CA1162149A - Fuel porting for two cycle internal combustion engine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Two-cycle internal combustion engines are dis-closed incorporating intake and transfer ports and passages, and including passage means in the cylinder wall intercon-necting the intake tract and a transfer passage in a region above the piston when the piston is in bottom dead center position.

Description

FUEL PORTING ~OR TWO CYCLE
I~TERNAL COMBUSTIO~ ENGINE

BACKGROUND OF THE INVENTION:

Two cycle internal combustion engines are commonly provided with transfer passages and porting providing for delivery of fuel from the crankcase into the combustion chamber above the piston. Intake porting is provided in order to intro~uce fuel into the crankcase space for compres-sion therein upon the downward stroke of the piston and for delivery from the crankcase space through the transfer passage means. Intake valves are commonly provided in the intake passageway or intake tract.

The present invention is concerned with improve-ments in passage and porting arrangements both in the trans-fer and in the intalce systems providing foe inceease in delivery of fuel into ~he combustion chamber above the pis-ton. The increase in fuel delivery and the consequent im-provement in operation of the engine are accomplished accord-ing to the present invention by providing a novel inter-relationship between the intake porting and passages and the transfer porting and passages, according to which the intake porting and passages not only deliver the fuel to the crankcase space, but also deliYer fuel by an injector type of action into the transfer fuel flow during the phase of the cycle of operation in which fuel is being transferred from the crankcase to the combustion chamber.

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In the arrangements according to the present in-vention, reed type intake valves are preferably provided in the intake tract, and injector porting or passages are provided ir. order to deliver fuel from the intake tract substantially directly into the transfer passage means.
According to the invention, this may be accomplished in several ways by providing a region of at least one transfer passage intermediate its ends in communication with tne intake passage or tract downstream of the valve means.
Indeed, in certain arrangements according to the invention, a region of the intake tract downstream of the valve means and a region of at least one transfer passage intermediate its ends are common to each other.

Still further, according to the invention provi-sion is made for increased fuel input by the employment o a novel form of passage means interconnectiny the intake tract and the transfer passayes and ports close to the point of fuel delivery into the cylinder. Moreover, this is ac-complished in accordance with the present invention in a manner which not only increases the intake of fuel but which also enhances the scavenging of the combustion gases from the cylinder un~er the influence of the incominy fuel.

Several embodiments of engines providing improved operation in various aspects as referred to above are il-lustrated in the accompanying drawings and described here-inafter.

BRIEr D~SC:R-PIION ~ LRAWINGS:

Figure 1 is a view in section, taken along the line 1-1 of Figure 2, and illustrating a two cycle reed valve engine having intake and injector porting according to one embodiment also disclosed in my USA Patent #4,202,~98, issued May 13, 1980.

Figure 2 is a sectional view taken along the line

2-2 of Figure l;

Figures 3 and 4 are views similar to Figures 1 and 2, and illustrating an embodiment of one engine similar to that of Figures 1 and 2, but incorporating a novel arrange-ment of portin~ and passages hereinafter fully described.

I~ETP~ILED DESCRIP'rION:

Figures 1 and 2:

Before considering the drawings in detail, it is first pointed out that Figures 1 and 2 are respectively the same as Figures 5 and 6 of my prior USA Patent ~4,202,298, identified above. Significant parts of tbe apparatus shown in these figures are described herebelow, and certain portions ~ of this description correspond to portions appearing in said prior USA patent where the structural features are the same. It is to be noted, however, that in Figure 2 there is included a diagrammatic illustration of certain operating conditions which (while they would occur in the engine as shown in the prior patent; are not illustrated therein.

