Note: Descriptions are shown in the official language in which they were submitted.
~067357
BACKGROUND OF THE INVENTION
In the operation of internal combustion engines,
it is known that to form a stratified charge wi~hin the
engine cylinders offers a number of operating advantages.
For one thing, the provision of a stratified charge condition
within some engines permits the use of a wider variety of
fuels than is normally found with a premixPd, carbureted
charge. Further, by the proper regulation of the fuel
flow, and its subsequent combustion, the combustion process
can be csmpleted quickly and efficiently thexeby obtaining
maximum power rom the amount of fuel utilized.
It has also been determined that through the
proper regulation of fuel and air introdu¢tion to the engine
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cylinders, the resulting quality of air polluting elements
contained in the engine exhaust gas can be regulated. These
air pollutin~ elements such as NO and CO can be minimized
~to a point where they are in compliance with stric~ standards
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which are set, and which are considered to be safe for auto-
motive operation.
Toward ~acilitating the combustion process in an
; 20 internal combustion engine, the use of a cavity or depression
formed into the ~ace of a piston is known. Such a cavity
serves the unction of not only providin~ an initial com-
bustion chambe~, but also, as in the present instance,
increases the swirl rate of air which is introduced prior
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to forming the combustible charge.
As taught in U.S.P. 3,094,974, the controlled
production o~ a swirling air stream, when coordinated with
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the rate of introduction o~ fuel, results in a highly ef~icient
~ internal combustion engine operation. In said engine a
30 predetermined quantity of fuel is injected into the -
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combustion chamber, and an air stream is introduced through
the engine intake valve by means of a shaped port, or
similar means such that the entering air stream forms a
rapidly rotating mass guided by the walls of ~he combustion
chamber. The direction of swirl is such that air travels
from the fuel injection nozzle toward ~he spark plug.
As noted hereln a cavity formed in the piston
tends to promote swirling of incoming air. More specifically,
air is aspirated into the engine combustion chal~er and -
caused to initially swirl by virtue of the intake valve shape.
Thereafter, on the compression stroke, the rate of swirl is
increased as the air is compressed into the combustion
chamber and the small diameter piston cavity.
Although the concept of a cavity formed within a
piston face has been utilized in several forms and variations -
to achieve varying purposes, the desired uniform charge
formîng criteria has not been fully attained. For example,
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the cavity-configuration within a piston has been shown by
the prior art~in the form of a simple cup-like arrangement
wherein the latter is provided with cylindrical walls
opening at the piston face. Also, the use of a~substantially
spherical cavity which opens onto the plston face is known.
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In either instance the primary purpose of these depressed
i cup formations has been to form either a preliminary com-
bustion chamber, or the means for promoting the rapid swirl
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of air through the cup and through the cylindrical combustion
chamber.
A~primary object of the present invention then is
to provide an internal combustion engine piston construction
having cavity means formed in the piston face, capable of
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promoting a more rapid, controlled combustion of a charge.
A further object is to provide a piston having
a relatively shallow cavity formed therein and terminating
at the piston Eace, which cavity will receive a stxeam of
fuel as well as swirling air, whereby to force an efficient
mixing of the two into a combustible charge.
Still another object is to provide a piston .
cavity having such a configuration at the access opening '~
thereof that exiting air and combustion gases will be so ~ ;
intermixed to assure a more uniform and rapid combustion of
the charge~ ,
Another object is the provision of a piston cavity
which forms a confining passage for swirling air and com~
bustion gases prior to the'latter entering the main combustion ' ~
chamber. ,,
The above noted objectives are achieved, and the
~desired efficient operation of an internal combustion engine'
is obtained in the present invention by providing means for
introducing a swirling air charge to the engine's one or
20 more cylinders on the intake stroke of eaah. Each piston '~
is provided with a relatively shallow cavity having a central
axis extending substantially parallel to the pis,ton axis and ',
opening at t~e piston face.
Said shallow cavity functions to accelerate the
rate of the swirling air, while receiving a stream of fuel
~rom an injector or the like. An overhanging, non-uniform
lip extends inwardly across a part of the cavity thereby
defining an upstanding restriction to the ~luid flaw. This
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flow restriction lies in a plane substantially normal to the
cavity central axis. Thus, as the piston retreats from
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~067357
top dead center position during the power stroke, combustion
products including pollutants within the cavity mix
vigorously with air passing from the cavity and air a~ove -
the cavity.
DESCRIPTION OF THE DRAWINGS ~ -
Figure l is a vertical elevation in cross section
showing a piston of the type contemplated. Figure 2 lS an
environmental view of an engine into which the cylinder is .'!.. "' ~ "
incorporated. Figure 3 is similar to Figure l showing the
piston in a receded position. Figure 4 is a cross sectional
view showing the upper side of the piston of Figure l.
