US3182643A - Two stroke cycle crankcase scavenged internal combustion engine - Google Patents

Description

May 11, 1965 w. TENNEY 3,182,643

TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE Filed April 9, less 4 Sheets-Sheet 1 FIG. 1

INVENTOR. Mum/w A. Tan/mar Irma-vars May 11, 1965 w. L. TENNEY 3,182,643

. TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE INVENTOR. I Mann 1. fimvey firrokmm May 11, 1965 w. L. TENNEY 3,182,643 TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE Filed April 9, 1963 4 Sheets-Sheet s FIG. E

INVENTOR Alla/AM 1.. firm/7 Arnzuey;

y 1965 w. L. TENNEY 3,182,643

TWO STROKE CYCLE CRANKCASE SCAVENGED INTERNAL COMBUSTION ENGINE Filed April 9, 1963 4 Sheets-Sheet 4 FILE.

lllllll'" .llllll' INVENTbR [Wu MM 4. 724M157 Jrromwsr:

United States Patent 3,182,643 TWO STROKE CYCLE CRANKCAS'E SCAVENGED INTERNAL COMBUSTION ENGINE William L. Tenney, Crystal Bay, Minn. Filed Apr. 9, 1963, Ser. No. 271,727 11 Claims. (Cl. 123-51) This invention relates to two stroke cycle crankcase scavenged internal combustion engines of improved design. engine.

It is known that four-cycle engines may be made to develop peak horse power at a piston speed of about 4000 feet per minute, and materials and mechanical designs are available which permit operation at such speeds. By contrast, the usual loop-scavenged two-cycle engines develop peak horse power at piston speeds of about 2000 feet per minute. Heretofore there has been no design available in the art of two-cycle engines permitting the peak horse power to be attained at piston speeds in the 4000 feet per minute range.

I have discovered certain improvements in the field of two-cycle engines, whereby such engines will develop peak horse power at piston speeds of 4000 feet per minute or thereabouts, and it is therefore an object of the invention to provide such improved two-cycle crank casescavenged internal combustion engines capable of developing maximum horse power at or about 4000 feet per minute piston speed.

Here-tofore the fuel mixture scavengedtwo-cycle loopscavenged internal combustion engines utilizing known design techniques, have yielded a specific fuel consumption of approximately twice as greatas comparable four-cycle engines. Consequently the use of large horse power fuel mixture scavenged two-cycle loop-scavenged engines has been restricted due to their very large tuel; requirement. By contrast the four-cycle engines have had a much better (lower) specific fuel consumption, but even though capable of operating at higher piston speeds, such engines are generally heavier and bulkier than two-cycle engines of the same horse power.

It is an object of the present invention to provide an improved two-cycle cranckcase scavenged internal combustion engine having a specific fuel consumption comparable with that of founcycle engines of equal displacement, while at the same time having horse power output for a given cylinder size far greater than that of either the four-cycle over-head valve engines or of the two-cycle loop-scavenged engine.

In two-cycle crankcase scavenged internal combustion engines the ratio of the air pumped from the crankcase to the total volume of the cylinder is known as the delivery ratio (sometimes also called the scavenging ratio). It is an object of thepresent invention to provide a reduced delivery ratio, so that the engine works further down on the curve of delivery ratio, with resultant improved fresh charge trapping efiiciency and specific fuel consumption.

According the Hans List as reported in scavenging of Two Stroke Cycle Diesel Engines by Svveitzer, page 45 in a uniflow scavenged engine the fresh charge trapping efficiency can be virtually 100% up to a scavenging ratio of approximately 60% 70%. It is an object of the present invention to provide a two-stroke cycle, crankcase scavenged internal combustion engine wherein a uniflow scavenging pattern is provided and which operates at or near the 60%70% ratio atfull throttle, with resultant reduction in the full throttle specific fuel consumption to approximately half thatof prior loop-scavenged two-cycle engines and with specific consumption approximately equal to that of four-cycle engines of equivalent cylinder size.

It is an object of the invention to provide such "ice In loop-scavenged two-cycle engines all the ports are arranged around the cylinder at substantially the same level, so as to be uncovered by'the piston as it proceeds towards its lowermost position, the ports on one side of the cylinder generally being devoted to induction and on the other side being generally devoted to exhaust of the burned gases. The height of the ports as a percentage of piston travel is limited. Accordingly, in such loopscavenged engines, there is in effect an insufiiciency of piston-stroked cylinder wall area that can bedevoted to porting the cylinder. The net efiect, has been that even though higher piston speeds can be mechanically very high, and the power delivery curve may be made cor respondingly flatter and fatter, without reliance much upon pulsations (resonance) in exhaust components for increasing the horsepower at certain speeds.