In Figures 1 and 2, there is shown a somewhat diagrammatic representation of a two-cycle engine comprised of a housing 10 the upper portion of which defines a cylin-der llC and the lower portion of which defines a crankcase 12. The upper, annular portion of the crankcase interfits with cylinder liner structure 13C, which extends throughout the height o.f the cylinder llC, except where omitted or ~emoved to provide certain porting (including the usual exhaust port 39), and projects beneath it in the manner plain from Figure 1. While the use of a liner is pre~erred, it is not essential, and for most purposes of the present invention, the liner can be considered as a part of the cylinder llC, which, in turn, forms the upper portion of housing 10. A piston 14C is mounted foe reciprocation within the cylinder and its connecting rod lS is eccentri-cally mounted upon the crankshaft within the lower portion 16 of the crankcase, as indicated at 17. As is convention-al, a circular counterweight is preferably employed, as shown at 18.

The cylinder llC includes transfer passages l9C, two being provided at each side of the cylinder in this embodiment, the lower end of each of which is in open com-munication with the crankcase and the upyer end of each ~1~6~
of which terminates in a transfer port, one of which is indicated at 21C and another of which is indicated at 36C.
A similar pair is provided at the opposite side of the cyl-inder. The transfer ports are exposed in the cylinder S above the piston when the piston i5 in bottom dead center position. Conveniently, and as shown, the passages l9C
are provided in the wall of cylinder llC, lying behind the liner 13C, which is apertured to provide the lower communi-cation at 20 as well as the upper ports 21C and 36C. As is conventional, combustible gases inletted during the up-ward stroke are pressurized beneath the piston and in the crankcase by the piston throughout its downward stroke toward the bottom dead center position illustrated, and the gases flow from the crankcase through openings 20, pas-sages l9C and ports 21C and 36C, from whence the gases enter the cylinder above the piston 14C.

The cylinder llC also includes an intake chamber 22 which leads to a source of fuel (not illustrated) and which chamber conta.ins the reed valve means 23, which is adapted to open and provide for intake of fuel throughout the entire upward stroke of the piston, and to close, during the downward stroke of the piston, when the fuel inletted into the space below the piston is being compressed. While, for certain purposes of the present invention, the reed valve means 23 may take a variety of forms known in the art, it is preferred that said reed valve means be of the ~2~

so-called "ven'ed" type desr~ibed in my earlier USA patent No. 3,904,340. It is also preferred that the valve means includes a plurality of valve assemblies as described here-inafter.

In the embodiment illustrated in Figures 1 and 2, the reed valve means 23 includes a reed valve body or cage of wedge shape, with the base end of the wedge interior-ly open to the fuel supply passage, each inwardly inclined surface of the wedge-shaped cage having a pair of valve ports and each such port provided with primary and secondary reeds 24 and 25, the primary reeds being vented. This valving arrangement is more fully illustrated and described in my USA Patent No. 3,905,340 above identified. The opposite sides or ends (top and bottom) of the reed valve cage are provided with parallel triangular walls.
.. . . . .
From Figure 2, it will be seen that the embodi-ment of Figures 1 and 2 includes two valve assemblies 23 arranged in side-by-side relation and positioned respec-tively in separate intake passages 27C,27C lying at opposite ZO sides of the dividing wall 28C. The fuel entering through the valves 24, 25 flows directly into the cylinder intake passages 29C and also laterally and downwardly into addi-tional intake passages to be described.

It is desirable~ as shown in Figures 1 and 2, that each reed caye be positioned with its apex extended in a vertical direction, i.e., in a direction parallelling the axis of the cylinder. When positioned in the manner S just referred to, it will be clear from inspection of Figure 2 that the flow of fuel through the valve por~s controlled by the reed valves or petals 24 and 25, substantially di-rectly enters the passages downstream of the valves, without the necessity for any extensive or sharp angular deflection.
These and other factors are of importance in maximizing the input of fuel into the engine.

The above mentioned directness of flow is enhanced by virtue of the arrangement as shown in which a pair of reed valve assemblies are mounted in separate generally lS parallel intake passages 27C,27C, as established by inter-` vening wall structure including partition 28C.

