US2149793A - Internal combustion engine - Google Patents

Description

March 7, 1939. A. SCHEIBE INTERNAL COMBUSTION ENGINE Filed Sept. 29, 1936 2 Sheets-Sheet l In venivr: ALF/m) 50/5/35 13/ March 7, 1939. A. SCHEIBE INTERNAL COMBUSTION ENGINE Filed Sept. 29, 1936 2 Sheets-Sheet 2 Fig 4.

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C P.B-. w 5W n H w m By M F m M Patented Mar. 7, 1939 PATENT OFFICE INTERNAL COIWBUSTION ENGINE Alfred Scheibe, Dessau-Ziebigk, Germany, assignor to Junkers Flugzeug-und-Motorenwerk A. G., Dessau, Germany Application September 29, 1936, Serial No. 103,135

In Germany October 14, 1935 10 Claims. '(cl. 23-65 My invention relates to internal combustion v engines, more especially of the single-piston twocycle type. The invention is particularly conce ned with the means whereby the fresh gases 5 Y are fed to and the gases of combustion exhausted from the cylinder of the engine.

It is an object of my invention to provide an arrangement of the intake and exhaust ports which results in a higher efilciency of the engine than similar arrangements hitherto suggested.

In single-piston two-cycle engines as a rule two groups of ports are arranged in the wall of the engine cylinder, which are controlled by the piston. One of these groups of ports serves for 5 introducing the fresh gases under a certain pressure above atmospheric, whilethe ,other serves for exhausting the gases of combustion. -As a rule the exhaust ports extend somewhat farther, in the direction of stroke, towards the combustion chamber than the intake ports, so that when"the piston executes its outward stroke, it will first uncover the exhaust ports. In consequence thereof, until the intake ports are uncovered, a great partof the total quantity of exhaust gases can escape from the combustion chamber and the pressure of the exhaust gases still left in the cylinder therefore decreases quickly, so that on the intake ports being uncovered, there is no danger that exhaustgases might enter the fresh gas supply. On its inward stroke the piston first closes the intake ports and only thereafter the exhaust ports. In the period of time between the closing of the intake and the exhaust ports the combustion chamber still communicates with the exhaust pipe through the still open exhaust ports. This involves the drawback that on the exhaust ports being closed and compression started, the fresh gasesin the working cylinder cannot be acted upon by a pressure higher than the pressure prevailing in the exhaust pipe, so that it is not possible to simply charge up the cylinder. My invention is based on the conception that a faultless operation of two-cycle engines with 45 a recharging of the working cylinder is possible also in the case where merely intake and exhaust .ports controlled by the working piston are provided and the intake ports extend farther towards the dead space than-the exhaust ports. In order to render this possible, it is necessary that after the exhaust ports have started to open, the exhaust gases expand very quickly and that the fresh gases enter the working space' with high velocity. To attain this end, I form the exhaust 55 conduits with a far greater total cross-sectional ton during its return stroke.

area of passage and preferably with several times a cross-sectional area, for instance the twoto fourfold, than the intake ports. These intake ports are of uniform shape and size and are so designed as to form simple and plain paths of 5 flow in both directions, containing no members,

such as nozzle inserts, valves etc., which might Fig. 4 is a diagram illustrating the size of the entrance and exhaust" surfaces uncovered by the piston on its working and return stroke, while .Fig. 5 is the corresponding crank gear diaram. i

Referring to the drawings and first'to Figs. 1, 25 2'and 3, l is the inner wall of the engine cylinder and 3 and 4 are the intake an exhaust conduits, respectively, ending in the inner wall of the cylinder near the outer end uncovered by the pisof these conduits form theintake and exhaust ports 5 and 6, respectively, all of which are controlled by the piston 2, exclusively. The intake conduits 3 have'the form of simple plain borings, the axes of which cross the cylinder axis in 35 oblique direction, being-spaced from it by a distance m which is smaller than the radiusr of the cylinder cavity, so thatthe fresh gas enters the cylinder space in about a tangential direction and with a velocity component directed to- 40 wards the deadspace. are simple perforations provided in the cylinder wall, which lead to a receiver 8' encircling the cylinder. The borings formingthe intake conduits 3 extend across the parts or bridges 9 of the cylinder wall between the exhaust conduits 4 and their openings II), which communicate with the fresh gas receiver I I, are spaced farther-from the combustion chamber l2. than the outer openings 1 of the exhaust conduits 4 in the exhaust gasreceiver 8, while their openings (inlet openings' 5) in the inner wall I of the cylinder extend farther towards the combustion chamber l2 than the openings 6 of the exhaust conduits 4. Thus the inlet openings 5 are uncovered by The inner ends The exhaust conduits lr conduits offers particular advantages.

the'working piston 2 on its outward stroke earlier and on its inward ,stroke are closed later than the exhaust openings E.