.
Figure 5 is a sectional view taken along line 5-5 in Figure
4.
Referring to Figure 2, an internal combustion
engine l0 of the type presently contemplated is shown
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generally as cGmprising a plurality of cylinders, each of
which slidably positions a piston. The engine shown for
~illustrating the invention is ganerally of the in-line
.
cylinder type utilizing fuel injection for forming the
~0 ~combustible charge. The fuel in such an ins~ance is metered
~to eaoh cylinder ~rom a fuel metering pump 12 which is in
turn communicated with a source of fuel such as a tank 15
or the like~. ~h .. .,.'
Normally, operation of the shown engine is through
a single actuator or control lever ll which is connected to
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fuel p~mp 12 whereby to vary the amount of fuel introduced
to~each~cylinder to mix with incoming air. Fuel quantity
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is regulated in accordance with the engine load and speed.
Air is generally lntroduced to the cylinder through
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~i67357
an intake manifold 13 which is in turn provided with an air
cleaner 14 or the like at the manifold inlet. An exhaust gas
header 16 connected to each of the respective cylinders
receives hot exhaust gases which can be conducted to a cata-
lytic converter or muffler 17 prior to being passed to the
atmosphere.
Referring to Figure 1, the cylinder 21 shown is
representative of the type cylinder normally utilized in
an internal combustion engine. For example, such an engine
generally embodies a plurality of such cylinders which can
be as arranged in an in-line relationship. The respective
cylinders are formed in the engine block 22, each cylinder ;
having a piston 23 reciprocably mounted for movement through
the cylinder bore.
Piston 23 includes an upper end or head, having
a face 24, and a skirt 26 at the piston lower end. A
conneoting rod 19, is operably connected to piston 23 in the
usual manner by way of a wrist pin 20 which~permits the
oscillatory motion of the piston. The connecting rod is
journalled at its opposite end to the engine crankshaft 18.
Each piston 23 i normally provided with a
plurality of compression and oil retaining rings 27 and 28
s1idab1y mounted in a series o longitudinally spaced apart
~ groove~ in the piston's periphery. Thus, as piston 23
f~ ~ ~ passes through cylinder bore 21, the respective xings in
expanded condition engage the adjacent cylinder walls
providing a sliding seal therewith.
The engine lO upper end is provided with a
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gasket 29 and a head 31. Each cylinder 21 as shown in
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Figure 5 is further provided with at least one intake
valve 32 and an exhaust valve 32a. Said valves are operably
connected through a common shaft or other suitable means
to be sequentially actuated in accordance with the driving
cycle of the engine.
Each engine cylinder is provided with a removable
fuel injector 33 which traverses the cylinder head 31 wall.
Said injector 33 includes an orifice 34 at the internal end,
being disposed within the cylinder combustion chamber to
assume a desired location with respect to the piston.
The outer or external end of injector 33 is
communicated through a line 36 to fuel pump 12 whereby ~uel
is introduced to each cylinder combustion chamber for a
period of time approximating the cylinder travel in the
vicinity of the top dead center position during the com-
pression stroke.
.
- The charge firing means in the present instance
includes a spark plug 37 carried in the cylinder head of
each cylinder, having the spark terminals positioned adjacent
to the injector nozzle 34. Thus, as an integral part of
the engine ignition system, the spark plug functions to
ignite a rich combustible fuel-air mixture. The latter is
formed initially in a localized area, between air within the
combustion chamber 40 and the stream of ~uel delivered from
the fuel injector.
Referring to Figure 5, in the present engine, air
is introduced into each combustion chamber 40 in a manner to
be formed into a rotating or swirling mass about said chamber.
~; This is achie~ed through intake valve 32 which, as noted,
can be provided with a shroud or other ~low guide means.
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Th~ls, air entering said intake valve 32 by way of intake
inlet manifold 13 is directed into the cylinder and is
immediately caused to swirl rapidly thereabout.
Piston 23 is provided at the upper end with a
cavity 38 which forms an annular passage entirely within the
piston. The cavity is arranged pre~erably concentric with
the piston central axis. As shown, cavity 38 assumes the
general configuration of a cylindrical walled cup havin~ a
diameter D that is less than the diameter of the piston. -
The lower end of the cavity defining the annular passage
comprises a planar end wall 3g which merges with the
cylindrical peripheral wall at junction 41. ~ -
Toward achieving the objectives of the invention,
an overhanglng portion or non-uniform lip 35 extends across
and covers a segment of cavity 38 to define a quasi-closed
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annular passage 44 within the latter. Sinca air and/or
combustion gases will~normally be swirling through cavity 38,
they will be urged toward and be guided by the cavity
; peripheral walls. Further, such combustion gases will be
flung radially-outwardly due to centrifugal force and
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con~equently will be confined within the three sided passage
44.