It will be seen from inspection of Figures 1 and 2 that the areangement here shown not only includes two transfer passages l9c at each side of the cylinder, but also includes a combined intalce and transfer passage at each side. The combined intake and transfer passages are described below but it is first pointed out that the trans-fer passages are provided with appropriate ports into the combustion space and also have their lower ends communi-cating with a chamber 41 formed within the upper portion J~

12 of the engine housing lO, this chamber also communicating with the lower portion of the crankcase but being located above the crank and counterweight space immediately adjacent to the lo~er ends of the transfer passages.

As seen in Figures 1 and 2, the intake passages or tracts 29c downstream of the reed valves 23 have com-munication with the chamber 41 and the crankcase space; and this cornmunication is arranged within the wall structure 42 in such manner as to remain open throughout~the entire cycle of operation of the engine, including bottom dead center position of the piston. The intake passages or tracts 29c also extend upwardly for communication with the cylinder ports 43, one such port being provided for each of the pas-sages 2gc. These ports 43 are preferably positioned at sub-stantially the same level in the cylinder as the ports 21c and 36c of the transfer passages 19c, and the ports 43 serve a similar function, but also directly communicate with the intake system just downstream of the valves. It will be observed that the intake passages 29c receive fuel from the valves 23 in a region above the chamber 41 and intermediate the ports 43 and the zone in which the passages 29c communi-cate with chamber 41 and the crankcase. Therefore, during the lower portion oE the downward or compression stroke of the piston, the intake passages 29c serve to deliver corn-pressed fuel from the chamber 41 and thus from the crank-case upwardly into the combustion chamber, in the general manner of a transfer passage, but since these passages 29c have communication with the fuel supply, at least at higher speeds of operation, additional fuel is supplied to the flow by virtue of '!injector" action, which is referred to in various of my prior USA patents, including the two USA patents above identified.

It is also to be noted that since the chamber 41 in the immediate vicinity of the lower ends of the trans-fer passage l9c directly communicates with the intake pas-sages or tracts 29c, under certain conditions of operation, the delivery of fuel into the combustion space through the transfer passages l9c is also augmented.

It will be noted that in effect at least a region of each passage 29c serves in part as an intake tract and .. . .
in part as a transfer passage.

Figures 3 and 4:

The embodiment shown in Figures 3 and 4 incor-porates most of the structure described above in connection with Figures 1 and 2, but in addition the embodiment of Figures 3 and 4 includes some additional passage means pro-viding intercommunication between the intake tract and one of the transfer passages at each side of the cylinder.
Thus, comparison of Figure 4 with Figure 2 will show that 21~3 a passage ~4 is provided in Figure 4 at each side of the cylinder between the intake/transfer passagé 29C and the adjacent transfer passage 19C; whereas in Figure 2, these two passages are separated by an intervening wall.

Attention is also called to the fact that Figure 4 is taken on a section line 4-4 applied to Figure 3 which section line is somewhat higher than the top of the piston in bottom dead center position. It will thus be seen that the passage means 44 interconnects the fuel supply and the adjacent transfer pas~age in a region above the piston when the piston is in bottom dead center posiiion; i.e., in the region immediately adjacent to the pair of cylinder ports 36C - 43 at each side.

In the embodiment of Figures 3 and 4, therefore, the intercommunication between the fuel supply and a trans-fer passage at each side of the cylinder is not only pro-vided in a region neae the lower ends oE the transEer pas-sages, but also near the upper ends thereof; and as will be explained hereinafter, this latter zone of intercommuni-cation between the intake and the transfer system is of benefit not only in increasing the fuel intake capability, but also in improving the scavenging action by which the exhaust gases are discharged through the exhaust port 39 under the influence of the incoming fuel.

The structural embodiment shown in Figures 1 and ~ is identical to that shown in Figures 5 and 6 of USA Patent #4,202,29~; and the structural embodiment of Figures 3 and 4 is the same except for the additional passage means described above.