It is another object of the invention to provide an improved two-cycle engine wherein the exhaust valving is accomplished by separate pistons reciprocating generally in opposite phase to the main piston with the ancillary result that such engines may be dynamically balanced advantageously by properly weighing such separate pistons in respect to the main piston.

It is an "object of the invention to provide improved mechanical designs utilizable in internal combustion engines of the carburetor offuel injection spark ignition type and diesel 'types utilizing self ignition or spark ignition.

Otherand further objects are those inherent in the invention herein illustrated, described and claimed and will be apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

The invention is illustrated with reference to the drawings wherein:

FIGURE 1 is a transverse sectional view of one form of engine embodying the present invention;

FIGURE 2 is a transverse sectional view through a modified form of engine embodying the present invention; p 1

FIGURE 3 is a transverse sectional view through another modified form of engine embodying the persent invention; V l i a FIGURE 4 is aside elevational view taken in the direction of arrows 4-4 of. FIGURE 3; 7

FIGURE 5 is a transverse sectional view taken along the lines and in the direction of arrows 5-5 of FIG, URE 3;

FIGURE 6 is aside elevational view similar to FIG- URE 4 showing: a slightly modified form of engine embodying the invention; and

FIGURE 7 is a transverse sectional view taken in the direction of arrows 7-7 of FIGURE 6. r

Throughout the drawings corresponding numerals refer to the same parts. i

Referring to FIGURE 1 there is illustrated an internal combustion engine embodying the present invention. This engine utilizes a main crankcase generally designated and cylinder generally designated 11, attached thereto. The crankcase 10 is split as, for example, at the flanges 12 so that it may be opened. Any style of crankcase construction may be used.

The cylinder generally designated 11 begins at the lower edge 11A and has a main cylinder portion beginning at 11A and continuing to junction 4444. The cylinder 11 thence continues upwardly through a supplemental (or exhaust) cylinder portion 11D to upper termination 11E. In the form of engine shown in FIG- URE 1, the cylinder is of the same diameter throughout the full length of portions 11C and 11D.

Part way up the cylinder from the bottom there are provided a plurality of induction ports 14 which are spaced around the cylinder. The dimensions of these ports, the number and size of lands between them, and direction of induction through such ports may be varied according to good design practice. These ports 14 form the upper termination of a transfer passage 15 which entirely encircles the cylinder 11 at and to some extent below the ports, it being noted that portion 11C of the cylinder forms the inner wall of the transfer passage 15 whereas the outer wall of such passage is formed by the shell 16. The shell curves inwardly at 16A and joins the cylinder wall at 16B. The transfer passage 15 is provided with ports 17 leading into the interior 10A of the crankcase 10.

Opposite the bracket 18 there is illustrated an induction port for the crankcase 10. One or more of these ports 18, suitable for handling the volume of air or airfuel carbureted mixture, may be provided asentrances into the crankcase 10. Only one such port is illustrated here, so as to simplify the drawings, it being understood that the size and/or number of such ports entering the crankcase is chosen suitably for the volume of gases requiring inlet into the crankcase. Each induction port (or ports) 18 is provided with a check valve to prevent the outflow of gases from the crankcase 10. In the present instance this is illustrated as composed of valve leaves 19 attached at 20 to the body of the induction port 18 and are sized so as to rest against an integral streamlined land 21 in the passage through port 18. Gases may flow through the induction port in the direction of arrow 22, but outflow of these gases is restrained by the valve leaves 19. Any suitable valve may be used in the induction port such as the poppet valve, rotary valve, etc.

The crankcase 10 serves to support rotatably a crankshaft 25, which in the crankcase is provided with one (or two spaced) crank wheels 26, serving to support crank pin 27 on which the lower end of the connecting rod 28 is journalled. In the illustration in FIGURE 1 there is shown a single crank wheel 26 having an overhanging crank pin 27. Consequently, with such design, the connecting rod 28 need not be split at its lower end for assembly. A usual connecting rod bearing, not illustrated, is of course, included. The upper end of the connecting rod 28 is journalled by means of a piston pin 29 to the piston 30 which is provided with two or more piston rings 31. The piston has a dome shaped top, and the height of the piston is adjusted in relation to the height of the ports 14, so that the upper edge of the piston will uncover the full posts 14 when the piston 30 is in the lower position, as shown in full lines in FIGURE 1. As the piston travels upwardly it covers the ports 14. The upper position of the piston 30 is shown in dotted lines in FIG- URE 1. V

The cylinder 11, as previously noted, continues directly upwardly with the same diameter and at its upper end 11E may be provided with a second crankcrase generally designated 32 which is similarly split at the flanges 34 to permit assembly. No crank case closure is actually required since piston 42 is not required to do any pumping but a crankcase or at least a cover is desirable to keep out dirt and dust and enclose lubricants for the upper moving parts (piston 42, pin 41, connecting rod 38, crankpin 37, crankshaft 35). This crankcase 32 provides support for crankshaft 35 having one (or two spaced) crank wheels (cheeks) 36 which support a crankpin 37 on which there is journalled the crank end of a connecting rod 38. In this illustration there is shown one such crank wheel 36 with an overhanging (stub) crankpin 37 and the connecting rod 38 is not split to receive a bearing at the crankpin end. It will be noted that the crankpin 37 is displaced angularly A in advance of the POSI- tion of the related crankpin 27, it being noted that rotation is in the direction of arrow 39. The amount of this angular displacement may be varied, 10 being typ1cal.