This arrangement of the intake and exhaust I The arrangement of the intake conduits in the bridges left ,between the exhaust conduits allows the fresh gases entering through the intake conduits to exert a cooling efiect of the bridges, the outer walls of which are acted upon by the hot exhaustports are partly situated between the exhaust ports 6, the space available in the inner cylinder wall for the accommodation of the ports is particularly \wellutilized, more especially in connechaust ports which corresponds substantially to a triangle with strongly rounded comers. Here the magnitude of the cross-sectional areas of passage of the exhaust conduits 4 is several times that of the cross-sectional area of passage of the intake conduits 3. The peculiar design and arrangement of the intake conduits further allows the fresh gases traversing these conduits with high velocity to ent the cylinder in a uniform circumfe ential dist bution and substantially in tangential direction, however with a velocity componentdirected axially to the combustion chamber, so that thesefreshf gasesafter leaving the conduits, move towards the combustion chamber under the form of a multiple thread screw line,

extending in close proximity to the inner cylinder wall. In consequence thereof the outer zone of the cylinder chamber is first filled with fresh gases and the remainderof the exhaustfgases is forced towards the exhaust ports through the central part of the c i'inder space. When the piston has reached its o'uer dead center position, the ratio of the uncovered surfaces of the exhaust and intake ports is greatest and the pressure in the cylinder has then reached its minimum. During the inward stroke of the piston the pressure then rises rather quickly since the exhaust ports are gradually covered, while the fresh gas supply at first continues as before and continues also after the exhaust ports have been closed, until-ultimately the piston has also closed the intake ports. The interior of the cylinder is now' filled with a body of fresh gases which owing to its inertia continues circulating therein and is placed under increased initial pressure. This high circulation velocity of the cylinder charge is particularly advantageousin internal combusing a direct extension of the working cham-' ber hasthe form of a plain-revolution space devoid of any secondary spaces, while the fuelisinjected, for instance by means of an injection nozzle 20, directly into the dead space, since under these circumstances the air of combustion is carried into particularly intimate contact with the injected fuel.

In the embodiment of my invention illustrated in the drawings a conduit l3 of annular cross-section is provided between the main fresh gas receiver H and the outer openings Moi the intake tion with the contour shown in Fig. 1 of the extion engines, in which. the dead space formconduits 3. This conduit l8 has a comparatively small cross-section and a length such that the total passage of gas flow from the fresh gas receiver I I up to the intake conduit openings 5 in the inner wall of the cylinder is considerably longer than the length of the exhaust conduits 4 which should be as-short as possible. I thus obtain that the exhaust gases which, on the intake openings being uncovered, enter the intake conduits 3, can only enter the narrow connecting conduit l3, however not the main fresh gas receiver ll, so that they can substantially only displace the fresh gases in these narrow conduits 3 and I3 without being able to mix with them in the large main receiver ll.

In the diagram ofjFig. 4 the surfaces uncovered during the working and return stroke of the piston 2, of the intake and exhaust openings are plotted in dependency from the crank angle.

' In the point E and at an angular distance on from the outer dead center point Ta begins the uncovering of the intake ports 5 during the working stroke of the piston. The uncovered surface of these portsrwhich is represented by the ordinates ft of the line e, gradually increases until in the point E1 at an angular distance as from the outer dead center point Ta the intake ports are uncovered altogether. They remain altogether open while the piston continues on its outward stroke up to the dead center point Ta and subsequently returns until it reaches the point Ei at an angular distance a'z from the dead center point Ta. From the point'E'i on the free surface of the intake ports is again gradually reduced by the inwardly travelling piston until it has reached the point E' at an angulandistance '1 from the outer dead center point Ta, at which the intake ports 5 are altogether covered by the piston.

The uncovering of the exhaust ports 6 starts in the point A at an angular distance 51 before the dead center point Ta, which distance is smaller than the angular distance 111, but greater than the angular distance 012. This uncovering continues up to the dead center point Ta and after this point has been overstepped, the exhaust ports are again gradually covered by the piston, until, in the point A at an angulardistance 5'1 from the dead center point Ta they are covered altogether.

The surfaces of the exhaust ports (represented by the ordinates is of the line a) which are un-;

covered at any particular moment, are considerably larger over-the greatest part of the exhaust angle pi+fl1 than the uncovered surfaces i of the intake ports. There thus results a very quick increase of the cross-sectional areas of exhaust is from the uncovering point A on, so that now the exhaust gases can escape very quickly from the cylinder, while shortly thereafter .(in the point E1) the intake portsare already uncovered altogether, so that also the scavenging and charging can now take place freely.