Referring to Figure 1, on the power stroke piston
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23 will commence at the top dead center position. Compression
compartment 40 as herein noted is illustrated in exaggerated ~ -
proportions. In actuality, at the top dead center position,
oompartment 40 will be defined by a thin, disc-like chamber
above and lmmediately adjacent to piston face 24.
On the cylinder power skroke ~uel is ~oraibly
injected into cavity 38 from in~ector 33. The liquid fuel,
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usually in droplet form, will be swept up by the swirling
air mass such that a rich fuel-air mixture will be formed
in a localized area adjacent to ~he point of injection.
As the rich mixture passes spark plug 37, the
latter is energized to initiate burning of the mixture. The
resulting flame will then continue to flow at a rapid rate
about annular passage 44 accompanied by the hot expanding
combustion gases.
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To accommodate this expanding, static mass the
upper wall 4~ of passage 44 as shown in Figure 5 extends
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progressively closer toward the cavity 38 center. This
partially enclosed arrangement will maintain the bulk of
the swirling gas withln the passage's confined portion.
To achieve complete and rapid combustion of the
remaining lean charge in the cylinder, the prbgressing flame
ront will propagate toward the center of cavity 38, as well
as through opening 43. Thus, and referring to Figure 5,
~while passage 44 becomes progressively larger in cross
section between points A and B, it will similarly become
20~ decreasingly smaller between points B and A.
Therefore, a piston 23 is driven downwardly from
top dead~center position during the power~stroke, air in a
swirIing mass beneath opening 43 of cavity 38 will tend to
leave the latter. Further, since passage 44 becomes
progressively smaller as it approaches opening 43, flame and
hot combustion gases will extend outwardly through said ~ ;
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opening and into combustion chamber 40. As further shown :
in Figures 4 and 5, the inner edge of lip 35 defines an
opening 43 to achieve the effect of progres~ively widening ~ -
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30 through opening 43. ~aid opening, preferably in the form of ;;
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673~i7
a generally cylindrical configuration, can assume other
yeometrical configurations to achieve the desired action
and purpose of the invention as herein described.
For example, opening 43 can be of sufficient
diameter to be positioned entirely within one segment of
wall 42. Also as shown, to aid fluid flow between passage 44
and combustion chamber 40, opening 43 is positioned to have
one portion of its edge contiguous with the wall segment of
cavity 38 therebelow. However, the size and disposition of -
opening 43 can be varied to achieve the desired mixing and
combustion sequence.
Toward prompting the mixin~ and combustion of the
fuel-air charge, opening 43 is provided with upper and
lower edges 46 and 47 respectively. The latter as shown
are rather abrupt to define an upright wall~which guides
the passage of combustion gases from cavity 38.
Operationally, during the piston compression stroke,
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the latter approaches top dead center with both intake 32
and exhaust valves 32a closed. This compression of the
~ previously introduced swirling air, drives much of said
air mass into cavity 38 thereby greatly increasing its
swirling veloaity.
ImmediateIy be~ore, and subsequent to reaching
the top dead center position a predetermined amount af fuel
is introduced ~rom injector 33 into the cavity 38 in a
di~ection aompatible with the direction of swirl within the
aylinder. As mentioned, this incoming fuel will form a
; ~ looalized relatively rich fuel-air mixture, which is readily
ignited as the mixture pas~es the spark plug 37, which at
this point of the stroke is energized.
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Thereafter during the power stroke piston ~3 will
recede from its top dead center position as the flame
circulates about annular passage 44. This simultaneously
permits the portion of the hot expanding gases and air
within cavity 38 to be discharged therefrom onto the
expanding combustion chamber 40. The advancing flame front
will continue to flow around cavity 38, combustion being
maintained by the remaining mixture in said cavity as well
as the free air that is still flowing therethrough. The
overall effect is that the inflamed mixture will move through
opening 43 in a manner to promote more complete mixing of
fuel, the products of combustion, and free air within
chamber 40.
The result will be a more rapid and uniform .
combustion event and consequently a more economical and
: : clear operation.
: Other modifications and variations of the invention :`
as~hereinbefore set forth may be made without departing from :
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. ~ the spirit and scope thereof, and therefore, only such limita- .
tions should be imposed as are indicated in the appended
claims. : ~ :
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