In the upper portion of the cylinder 11 there are a plurality of exhaust ports 40. These ports are preferably of equal size and uniformly spaced around the cylinder 11. The size of these ports 40, is made in accordance with good design, dependent upon valve timing and gas flow requirements.

The connecting rod 38 is journalled by means of a pin 41 to a piston 42 which is thereby operated up and down in the cylinder 11. Piston 42 is provided with two or more piston rings 44. The vertical height of the piston 42 is such that in relation to ports 40, when the piston is in its uppermost position in the cylinder, as shown in FIGURE 1, it will completely uncover the exhaust ports 40. It will be noted that the piston 42, as shown in FIG- URE 1, is beginning its downward travel, hence its lower edge is very slightly below the upper edges of the ports 40. In its lower position, shown in dotted lines in FIG- URE 1, ports 40* are entirely closed.

A suitable manifold (not shown) is provided around the cylinder 11, and connected to the exhaust ports 40.

The piston 42 has a slightly dome shaped top and in its lowermost position is shown in dotted lines. When the pistons 30 and 40 are closest together, as shown in dotted lines in FIGURE 1, the upper curved dome portion of piston 30 and the corresponding lower curved dome portion of piston 42 are close together but they do not engage each other. In this position the pistons will have compressed between them the induced charge and the compression is at maximum at this point. The movement of both pistons contribute to compression of the charge in the cylinder. The point of maximum compression is shown in FIGURE 1, and the line 44 is halfway between the pistons when they are at such most proximate, maximum compression position. Around the wall of cylinder 11 at line 44-44 there are provided one or more bosses 45-45 in which there are threaded apertures 4646 to receive spark plugs or fuel injection nozzles, or both. The bosses are made sufficiently deep so that no portion of the spark plugs (or fuel injection nozzles) will protrude into the space between the pistons to cause interference.

In the engines of the present invention the two crankshafts 25 and 35 are arranged to be driven together and this may be accomplished by gearing or sprocket and belt or chain drives. For small engines a sprocket driven toothed belt operates satisfactorily. In other engines it may be desirable to provide a gear tower, metal chaintype belt or equivalent drive. In the form shown a toothed belt pulley suitable for a flexible toothed belt is provided at 47 on the crankshaft 28 and an identical toothed belt pulley of the same size is provided on the crank shaft 35. These are connected together by a toothed flexible belt 49 and consequently the crankshaft 28 and the crankshaft 35 are driven in synchronism with the position of crankpin 37 leading the position of crankpin 27 by the angle A".

The cylinder 11, in the exemplary engine shown in FIGURE 1, has a uniform diameter from bottom 11A to top 11B and the pistons 30 and 42 are of the same diameter. The displacement accountable to each of these pistons is accordingly the area of the piston multiplied by the piston movement of stroke. Piston movement is, in turn, determined by the radial positions of crankpins 27 and 37 on their respective crank wheels (crank cheeks). The displacement of the lower piston 30 is thus its area times the stroke of piston 30 in the cylinder. In this particular engine, which is merely one example of the invention, the stroke of piston 30 is made twice as much as the stroke of piston 42, i.e. the crank radius 27R is made twice as much as crank radius 37R.

According to this invention the piston which accomplishes the exhaust valving function at the exhaust end of the cylinder may be either one piston as shown in FIGURE 1, and FIGURE 2, or several pistons as shown in FIGURES 3, 4 and 6. According to this invention the total displacement of this exhaust valve piston (or pistons) accomplishing the exhaust valving function, is made from about to about 50% of the total displacement accountable to the main piston, and is preferably made %-30% of the displacement accountable to such main piston. Thus in FIGURE 1, the movement stroke of the main piston 42 in the cylinder portion 11C may be 50% to 10% of the movement stroke of the exhaust piston 30 in the cylinder portion 11D, since in this illustration, the two pistons are of the same area. The radial dimension 37R determines the movement of the piston 42, and this dimension is calculated according to the requirements of exhaust port area and timing.

