US2249354A - Internal combustion engine - Google Patents

Description

ombuJfiIb/e July 15, 1941, H. A. GEHRES INTERNAL COMBUSTION ENGINE Filed June 24, 1939 INVENTOR HEW/ TrA CEHRES. BY v W, 4 H4 ATTORNEYS Pum Patented July 15, 1941 INTERNAL COMBUSTION ENGINE Hewitt A. Gehres, Mount'Vernon, Ohio, assignor to Cooper-Bessemer Corporation, Mount Vernon, Ohio, a corporation of Ohio Application June 24, 1939, Serial No. 280,938

7 Claims. (Cl. 123-65) This invention relates to improvements in internal combustion engines, and particularly to engines of the two-cycle type disclosed in my copending application Serial Number 146,185, filed June 3, 1937, of which this application is a continuation in part.

Two-cycle engines in general have a number of disadvantages which may be overcome by the invention of my copending application and by the further improvements of the present inventioni With the usual two-cycle engine, a mixture of air and gas is drawn into a chamber through a check valve by the action of the power piston during its compression stroke. This charge is compressed during the expansion stroke of the piston and near the end of the expansion stroke and when the intake and exhaust ports are opened, the mixture of air and gas flows into and to some extent through the cylinder, forcing out the burned gases and leaving a mixture in the cylinder of widely varying and often unsatisfactory combustion characteristics. Regulation of such prior engines has been afiected by way of varying the quantity of gas admitted with the air, and since the quantity of air admitted remains practically constant, the percentage of gas in the mixture varies widely. Since for ideal or even satisfactory combustion conditions, this percentage has to be kept within a very narrow range, it is evident that at light loads and at extremely heavy loads, the mixture becomes either too lean or too rich to ,give proper combustion. As a result, in prior two-cycle engines, the firing is intermittent and the operation of the engine is irregular and uneconomical. The low economy of this type of engine is not only caused by irregular operation but also because of the scavenging being done with a mixture of air and gas, a substantial part of the gas escapes through the exhaust ports unburned.

According to the invention of my said copending application and also with the simplified and improved arrangements of this application, an engine construction and method of operating the same is provided whereby scavenging" air may two different zones within the combustion chamber, one of the zones being for example supplied with a fuel and air mixture having substantially the ideal percentage of fuel for prompt and substantially complete combustion, and the otherzone being supplied with a quantlty'of gasor other fuel in which the percentage of fuel may be widely varied to'meet different loads but is generally too rich for ideal combustion conditions. With this type of arrangement and method,.the atmosphere within thecombustion chamberis more or less Stratified, i. e. with first a stratum remote from the scavenging ports and comprising substantially an ideal combustible mixture, second, a stratum embodying a variable quantity of fuel generally too rich for ideal combustion and, third, a stratum or volume of air remaining from the scavenging operation. Upon compression of these strata by action of the piston, ignition and combustion of the first causes the second stratum to be forced into admixture with the air stratum and at some moment when the second stratum is being mixed with the air, conditions will be ideal for thorough combustion of the fuel of the second stratum. With this operation, regular firing, even with widely varying loads, is insured with no substantial loss of unburned fuel. The two supplies of fuel may be introduced and compressed by apparatus forming part of andautomatically actuated by action of the engine proper, for example, by providing an air or air and gas compression chamber at the external surface of the piston and pressure-operated valves under control of the compression chamber. Or, if desired, one or both of the fuel supplies may be introduced under pressure through mechanically operated valves suitably timed to deliver their respective charges into the cylinder shortly prior to or after closure of the exhaust ports, so as to minimize or prevent loss of unburned fuel. Also, if desired, both'of the separate fuel supplies may be varied either manually. Or automatically by well-known governing apparatus.

- The invention of this application is more particularly directed to the simplification of and improvement upon the construction and operation.

check valve 22 into a chamber 23.

connection with the accompanying drawing which forms a part of this specification and illustrates merely by way of example a preferred form of the invention. The invention consists in such novel features, arrangements and. combination of parts as may be shown and described in connection with the construction herein disclosed.

In the drawing, Fig. 1 is a longitudinal sectional view of an engine cylinder and adjacent parts illustrating one example of the invention;

Fig. la is a detail illustrating cam-actuation of the valves of the Fig. 1 showing; and

Fig. 2 somewhat schematically indicates the stratified conditions in the engine cylinder at the beginning of compression of the fuel charges.

