1045. As seen in
FIG. 14
, an axis of nozzle hole (orifice)
4
of the L-cut orifice nozzle is identical to an axis
24
of a substantially cylindrical nozzle body
6
. The L-cut orifice nozzle tip (hereinafter is referred to as a “projected portion 20”) is semi-cylindrical in shape and has a pair of rectangular flat wall surfaces (
22
a
,
22
b
) parallel to the orifice axis identical to axis
24
of the nozzle body. In the fuel injector with the L-cut orifice nozzle disclosed in the SAE Paper 2000-01-1045, by means of the swirler the rotational momentum is given to the fuel in the orifice, so that the fuel flows or rotates in the circumferential direction of the nozzle hole.
SUMMARY OF THE INVENTION
As shown in
FIG. 13
, fuel is injected or sprayed from the nozzle hole of the L-cut orifice nozzle at a so-called fuel-flow angle (simply, a flow angle &phgr;) between a plane normal to the orifice axis and the direction of fuel flow as viewed from the vertical cross section. Flow angle &phgr; is based on both an axial fuel flow velocity component W in the orifice-axis direction and a circumferential fuel flow velocity component U in the circumferential direction of nozzle hole
4
(exactly, rotating or swirling fuel flow direction), and defined or represented by the following expression (1).
&phgr;=tan
−1
(
W/U
) (1)
On the other hand, a spray angle &agr; of the fuel is also based on both axial fuel flow velocity component W in the orifice-axis direction and circumferential fuel flow velocity component U in the circumferential direction of nozzle hole
4
, and represented by the following expression (2).
&agr;=2 tan
−1
(
U/W
) (2)
Therefore, the relationship between flow angle &phgr; and spray angle &agr; is represented as the following expression (3).
&phgr;=90°−(&agr;/2) (3)
FIG. 15
shows the spray pattern of fuel injected from nozzle hole
4
with flow angle &phgr; and spray angle &agr;. As can be seen from the spray shape shown in
FIG. 15
, a first collected fuel portion Xc and a second collected fuel portion Yc are produced. In
FIG. 15
, a plurality of arrows indicate directions of fuel injection (that is, swirling-fuel-flow direction). As seen from the perspective view shown in
FIG. 14
, on the assumption that a reference plane is a plane normal to the orifice axis and cutting a section of projected portion
20
that a height h of projected portion
20
measured in the orifice-axis direction relatively becomes smallest, and an intersection point between a central axis of the nozzle hole (i.e., the orifice axis) and the reference plane (h=0) is chosen as an origin O, an angle &thgr; is measured in a circumferential direction from a directed line radially extending from the origin O and including the intersection of the reference plane and rectangular wall surface
22
a
of the semi-cylindrical orifice nozzle tip. The height h of projected portion
20
at a certain angular position is axially measured from the reference plane. In the L-cut orifice nozzle, as shown in the fuel-spray angle characteristic shown in
FIG. 16
, spray angle &agr; varies depending on angle &thgr;. The spray pattern shown by the spray section of
FIG. 15
is described in detail in reference to
FIGS. 17-19
.
FIG. 17
shows a developed shape of semi-cylindrical projected portion
20
(the orifice nozzle tip facing the combustion chamber) in a &thgr;-h coordinate system corresponding to a cylindrical coordinate system in which a &thgr;-axis represents angle &thgr; measured in the circumferential direction from the previously-noted directed line, whereas an h-axis represents height h of projected portion
20
at a certain angular position. As can be seen from the developed shape of semi-cylindrical projected portion
20
shown in
FIG. 17
by way of the &thgr;-h coordinate system, the fuel is injected or sprayed out of the nozzle hole at the flow angle &phgr; as indicated by the arrows P, Q, and R, but part of the fuel tends to impinge on rectangular flat wall surface
22
b
of the orifice nozzle tip (see the arrow Q of FIG.
17
). As explained in more detail in reference to
FIGS. 18 and 19
, fuel sprayed through a first zone a of nozzle hole
4
produces a fuel spray within an angular range A. Fuel sprayed through a second zone b of nozzle hole
4
impinges on rectangular flat wall surface
22
b
and then flows along the wall surface. As a result of this, second collected fuel portion Yc (see
FIG. 15
) is produced in the direction substantially parallel to rectangular flat wall surface
22
b
and indicated by the arrow B. Fuel passing through a third zone o of nozzle hole
4
flows along the inner peripheral wall surface of semi-cylindrical projected portion
20
, and then sprayed through a section f of the tip end of projected portion
20
, and thus produces a fuel spray within an angular range F. Fuel passing through a fourth zone d of nozzle hole
4
flows along the inner peripheral wall surface of semi-cylindrical projected portion
20
, and then sprayed out in the direction indicated by the arrow G. Owing to the fuel sprayed out in the direction indicated by the arrow G, first collected fuel portion Xc (see
FIG. 15
) is produced. In contrast, there is no fuel sprayed through a section e of the tip end of projected portion
20
. When the fuel evaporates in the first collected fuel portion Xc, a comparatively rich air/fuel mixture results. For this reason, locating a spark plug at a position corresponding to first collected fuel portion Xc carries the advantage of reducing fuel consumption and emissions. That is, by way of better setting of the spark plug to the position corresponding to first collected fuel portion Xc, it is possible to efficiently feed the lowest possible fuel required in a lean or ultra-lean stratified combustion mode to the spark plug. This enhances the combustion stability in the stratified combustion mode.
As discussed above, in the conventional swirl-type DI fuel injector disclosed in the SAE Paper 2000-01-1045, it is possible to enhance an ignitability owing to the formation of first corrected fuel portion Xc, however, second corrected fuel portion Yc is simultaneously formed at an angular position spaced apart from the angular position of first corrected fuel portion Xc by the fuel impinging on and rebounded from rectangular flat wall surface
22
b
of the semi-cylindrical orifice nozzle tip (projected portion
20
). The two corrected fuel portions Xc and Yc tend to form a denser air/fuel mixture, thus increasing unburned hydrocarbons (HCs). First corrected fuel portion Xc brings the advantage enhancing the ignitability, whereas second corrected fuel portion Yc never offers the benefit of enhanced ignitability. That is, second corrected fuel portion Yc merely causes unburnt HC emissions.
Accordingly, it is an object of the invention to provide a fuel injector of an in-cylinder direct-injection (DI) gasoline engine, which avoids the aforementioned disadvantages.
It is another object of the invention to provide a swirl-type DI fuel injector of a DI gasoline engine, which is capable of achieving an excessively wide stratified combustion air-fuel ratio (AFR) zone and reduced fuel consumption and emissions (or improved emission control performance).
In order to accomplish the aforementioned and other objects of the present
Bui Thach H
Mar Michael
LandOfFree
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