CONC~USION:

Both of the embodiments shown in the drawings and described above include intake tracts or passages from .. . . . . . . . .
the fuel supply and valve cages in constant communication with the crankcase space or chamber in a region below the piston throughout the entire cycle of operation of the en-gine including the bottom dead center position. Thls com-munication is maintained at normal operating speeds with-out requiring reversal of flow through the transfer pas-sages; and as brought out in certain of my USA patents above identified, this is of importance in augmenting fuel input to the combustion chamber. It will further be seen that in both embodiments, a chamber 41 is provided below the piston and above the crank and counterweight space in the crankcase, with which chamber not only the intake tract communicates but with which the inlet end of the transfer passages also communicate. This chamber is partially sepa-rated from the crank and counterweight space in the crank-case by the configuration of the wall structure of the engine housing. The intercommunicating opening between the chamber and the crank and counterweight space in the crankcase is, of course, adequate to accommodate the connecting rod 15 and its motions, but, particularly at high engine speeds, the crank and counterweight space is in effect a "dead"
space and the chamber 41 is a "live" and very active space, through which fuel passes at high rate from the intake side - of the system to the transfer side of the system, and thus to the combustion chamber. This fuel flow occurs at high .
engine-speeds in a manner which is not substantially influ- -enced by the fact that the chamber 41 is in communication with the crank and counterweight space. One of the reasons why this flow is not substantially influenced by the COIO-munication between the chamber and the crank and counter-weight space is the fact that the chamber is immediately adjacent to the piston whereas the crank and counterweight .. . .
space is remote from the piston and it is the piston motion which acts to reduce and increase the pressure in the cham-ber, as occurs on the suction and compression strokes of the piston. This action of the piston originates ilNmediately under the piston and is, thereore, highly effective in pro-viding the desired pressure fluctuations in the chamber;
and at high speeds, such fluctuations are not communicated to any substantial extent downwardly to the more remote space where the crank and counterweight are enclosed in the engine housing, provided that the intake porting is located at least as high as this chamber 41.

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As to most of the fuel flow passages, it is also of importance that complete reversal of the direction of flow is not required, as such reversal, particularly at high engine speeds, has a tendency to diminish delivery ~f fuel, because of the inertia of the fuel itself. Even in the case of the intake passages 29C, at normal ope~ating speeds, the fuel flow through the passages 29C is in the upward direc-tion throughout the cylce of operativn and this is of impor-tance in maintaining high velocity of flow and thereby pro-vide the fuel injector effect contemplated according to the invention.

In both of the embodiments illustrated and des-cribed, the supply of fuel to the combustion space by virtue of transfer flow of the fuel from the compression side of lS the piston to the combustion side of the piston is augmented by an injector or induction type of action resulting in flow of some fuel from the intake or supply passages substantially directly into the transfer flow without previous compression in the space below the piston. This action is of appreciable 2~ efEect over a substantial range of engine speeds and is par-ticularly significant at high engine speeds, and this is particularly true of the intake/transfer passages 29C.

In further explanation of the significant ~iffer-ences in the functions of the arrangement of Figures 3 and ~5 ~ as compared with the arrangement of Figures 1 and 2, atten-tion is now directed to the diagrammatic representation in Figure 2 of the pressure condition in the cylinder above the piston during the inletting of fuel and the scavenging of exhaust gases. The line marked P in Figure 2 which is extended across the cylinder, schematically represents the zero pressure line in the cylinder above the piston during the inletting of fuel through the ports 21C, 36C and 43.
By zero pressure condition is here meant a pressure equal to the ambient or atmospheric pressure, and the fluctuations - above and below that value as referred to hereinafter are of course values above and below atmospheric pressure.
Similarly, the line P and the f-luctuations described with relation to that line may also be understood as velocity fluctuations, i.e., fluctuations in the velocity of the fuel entering the cylinder at the right side and proceeding to the left. Actually the flow is upwardly directed from the ports 21Cr 36C and 43 and thence laterally and down-wardly, but the line P represents the æero condition in a plane intermediate tbe piston and the top of the cylinder.
The line P not only represents zero velocity, but also zero pressure, as explained above.