The engine as shown in Fig. 1 comprises a cylinder I and a removable cylinder head I I formed with an elongated cavity or chamber l2 comprising an extension of the combustion chamber including the cylinder. A piston is shown at I3 connected to a piston rod I 4 which in turn may be connected to a cross-head l5 and connecting rod IS, the latter being connected to a suitable crank shaft (not shown). The cylinder may be substantially surrounded by a suitable water jacket or similar cooling means. For example, as

here shown, cooling fluid cavities are provided as at l1 and I8 surrounding respectively the cavity I2 and the cylinder.

Either air or a mixture of air and combustible gas may 'be admitted to a chamber IS, the air through a pipe and the gas or fuel through a jet 2| whereby the fuel is aspirated in with the air. When the piston is moving on its compression stroke, the air or air and gas will be drawn fromchamber l9 through-a suitable form of flap The check valve comprises a closure disk 22a, normally covering a valve opening 22b and resiliently held against a shoulder 220 of the valve housin 22d, by means of a spring 22c. It will be noted that the chamber 23 is open through passages 33 and 24 to the under surface of the piston l3, 1. e. the piston surface external to the combustion chamber. The chamber 23 may be closed with respect to the crank case by any suitable means such as a flanged member 25 having a central aperture with suitable packing, permitting the piston rod to reciprocate therethrough; The member 25 may be mounted on an extension 26 of the crank case, which extension carries the ways 21 for the cross-head.

During'the expansion stroke of the piston, the air or air and gas in chamber 23 will be compressed, and also for a time, the resulting pressure will cause some of the air or air and gas to be forced through a port 28 formed in the wall of the cylinder at its lower end, and thence into a passage 29. But approximately at the termination of the expansion stroke, it will be noted that the lower edge 30 of the piston,'will act to close the port 28 and keep this port closed until after the compression stroke is under way, thereby trapping the air or air and gas under pressure in passage 29.

The cylinder may be provided with exhaust ports, as at 3|, in a position such that the same will be opened when the piston approaches the end of its expansion stroke, and soon thereafter an air intake port 32 connected-to chamber 23 through a passage 33, will be opened for admitting air or a mixture of air and gas under pressure from chamber 23 into the cylinder H) for scavenging purposes. The upper face of the pisbly deflect this air or air and gas upwardly into the cylinder in order to cause thorough scavenging, and whereby some of this air, together with the burned gases, is forced out through the exhaust ports 3| to a suitable discharge connection.

Means are also provided as hereinafter described, for supplying, at the time of or shortly after this scavenging operation, a quantity .of a substantially ideal combustible mixture of fuel and air within the upper end or zone in the elongated cavity l2, and optionally also a variable quantity of raw gas or other fuel generally too rich for perfect combustion into a somewhat lower zone, for example, at a point near where cavity l2 joins the main body of the cylinder. The two supplies of fuel thus separately admitted to these zones will be more or' less stratified in the manner indicated in Fig. 2, and the scavenging air and burned gases during the scavenging operation will have little opportunity to mix therewith, and thus exhaust of unburned fuel from these sources, through the ports 3 I, will be avoided.

Referring now to the fuel intake means, a valve 35 may be provided at the upper end of chamber l2 for admitting the volume of combustible medium having the ideal mixture. This valve may comprise any suitable well-known type of poppet valve held normally closed by a compression spring 35 as shown. The combustible mixture which is being admitted through valve 35 may comprise gas or other fuel introduced through a suitable jet 31 and aspirated in with the fair in a chamber 38 admitted through conduit 39. The mixture may be controlled by any suitable wellknown adjustable valve means for the jet 31 and for the air inlet conduit 39, respectively. The chamber 38 may be connected through a suitable flap check valve 40 to a chamber 4|, which latter chamber in turn communicates with the valve 35 and also with passage 29, as shown.