An increase in the number of exhaust pistons relative to the intake piston permits a decrease in the total displacement of the exhaust pistons, for any given exhaust port timing and area. Also, a smaller diameter of the exhaust pistons than of the intake piston produces a more compact and more efficient combustion chamber, and permits a more favorable spark plug location.

The engine herein described may be either of the type having spark plugs and a carbureted air 'fuel mixture or may be of the diesel type. In respect to FIGURE 1, let it be assumed that the induction port (or ports) 18 are connected to a suitable carburetor, that spark plugs are pro vided for at the openings 46 and that a suitable exhaust manifold is connected to ports &0. Under such conditions, and the pistons approach the positions shown in dotted lines in FIGURE 1, the compression of the previously induced charge will occur, due to the combined movement of the two pistons 30 and 42. At a suitable time, in advance of reaching the point of maximum compression, ignition occurs at the spark plugs, and the firing of the thus compressed charge will occur. Both pistons reach positions shown in dotted lines, and thereafter move away from each other, it being noted that rotation is in the direction of arrow 39. Since piston 42 leads by some degrees (angle A) the movement of the piston 30, piston 42 will, at the end of the work stroke uncover the lower edges of the exhaust ports 40 and some outflow of exhaust gases will occur at the higher pressure then still maintained in the cylinder, thus initiating an upward flow and outflow through ports 40 of the spent charge within the cylinder. Also, the height of the ports 40 will generally be made such that they will open earlier than the ports 14, even if angle A is zero, or even negative. Meanwhile the downward movement of piston'30 is compressing the charge within the crankcase 10, outflow of such charge through the induction port 18 being restrained by the valves 19. As the upper edge of the piston 30 uncovers the upperedge's of the ports 14, such compressed charge within the crankcase 10 will flow through the transfer passages 15 and through the then opening ports 14. As this flow is desirably distributed generally uniformly around the cylinder it will move into the cylinder as shown by the arrows 50. If desired, the lands between the ports 14.1nay be suitably shaped and directed so as to provide any preferred or desired pattern of flow of induction, the desideratum being that the flow via arrows 50 should advance frontally and as nearly as possible as a plug of fresh charge which pushes upwardly before it the spent charge which is then outflowing through the ports 40. Port designs of many kinds are available which, cooperation with the shaping of the upper portion of the piston uncovering the induction ports, aid in approaching the ideal condition, and such designs may be utilized as desired, they being per se no part of the present invention.

It will be noted that the flow via arrows 50 is a uniflow pattern the spent charge always flowing upwardly and then outwardly through the ports 40, as indicated by the arrows 50 and 51.

It has been found that an engine, utilizing the design parameters of this invention, illustrated in FIGURE 1 and other embodiments to be described may have an almost perfect fresh charge trapping efficiency up to the scavenging ratio 60%70%, Likewise such engines may be operated with high torque at piston speeds of 3000 feet per minute and even up to 4000 feet per minute or more, due to the large relative cylinder port area for induction and exhaust. Such piston speeds are speeds within the limits of presently available materials, bearings, mechanical balancing etc., as are known in the four-cycle engine art. The specific fuel consumption of the engines of this invention approximately equal the specific fuel consumption of four-cycle engines of comparable cylinder size and may be about one-half as much as the specific fuel consumption of fuel mixture scavenged two-cycle crankcase loopscavenged internal combustion engines presently available, such engines being the commonly known outboard motor engines and similar designs.

Referring now to FIGURE 2, there is illustrated a slightly modified form of engine embodying the invention. In the engine shown in FIGURE 2 the cylinder 11 is made bent, that is to say the upper portion 111D of the cylinder 11 has its axis set at an angle of B to the axis of the lower portion of the. cylinder which is the cylinder 11. The angle B is preferably a small angle less than preferably in the neighborhood of 10 to 40".

'In FIGURE 2 all portions of the engine below the line 44 are precisely the same as those already described with reference to FIGURE 1. Those portions of the engine which are above the line 44 are similar to those shown in FIGURE 1, with the modifications mentioned above. In order to correlate the parts of the two engines in FIG- URES 1 and 2, the numerals designating the parts of the engine above the line 44 in FIGURE 2 are the same as those shown in FIGURE 1 except units higher. 7

