CA1067357A - Piston structure with cavity - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Piston structure for an internal combustion engine which includes a fuel injection system, the piston including an annular passage formed therein and having a restricted access opening communicating with said passage. The access opening is positioned to receive air as well as fuel, and to circulate products of combustion into the cylinder com-bustion chamber.

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Description

~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 .. . .
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 , 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 :::
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 , 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, : ..
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 ~ . . .. : .
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 , , : : .

~7357 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 .
flow restriction lies in a plane substantially normal to the cavity central axis. Thus, as the piston retreats from .
.. , ~ , ~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.
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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 .:
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 ~ . -fuel p~mp 12 whereby to vary the amount of fuel introduced to~each~cylinder to mix with incoming air. Fuel quantity :~ - .
is regulated in accordance with the engine load and speed.

Air is generally lntroduced to the cylinder through :~ ' : ,' .: , . . ' ' .

,: '.: ';~: ' , . . . " ' ''. , ' ' ' '; . "'" ',, ' ', ' ,, :' , , ' : . ' ' , ~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 ,: :
gasket 29 and a head 31. Each cylinder 21 as shown in ~ , ' 'j `-,: ' " .
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~067357 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.

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- 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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1()~7357 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 .
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 :` :
con~equently will be confined within the three sided passage 44.

Referring to Figure 1, on the power stroke piston -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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~ 73~i7 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 ;.- ,.... .,, .. ~
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 ~ -,- .
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, , 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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. ~L067357 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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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an internal combustion engine having at least one cylinder, a cylinder head, and a piston slidably arranged for reciprocatory motion therein, said piston including a face disposed to form with the cylinder head an expandable combustion chamber, valve means in said cylinder head being operable to selectively communicate with said cylinder to introduce a stream of air into the latter to form an air mass which is guided by the cylinder walls into a swirling path, means forming an annular chamber within said piston, and being formed with a substantially cylindrical wall, having a substantially flat lower surface, which Joins said cylindrical wall in a non-curved juncture, means forming a restricted access opening in said cylinder face affording access of air and fuel charge into said annular chamber, and for passing hot combustion gases therefrom, said means forming a restricted access opening being defined by a lip which overhangs the annular chamber, said means forming said restricted opening being further disposed eccentrically to said piston, and having a portion of the periphery of said opening disposed adjacent to said chamber cylindrical wall whereby to define an annular passage for guiding gas, which passage is progressively increased in cross sectional area for the first half thereof to confine said gas, and which passage progressively decreases in cross sectional area during the second half thereof to permit passage of gas therefrom and into expandable combustion chamber.