The combustible mixture which is generally over-rich in fuel may be introduced through a valve 42 located, for example, at the upper end of the main body of the combustion chamber and held normally closed by a compression spring 43 as shown. This valve 42 may be of a poppet type similar to valve 35 and may communicate, as through a passage 44, with a suitable source of fuel supplied under pressure, as from a pump 50. The operation of valves 35 and 42 may be made automatic by appropriate adjustment of the tensions in springs 36 and 43, so that they will, open and close at the proper intervals due to variations of pressure within the combustion chamber of the cylinder. Alternatively, and as shown by Fig. 1a, these valves may be mechanically operated,

v if desired, by suitable cams, such as 5|, operating ton-may be shaped as shown at 34, so as to suitaagainst the exposed ends 45 and 46 of the valve stems in the wellknown manner.

A spark plug or other suitable ignition means may be provided as at 41 at the upper end of the cavity l2, and energized with proper timing in any suitable well-known way.

The operation of the engine as shown may be summarized as follows: During the compression stroke of the piston, either air or a mixture of gas and air is drawn through valve 22 into the chamber 23. Since port 23 is now uncovered, a charge of .air and gas is also drawn in through valve 40. The valve for jet 31 is so adjusted as to control the fuel here admitted in relation to the air from inlet 39 as to give substantially an ideal combustion mixture. Some of this mixture as drawn into chamber 4| will also be drawn down into the upper end of passage 29. As the piston returns on its expansion stroke, the air or air and gas in chamber 23, willbe compressed and some will pass through port 28 and thereby cause compression of the charge within the upper end of passage 23 and chamber 4|. Then when the piston on its downward movement covers port 28, the mixture in 29 and 4| will be trapped under compression. Also at the end of the expansion stroke, the exhaust and air intake ports ideal combustible mixture into the chamber l2..-

that from the standpoint of economy, it is preferable to introduce only air through this valve and to supply fuel to valve 42 from a separate source rather than through valve 22. Alternatively, valve 42 may be entirely eliminated, in which event the introduction into chamber 23 of a mixture of gas and air from jet 2! and conduit lower stratum of the cylinder.

ment would, of course, reduce the economy of would be required, the mixture to be introduced thence into the engine cylinder through port 32 to provide an appropriate fuel mixture in the This arrangeoperation, inasmuch as considerable unburned fuel would be lost in scavenging at heavy loads.

Fuel economy is, however, of lesser importance compared to fundamental purpose of the invention, which is to provide an engine of the character described whichwill fire regularly under all Meanwhile, also upon suflicient reduction of the pressure in the cylinder, valve 42, if likewise made automatic in operation as explained, will momentarily open for admitting avolume of the'r'ich' fuel mixture into the upper region of the main body of the cylinder. Thereupon', the three strata, comprising the readily combustible mixture, the rich mixture, and air, respectively, will be established in general as indicated in Fig. 2.

Upon the succeeding compression stroke of the piston, the charge of the ideal mixture substantially remains within the cylinder extension l2 due to its elongatedshape, and this charge is compressed within the upper portion ofchamber n adjacent the spark plug 41, whereby prompt ignition of thischarge may be insured when the piston is near the end of its compression stroke. The ignition of the charge within the chamber 12 will thereupon cause the charge admitted through valve 42 to-be expanded downwardly and become mixed with the air or air and gas within the lower zone of the cylinder, wherebyat some moment, a good combustible mixture? will be formed in the main bodyof the cylinder and thereupon ignited, with assurance that thorough combustion of substantially all of the'fuel admitted to the cylinder will take place.

a The mixture admitted through valv 40 will ordinarily comprise only a minor part ofthe total cylinder charge. The major portion vofI the fuel may be introduced through valve 42. v

The engine may be provided with-'al suitable well-known type of governing means acting in a well-known manner to throttle eitherthe amount of fuel entering at valve 22 or at valve i2. Although the mixture coming in through valve 40 may generally and preferably be of 'a constant volume, however, if desired, governing means can also be applied to throttle the amount. of the mixture entering through this valve. If valves 35 and" are made automatic in op eration as explained, the valves will open and supply fuel to the combustion chamber at the same time that scavenging occurs, so that some of this fuel mayescape unused throughthe exhaust port. This tendency may be overcome by mechanically operating thes'e valves, for examintroduced through valve 22, some of this fuel will be lost during the scavenging operation, so

operating conditions including light loads at which prior engines or, this type are defective. This feature is attained with the present invention irrespective of the above-mentioned alternatives for supplying fuel and operating the valves.

In the appended'claimswhere reference is made to the admission of air to the chamber 23, it will be understood that such air if desired may be considered as accompanied by combustible gas.