Thus the upper portion of the cylinder is portion 111D (which corresponds to the upper portion 1 1D of FIGURE 1) and has a diameter which is less than that shown in FIGURE 1 and its axis is displaced at an angle of B. The amount of this angular displacement may be varied. It is less than 90 and is prefer-ably about 10 to about 40. illustrated is chosen to permit a compact combustion chamber with desirable location of a spark plug boss and aperture at 61-62. Also this provides a squish area which produces a desirable degree .of turbulence as the charge is compressed. The reduction of diameter of the portion 111D of the cylinder ascompared to portion '1'1C permits the use of a somewhat longer stroke 137R, as compared to crankstroke 37R of FIGURE 1, and also makes for a more compact combustion chamber. In the engine shown in FIGURE 2 the volumetric displacement attributable to the piston 142 moving in the cylinder 111D is the same as'in the engine shown in FIGURE 1, namely about 10% to about 50%, preferably about 20% to about 30% of the displacement attributable to the movement of piston 30 in the portion 11G of cylinder 11. Since the diameter of the cylinder 11 is decreased, above line 44 44, the crank throw of crank 137 may be increased somewhat. Ports 14.4 and their positions are proportioned according to the dictates of area and timing and fully open when the piston is in its uppermost position, as shown in full lines in FIGURE 2. Otherwise the upper portion of the engine shown in FIGURE 2 is the same as that shown in FIGURE 1, the crank case 132 being split at the flanges The amount of angular displacement specifically 134 so as to permit assembly of the crankshaft 135, having 'crankwheel 136 and crankpin 137 thereon. The piston 142 is connected by the connecting rod 138 to the crankpin 137. Again, the crankshaft 137 is provided with a toothed sprocket 148 which is connected by the toothed belt 149 to the toothed sprocket 47 on the lower crankshaft 25.

The pistons 30 and 142 may be relieved with reference to each other so that they do not engage when they are in the dotted line position. Thus departures may be made from the simple dome design, so as to improve combustion chamber layout. It will be appreciated that if the angle B is desired to be decreased, that this can be done by reducing the size of the spark plug boss 61.

The rotation of the upper crankshaft 135 is as shown by arrow 139 and the crank pin 137 leads by A the rotation of the crankpin 27. As the pistons 30 and 142 approach their dotted line positions, as shown in FIGURE 2, they compress between them the previously induced charge, and shortly prior to reaching a point of maximum compression the spark at spark plug 64 ignites the charge and the power stroke begins, the pistons being driven away from each other during the power stroke. The upper edge of the piston 142 reaches the lower or leading edge of the exhaust ports 144 in advance of the time that the upper edge of the piston 30 reaches the upper edge of the induction ports 14 and consequently the expanding charge, which is still under a considerable pressure within the cylinder, is permitted to escape through the ports 144, in the direction of arrows 151.

The downward motion of the piston 30, as previously described, compresses the previously induced charge in the crankcase 10, and as the piston 30 begins to uncover the upper edges of the ports 14, this charge compressed within the crank case will pass upwardly through the transfer passageway and through the ports 14 and into the cylinder 11. This charge flows upwardly via arrows 50, the desideratum, as previously mentioned, being that it shall advance frontally pushing upwardly before it the already burned and spent gases which are moved more or less as a plug upwardly, and consequently in an upward unifiow direction, with result that they are caused to flow out through the exhaust ports 144 via arrows 151. While the ideal condition of no mixing between the inflowing and outfiowing charges is most diflicult of attainment, yet it has been found that in the present engine a minimum of such mixing can be attained with the consequence that there is experienced a specific fuel consumption in this two-cycle uniflow crankcase-scavenged engine, which is comparable to the specific fuel consumption in the best quality of four-cycle engines of similar cylinder size, and the horepower output of the engine of the present invention will, on an equivalent basis, approach approximately twice as much as that of an overhead-valve fourcycle engine.

In FIGURES 1 and 2, in each of the engines illustrated the cylinder 11 has a lower cylinder portion 11C and one upper cylinder portion (11D or 111D) and one piston in the latter portion serves to perform the exhaust valve function for the whole two-portion cylinder 11. Thus in FIGURE 1 it is a simply the upper portion 11D of the cylinder 11, together with the piston 42, which serves to perform the exhaust valving function. In FIGURE 2 the upper portion 111D of the cylinder 11 is made of somewhat smaller diameter than the lower portion 11C of cylinder 11 and is set at an angle B with reference to the axis of the cylinder 11. According to the present invention the exhaust valve cylinder portion may be made as one or two or more cylinders. Thus in FIGURE 3 there are two upper portions of cylinder 11, these being the two cylinder portions 111R and 111L. These two cylinder portions 111R and 111L perform the exhaust'valving function for the whole cylinder of which the main portion is 110. In FIGURE 6, four such cylinders (upper cylinder) portions are provided, these being the cylinder portions 211A, 211B, 211C 8 and 211D, see FIGURE 7, and these in concert perform the exhaust valving function.