It will be noted that to the right o~ the line P stippling has been applied within the area of the cylin-der, with an increase in the density of the stippling as the cylinder wall is approached at the intake side of the of the engine. This variation in the density of the stip-pling indicates that in consequence of the input of fuel when the piston is near bottom dead center position, the velocity and pressure is greater adjacent the irltake side and diminishes as the line P is approached. To the left of the line P the pressure and velocity would normally be somewhat lower than the zero value referred to.

FrQm the above, it will be seen that in the embodi-ment as illustrated in Figures 1 and 2 the fuel intake in conse~uence of the porting and passage arrangements is in-. .
creased and in addition this increase fa~orably influences the scavenging action. However, as explained herebelow, the modification incorporated in the embodiment shown in Figures 3 and ~ still further enhances not only the fuel intake but also the scavenging action of the incoming fuel.
It will be observed from E'igure 4 that the pressure or velo-lS city line P is indicated in three different positions at Pl, P2 and P3, representlng typical "Low", "Mid-range", and "High-range" RP~ rates. It will be understood that the stippled area to the right of the pressure line Pl in Figure 4 would be of progressively greater area with in-crease in speed, as is indicated by the positions of the lines P2 and P3. This is a point of significant difference between the embodiment of Figures 3 and 4 on the one hand and the embodiment of Figures 1 and 2 on the other hand.
With the porting and passage arrangemellt of Figures 1 and 2, the location of the zero velocity or pressure line P

2~
remains relatively constant througho~t the speed of the engine; and in addition the stippled area to the right of the pressure llne P in Figure 2, as already mentioned, in-creases substantially in density (i.e. the pressure and velocity increases) as the cylinder wall adjacent the in-take side is approached.

The arrangement of Figures 3 and 4 has two dif-ferences as compared with the arrangement of Figures 1 and 2. In the first place, there is a much greater variation in the location of the zero line depending upon the speed of operation of the engine, the pressure line progressively approaching the exhaust side of the cylinder as the engine speed is increased. Moreover, while there is more variation in the density of the stippling to the right of the line Pl in Figure 4, the variation is not as great as it is with the embodiment of Figures 1 and 2.

The foregoing differences between the embodiment of Figures 3 and 4 as compared with the embodirnent of Fig-ures 1 and 2 result from the fact that with the additional passa~e means 44 interconnecting the intake/transfer pas-sages 29C with the adjacent transfer passages l9C occurs principally above the level of the piston in bottom dead center position, with consequent increase in direct fuel flow from the intake system into the space immediately above the piston.

The arrangement of Figures 3 and 4 therefore, not only incre~ses the overall fuel intake but also enhances the scavenging action especially at high engine speeds, . which occur-s when the piston descends an~ uncover.s th~ ports - 21C, 36C and 43, there being a set of these three ports at each side of the cylinder, as will be apparent from examination of Figures 3 and 4.

In connection with the references herein to the . . .. . . .. . .
crankcase and the cylinder, and to the location of various-. ports and passages, it shauld be kept in mind that a portion of what is functionally the wall of the cylinder i5 often (~or instance as shown in the drawings) actually located within the confines o~ the metal of the crankcase casting.

Moreover, various of the ports and passages pro-. 15 vided in two-cycle engines, including intake porting and passages and transfer porting and passages, are quite oten extended from a region lying within the metal of the cyl-inder casting into a region lying within the metal of the crankcase casting, or vice versa. From the standpoint of the operation and functioning of the various ports and pas-sages, and the opeeation and unctioning of the engines as a whole, it is not significant just where the parting line occurs separating the metal of the "cylinder" from the metal of the "crankcase", nor is it of any significance just which part of the metal of which part of the engine is traversed by some particular passage.