While the invention has been described with respect to a certain, particular preferred example which gives satisfactory results, it will be under stood by those skilled in the art after understanding the inverition, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended thereforein the appended claims to cover all such changes and modifications.

I claim: 1

1. In a two-stroke cycle internal combustion engine, a cylinder, a reciprocating piston therein,

intake valves at the head end of the cylinder for admitting two different fuel mixtures at spaced points, intake and exhaust ports for scavenging air adjacent the face of the piston when at the end of its expansion stroke, a compression space at the external surface of the piston, a passage from said space to one of said intake valves, and a port in the cylinder wall and under the control of the piston for interconnecting said space and passage.

2. In a two-stroke cycle internal combustion engine, a cylinder, a reciprocating piston therein, means .for admitting and exhausting scavenging air adjacent one end of said cylinder, means adjacent the other end of the cylinder for admitting'two different combustion fluid mediums at separate points, in substantially a predetermined timed relationship with the admission and exhaustion of the scavenging air, means including theexternal surface of said piston for providing a supply of air or air and combustible gas under pressure, a passage for conducting the latter suppiston also in timed relationship with the admission and exhaustion of the scavenging air.

3. In a two-stroke cycle internal combustion engine, a cylinder, a reciprocating piston therein, valyes for admitting fuel at two spaced pointsadjacent one end of the cylinder, means connected to one of said valves for supplying therethrough to the cylinder a stratum of areadily combustible fuel mixture, means connected to the other of said valves for supplying there,-

through to the. cylinder a stratum of a fuel mix-' ture embodying a greater proportion of fuel, ports for admitting and exhausting scavenging air to and from the cylinder under control of the piston, means utilizing an external surface of said piston for providing a supply of air under pressure, a passage for conducting such air into said readily combustible mixture to form a part thereof, and an intake port for said passage adapted to be closed and opened by a portion or the piston spaced from the. piston face.

4. In an internal combustion engine, a cylinder, a reciprocating piston therein, a chamber for receiving a combustion medium, an air compression space, a passage for connecting said chamber and compression space, means whereby the piston on a compression stroke draws air into said compression space and combustion medium into said chamber and whereby said piston on its expansion stroke compresses the air in said compression space and forces air therefrom into said passage toward said chamber thereby applying pressure to the combustion medium in said chamber, and means whereby approximately at the termination of the expansion stroke the piston opens an exhaust port and closes said passage from access to said compression space and combustion medium'is admitted from said chamber to the upper portion of the cylinder, and air from said space is admitted to the lower portion of said cylinder.

5. In an internal combustion engine, a cylinder, a reciprocatingpiston there'in, a chamber for receiving a combustion medium, an air compression space, a passage for connecting said chamber and space, means whereby the piston on a compression stroke draws air into said space and-combustion medium into said chamber and whereby said piston on its expansion stroke comengine, an explosion chamber with a reciprocating piston therein, means including an intake port adjacent one end of the chamber tor introducing air under pressure, means iorconcurrently discharging products of combustion mm the chamber, including an exhaust port adjacent said end but spaced from said intake port, said ports being closed by the piston except when the piston is adjacent its extreme position at said end, means for introducing gas or a rich gas into a zone adjacent the-other end of the chamber when the piston is adjacent the first named end of the chamber, means for then also introducing a gas mixture highly favorable to combustion into a secondzone adjacent said first named zone in the chamber, ignition meanslocated in said second zone and actuated when the piston has compressed the gas and gas mixtures in said zones, the means for introducing the mixture to said second zone including an ,air or gas compression space at the external face of the piston, a passage from said space to the point of admission of the mixture to said second zone, and a port for interconnecting said space and passage, said last named port being closed by the piston when the piston is adjacent the first presses the air in said space and forces air there-' named end or the chamber.

7. In an internal combustion engine, an explosion chamber with a reciprocating piston therein, means including an intake port for introducing air under pressure into said chamber at the termination of an expansion stroke of the piston, means for concurrently discharging products of combustion from the chamber, including an exhaust port spaced from said intake port,

sage irom said space to the point of admission oi the mixture to said second zone, and a port for interconnecting said space and passage, said last named port being closed by the piston when approximately at the end of its expansion stroke.

HEWITT A. GEHRES.

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