According to the present invention the total Volume of the cylinder portion (or portions) which perform the exhaust valving function may be one such cylinder portion as in FIGURES l and 2, or may be two such cylinder portions as shown in FIGURE 3 or more than two cylinder portions as shown in FIGURES 6 and 7. An advantage of using a greater number (than one) of such cylinder portions for performing the exhaust valving functions is that a greater wall area and hence greater exhaust port area is thus provided around the periphery of several cylinder portions, for a given displacement volume devoted to such upper cylinder portions. It is to be understood that regardless of the number of exhaust cylinder portions used for each main (or wor or induction) cylinder portion, the total of their volumes (whether one, two, four or more) is from about 10% to about 50% of the volume of the main clyinder portion, preferably about 20% to about 30% thereof. However, the greater the number of exhaust pistons per main piston, the smaller the relative exhaust piston displacement is generally required in order to achieve a given exhaust port area and timing. Also, with a greater number of exhaust pistons more freedom results in spark plug location and combustion chamber shaping, leading in turn to increased thermal efficiency.

In FIGURE 3 those parts of the complete engine which are below the line 4444 (which is also section line 55, in this illustration) are the same as in FIGURES 1 and 2 and therefore need not be described again. Comparing FIGURES 2 and 3, while FIGURE 2 had one exhaust valving cylinder portion 111D, the engine shown in FIGURE 3 has two exhaust valving cylinder portions 111R and 111L. The numbers applied to the various parts of these two cylinder portions correspond to those shown in FIGURE 2 except that they are designated R and L depending on whether they are the right (exhaust) cylinder portion or the left (exhaust) cylinder portion. Thus the right cylinder portion 111R is provided with a piston 142R operated by the piston pin 141R and connecting rod 138R, crankpin 137R on crankshaft R operating in the crankcase 132R. Precisely the same parts are shown for the cylinder portion 111, these being designated with the L sufiix and corresponding numerals. Both the crank shafts 135R and 135L are provided with drive pulleys 148R and 148L which are driven through a toothed belt 149RL from the driving pulley 47 on the crankshaft 25. Accordingly all three crankshafts (25, 135R and 135L) and their related parts, are moved in synchronism in the direction of arrows 139R and 139L. The crankpins 137R and 137L may lead by a few degrees (Angle A) the motions of the crankpin 27, as previously described with reference to FIGURES 1 and 2. When the piston 30 and pistons 142R and 142L are adjacent, they are in the position shown in dotted lines FIGURE 3. It may be noted that the pistons 142R and 142L may be provided with upper surfaces which are dished, so as together to provide a compression space 70 which is more or less dome-shaped, and approaches the theoretical ideal in design. Two apertures for spark plugs are provided at 64, and the plugs 64A and 64B (see FIGURE 4) may be provided in the dome. A desirable central location for the spark plug(s) is thus provided. For the purpose of mechanical simplicity, only a single spark plug may be utilized. One or more of the spark plugs may be replaced by fuel injection nozzles, as desired.

In operation the piston 30 and the pistons 142R and 142L in concert approach each other, moving from their full line positions to their dotted line positions as shown in FIGURE 3, thereby compressing the previously induced charge between them. Just prior to reaching the point of maximum compression the spark occurs or in the case of a diesel engine fuel is injected. Thus the ignited charge drives against the pistons, which then begin to move away from each other in sychronism according to the motions of the crankshafts 2.5 and 135R and 1351., and their related parts. The timing of the motions of the pistons 142R and 142L is such that they begin to uncover the lower edges (leading edges) of the exhaust ports 144R of cylinder 111R respectively of the exhaust ports 144L of cylinder 111L, slightly in advance of the time that the piston 30reaches the upper edges of the ports 14. Consequently the burned gases, which have of course expanded due to the motion of the pistons but which are still at a considerable pressure within the cylinder, are permitted to pass out through the ports 144R and 144L, and through the exhaust manifolds, not shown. Shortly thereafter, as the piston 30 begins to uncover the upper or leading edges of the ports 14 and the charge (which as described with reference to FIGURES 1 and 2 has been compressed in crankcase is permitted to pass through the transfer passageway and through the ports 14, moves as shown by the arrows 50 into cylinder 11, where in a unifiow form of motion such gases-move with minimum intermixing with the exhaust gases above them and push such gases upwardly into the two exhaust cylinder portions 111R and 111L and via arrows 151R and 151L out through the exhaust ports 144R and 144L.

The greater number of exhaust cylinder portions 111R and 1111, (two instead of one) for controlling the exhausting of the gases, provides a greater total dimension of cylinder wall periphery per unit volume (equalling the peripheries of the cylinder portions 111R and 111L added together) wherein the designer may place exhaustports 144Rand 1441.. A more favorable combustion chamber shape and spark plug location, as compared with use of a single exhaust piston as in FIGURES 1 and 2, also results.