Claims (6)

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

1. A variable speed, two-cycle, internal com-bustion engine comprising a crankcase and a cylinder having a combustion chamber, a piston working in the cylinder, the piston and cylinder being located and proportioned to provide a fuel chamber below the piston but above the crank space in the crankcase, port means in the cylinder including intake porting and passage means providing communication with said fuel chamber, an intake tract in fluid communi-cation with the intake porting, reed valve means disposed in the intake tract and located in a position confronting the bottom dead center position of the piston for control-ling the flow of fluid through the intake tract, the port means further including transfer porting communicating with the combustion chamber above the piston when the piston is in bottom dead center position, and a transfer passage formed in the cylinder and one end of which communicates with the transfer porting and the other end of which communi-cates with said fuel chamber for conveying fluid from the fuel chamber to the transfer porting, and the transfer pas-sage being in communication with the intake tract downstream of the valve means and providing for flow of fluid from the intake tract directly into the transfer passage, the communication of the transfer passage and the intake tract including fuel flow passage means in the cylinder wall inter-connecting the intake tract and the transfer passage in a region above the piston when the piston is in bottom dead center position.

2. An engine as defined in Claim 1 and further including passage means interconnecting the intake tract and said fuel flow space throughout the entire cycle of the engine.

3. An engine as defined in Claim 1 and further including passage means interconnecting the intake tract and the transfer passage in a region below the top of the piston when the piston is in bottom dead center position.

4. A variable speed, two-cycle, internal com-bustion engine comprising a crankcase and a cylinder having a combustion chamber, a piston working in the cylinder, a fuel chamber below the piston, port means in the cylinder including intake porting and passage means providing com-munication with said fuel chamber and further including a fuel supply port in the cylinder wall above the piston in bottom dead center position, an intake tract in fluid communication with said port and with said intake porting, reed valve means disposed in the intake tract for controll-ing the flow of fluid through the intake tract, the port means further including transfer porting communicating with the combustion chamber above the piston when the piston is in bottom dead center position in a region adjacent to said fuel supply port, a transfer passage formed in the cylinder and one end of which communicates with the transfer porting and the other end of which communicates with said fuel chamber for conveying fluid from the fuel chamber to the transfer porting, and fuel flow passage means inter-connecting the intake tract and the transfer passage in the region of said fuel supply port above the piston when the piston is in bottom dead center position.

5. A variable speed, two-cycle, internal com-bustion engine comprising a crankcase and a cylinder having a combustion chamber, a piston working in the cylinder, a fuel chamber below the piston, port means providing com-munication with said fuel chamber, an intake tract in fluid communication with said port means, reed valve means dis-posed in the intake tract for controlling the flow of fluid through the intake tract, at least two transfer ports com-municating with the combustion chamber above the piston when the piston is in bottom dead center position, transfer passages formed in the cylinder and respectively communi-cating with the transfer ports and with said fuel chamber for conveying fluid from the fuel chamber to the transfer ports, and fuel flow passage means interconnecting the trans-fer passages in a region above the piston when the piston is in bottom dead center position.

6. A variable speed, two-cycle crankcase compres-sion, internal combustion engine, comprising: engine housing structure including a cylinder and a crankcase, a piston mounted for reciprocation in the cylinder between top and bottom dead center positions, at least one transfer passage in the engine housing structure having an opening in communi-cation with the crankcase and having an opening in communi-cation with the cylinder above the piston in bottom dead center position, a fuel intake chamber for receiving fuel from a supply source, reed valve means for controlling the flow of fluid through the intake chamber substantially radially of the cylinder in the region of the bottom dead center position of the piston, and passage means formed in the engine housing structure and communicating with the intake chamber downstream of the reed valve means, the passage means including intake porting in the cylinder wall in the bottom dead center position of the piston and providing for substantially direct flow of fuel from the reed valve means into the space below the level of the lower edge of the piston at the side presented toward the porting when the piston rises substantially above the bottom dead center position, the passage means including portions communicat-ing with the intake chamber and with the transfer passage in a region closely adjacent to the opening communicating with the crankcase and also in a region closely adjacent to the opening communicating with the cylinder, and the pas-sage means further including a transfer passage communicat-ing with the intake chamber in a position in radial alignment with the reed valve means and also communicating with the cylinder above the piston and with the crankcase.