Tests made with an engine of this kind have shown-that the arrangement of the intake and exhaust ports above described results in particularly favorable conditions of operation. This is in contrast to the apparently obvious danger that, if the intake ports are already uncovered before the exhaust gases have started escaping, a considerable quantity of these latter gases, being still acted upon by a considerable pressure,

: would enter the fresh gas receiver and that in consequence thereof the engine would develop only a. relatively low output. That this does not hagpan, can be explained as follows: When be- Ill ber increases; on the other hand the piston at first only uncovers small parts of the surfaces of the intake ports. Thus the bulk of the exhaust gases at first remains in the working chamber and only a small part passes into the fresh gas supply through the still partly closed intake ports.

On continuing its stroke the piston then also uncovers the exhaust conduits and since the crosssectional area of passage of these ports is considerably greater than that of the intake conduits, the exhaust gases in the cylinder will now expand quickly and consequently scavenging and recharging with the fresh gases can now follow. The comparatively small cross-sectional areaof the intake. conduits results in a high velocity of the inflowing freshgases, which in this case is favorable, since a fast flowing current of scavenging gas will not be dispersed as easily as a slowly flowing one, but will penetrate the working chamber up to the inner end and will thus scavenge the exhaust gases very completely. The holding together of the scavenging gas current is favored also by the fact that the intake conduits open in the cylinder wall in about tangential direction so that the scavenging gas current will flow in a contact with the cylinder wall.

.are required to move in synchronism with the piston. Therefore the two-cycle engine provided merely with piston-controlled intake and exhaust ports is the ideal high speed motor as far as construction from the designers point of view is concerned. Hitherto, however, nobody had succeeded to increase the output per unit .of strokevolume in the two-cycle engine toa similar extent as has long been attained in high speed four-cycle engines by pre-compressing the charge.

The present invention therefore provides a solution of the important problem of providing an engine which in view of the particularly great simplicity'of design is excellently suited for high speed operation and which at the same time allows recharging, which results in a particularly high output per unit of stroke-volume.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

I claim: 1. In an internal combustion engine of the single-piston two-cycle type the combination of a cylinder and a piston reciprocable in said cylinder, the wall of'said cylinder being formed near its outer end, uncovered by the piston on its outward stroke, with intake and exhaust ports, each kind of ports being arranged in a circle, all said intake ports being substantially alike and having the'form of simple plain passages in both. directions of gas flow, their openings in the inner wall surface of said cylinder extending farther in the direction towards the dead space than those of the exhaust ports, the exhaust ports having a total cross-sectional area of passage considerably exceeding that of the intake ports, said piston being the sole means controlling the passage of'air and gas through said ports.

2. The engine of claim 1, in which the circles of intake and exhaust ports are so arranged that the inner openings of the intake ports extend into the spaces between the inner openings of the exhaust ports.

3. The engine of claim 1, in which an intake port is arranged between each pair of adjoining exhaust ports. v

4. The engine of claim-1, in which the intake ports extend through the bridges left between the pairs of adjoining exhaust ports.

5'. Thaengineof claim 1, in which the inner openings of the intake ports end short of the part of the cylinder wall uncovered by the piston at the end of its outward stroke. while extending into the part of the cylinder wall situated between the pairs of adjoining exhaust ports.

6. The engine of claim 1, in which the straight intake ports extend substantially tangentially to the cylindrical space in the cylinder and obliquely to the cylinder axis with their openings in the inner cylinder wall in closer proximity to the combustion chamber than their openings in the outer cylinder wall.

7. The engine of claim 1, in which-the intake and the exhaust ports cross each other within the cylinder wall with the openings of the exhaust ports in the outerwall surface located in closer axial proximity to the combustion chamber than the openings of the intake ports in said outer wall surface.

8. The engine of claim 1, comprising an exhaust gas receiver and a fresh gas receiver, both encircling the cylinder, the exhaust gas receiver being located in closer axial proximity to the combustion chamber than the fresh gas receiver.

9. The engine of claim 1, comprising an exhaust gas receiver and a fresh gas receiver, both encircling the cylinder, the exhaust gas receiver being spaced from the inner exhaust port openings as little as possible, while the inner intake port openings are spaced considerably farther from the fresh gas receiver.

'l'iirThe engine of claim 1, in which a connecting conduit of annular cross-section having a relatively small cross-sectional area of passage is inserted between the fresh gas receiver and

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