Where complexity is not objectionable, an even greater number of exhaust (supplemental) cylinder portions may be utilized, this being illustrated in FIGURES 6 and 7 where a total of four such cylinder portions 211A, 211B, 211C and 211D are provided. Whereas FIGURE 3 shows a simple V ofupper exhaust cylinder portions, these being 111R and 111L in the engines shown in FIG- URES 6 and 7, there are in FIGURE 6, two blanks having two exhaustcylinder portions, making a total of four cylinder portions for providing the exhaust func tion. Even more might be provided if the matter of complexity is not objectionable. In the engine shown in FIGURES 6 and 7, the one bank of such exhaust cylinder portions are the cylinder portions 211A and 211B (see FIGURE 7 and FIGURE 6) and the other bank of cylinder portions are 211C and 211D. These are made precisely similar to those shown in FIGURE 3 and need not be further described. Each cylinder portion has a piston, each piston is made as shown in FIGURE 3 so as to uncover cooperating exhaust ports. The pistons in cylinder portion 211A and 211B are operated by a single crankshaft 235L which operates in the crankcase232AB. On this crankshaft is a pulley 248L which is driven by the belt 249RL. A similar crankcase and crankshaft and pulley (not shown, as these would be behind 232AB, 235L and 248L) are provided for operating in unison the pistons in the cylinder portions 211C and 211D.

Taken together the volumetric displacement accountable by the pistons moving in supplemental (exhaust) portions 211A through 211D shall be about 10% to about 50% preferably about to about of the volume accountable by the movement of piston 30 within the main cylinder portion 110. The arrangement shown in FIGURES 6 and 7 has the additional advantage of providing a dome-shaped compression chamber together with a central location of a single spark plug or fuel injection nozzle at 64X. Otherwise the engine is the same as illustrated and previously described with reference to the other figures.

Throughout this specification and in the claims the term cylinder is intended to include the entire communicating space served by all pistons in it, including the configuration of FIGURE 1 wherein the cylinder is of one uniform diameter and is served by two pistons; the configuration of FIGURE 2 where cylinder portions of different diameters are used and the configurations of FIGURES 3-7 where a main cylinder portion is in direct communication with but is branched into two or more supplemental (exhaust) cylinder portions.

The engines shown in FIGURES 1, 2, 3 and 6, in each instance illustrate a one cylinder engine. It will be understood that all of these illustrated engines can be made multiple cylinder engines by merely adding more cylinders in parallel or in angular configuration, as is well known, with appropriate lengthening of the crankcases and crankshafts. Usually only one drive arrangement will suffice for driving the crankshafts in unison, regardless of the number of cylinders served by the crankshafts.

It'will also be noticed that in each of the engines described and illustrated, the displacement volume of the crankcase pumping means-is solely associated with the crank shaft of the induction piston. The exhaust pistons and crankshafts have no function as crankcase scavenging pumps; By this means any difficult and troublesome transfer piping from the exhaust. piston crankcases to the cylinder induction ports is eliminated and at the same time the full throttle delivery ,or scavenging ratio can be kept to'a desirable percentage in the interest of low spe cific fuel consumption. It should also be pointed out that the motion of the exhaust pistons is in general diametrically opposed to that of theinduction piston, permitting an engine of nearly perfect reciprocating force balance.

As many widely apparently different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein.

What I claim is:

1. An improved two-cycle crankcase-scavenged internal combustion engine compirsing:

a cylinder having a main cylinder portion and a supplemental cylinder portion directly connected to each other,

a main piston in said main cylinder portion, and a supplemental piston in said supplemental cylinder portion,

a main crankcase for said main cylinder portion having a main crankshaft therein,

a main connecting rod connecting the main crankshaft and main piston for oscillating the piston as its crankshaft rotates,

an induction passage into the main crankcase having value means therein for preventing outflow of gases from the main crankcase when gases are compressed therein,

induction ports in the wall of the main cylinder portion positioned to be uncovered by the main piston as it is moved towards the main crankcase by the main connecting rod and main crankshaft, transfer passages connecting said induction ports to the interior of the main crankcase;

said main crankcase and main piston forming the sole pumping means for scavenging said cylinder,

a supplemental crankcase for said supplemental cylinder portion, having a supplemental crankshaft therein,

a supplemental connecting rod connecting the crankshaft and supplemental piston for oscillating said supplemental piston as its crankshaft rotates,

exhaust ports in the wall of the supplemental cylinder portion positioned to be uncovered by said supplemental piston as it moves towards said supplemental crankcase,

mechanical means connecting the main and supplemental crankshafts for driving them in unison and for thereby reciprocating the main and supplemental pistons towards each other and then away from each other,

the dimensions of the portions of said cylinder and the amount of movement of the pistons therein being such that the volume displaced by the movement of the supplemental piston is from about to about 50% of the volume displaced by movement of the main piston, an opening for ignition means fuel injecting means or the like in the cylinder and leading into that portion of said cylinder which is between the pistons when they are closest together.

'2. The engine of claim 1 further characterized in that the volume displaced by the movement. of the supplemental piston is in the range of about 20% to about 30% of the volume displaced by the movement of the main piston.

3. The engine of claim 1 further characterized in that the axis of the cylinder portions are at an angle to each other.

4. The engine of claim 1 further characterized in that the supplemental cylinder portion is of the same diameter as the main cylinder portion.

5. The engine of claim 1 further characterized in that the supplemental cylinder portion is of a lesser diameter than the main cylinder portion.

6. The engine of claim 1 further characterized in that the supplemental cylinder portion is of a lesser diameter than the main cylinder portion and further characterized in that the axis of the cylinder portions are at an angle to each other. 7

7. The engine of claim 1 further characterized in that there are two supplemental cylinder portions in communication with the main cylinder portion, each having its supplemental crankcase, crankshaft connecting rod and piston, each of said supplemental crankshafts being connected to said main crankshaft by said mechanical means so as to turn in unison therewith.

8. The engine of claim 1 further characterized in that there are two supplemental cylinder portions in communication with the main cylinder portion, each having its supplemental crankcase, crankshaft connecting rod and piston, each of said supplemental crankshafts being connected to said main crankshaft by said mechanical means so as to turn in unison therewith and said supple mental cylinder portions having axes that are at an angle to the axis of the main cylinder portion.

9. The engine of claim 1 further characterized in that there are two pairs of supplemental cylinder portions in communication with said main cylinder portion.

10. The engine of claim 9 further characterized in that the axes of the supplemental cylinder portions of each pair are in a common location plane and the location planes of the axes for both pairs are at an angle to the axis of the main cylinder portion.

11. The engine of claim 1 further characterized in that there are two pairs of supplemental cylinder portions in communication with said main cylinder portion, each pair of said supplemental cylinder portions having a common crankshaft, said two crankshafts one for each pair of supplemental cylinder portions being driven in unison from said main crankshaft by said mechanical means.

References Cited by the Examiner UNITED STATES PATENTS 871,539 11/07 Van Auken 123-51 1,273,229 7/ 18 Hurlbrink 123-51 1,699,111 1/29 Lyons 123-51 2,054,232 9/36 Schneider 123-51 2,367,565 1/45 Curtis 123-65 2,639,699 5/53 Kiekhaefer 123-73 2,669,979 2/54 Kiekhaefer 123-73 2,768,616 10/56 Venediger 123-51 2,831,359 4/58 Carle 123-90.10 2,886,018 5 5 9 Cuddon-Fletcher 123-51 2,894,405 7/59 Carle 123-495 2,949,899 8/60 Jacklin 123-51 FOREIGN PATENTS 20,063 9/09 Great Britain. 225,249 1 l 24 Great Britain.

FRED E. ENGELTHALER, Primary Examiner.

Claims (1)

1. AN IMPROVED TWO-CYCLE CRANKCASE-SCAVENGED INTERNAL COMBUSTION ENGINE COMPRISING: A CYLINDER HAVING A MAIN CYLINDER PORTION AND A SUPPLEMENTAL CYLINDER PORTION DIRECTLY CONNECTED TO EACH OTHER, A MAIN PISTON IN SAID MAIN CYLINDER PORTION, AND A SUPPLEMENTAL PISTON IN SAID SUPPLEMENTAL CYLINDER PORTION, A MAIN CRANKCASE FOR SAID MAIN CYLINDER PORTION HAVING A MAIN CRANKSHAFT THEREIN, A MAIN CONNECTING ROD CONNECTING THE MAIN CRANKSHAFT AND MAIN PISTON FOR OSCILLATING THE PISTON AS ITS CRANKSHAFT ROTATES, AN INDUCTION PASSAGE INTO THE MAIN CRANKCASE HAVING VALUE MEANS THEREIN FOR PREVENTING OUTFLOW OF GASES FROM THE MAIN CRANKCASE WHEN GASES ARE COMPRESSED THEREIN, INDUCTION PORTS IN THE WALL OF THE MAIN CYLINDER PORTION POSITIONED TO BE UNCOVERED BY THE MAIN PISTON AS IT IS MOVED TOWARDS THE MAIN CRANKCASE BY THE MAIN CONNECTING ROD AND MAIN CRANKSHAFT, TRANSFER PASSAGES CONNECTING SAID INDUCTION PORTS TO THE INTERIOR OF THE MAIN CRANKCASE; SAID MAIN CRANKCASE AND MAIN PISTON FORMING THE SOLE PUMPING MEANS FOR SCAVENGING SAID CYLINDER, A SUPPLEMENTAL CRANKCASE FOR SAID SUPPLEMENTAL CYLINDER PORTION, HAVING A SUPPLEMENTAL CRANKSHAFT THEREIN,

Images