US2370456A - Internal-combustion engine - Google Patents

Description

Feb. 27, 1945. A. 'FEROY INTERNAL-COMBUSTION ENGINE Filed March 18, 1944 H-IS A INVENTOR A e ero i'wm 57 y;

Patented Feb. 21,-- 1945.

.v m-reo STATES PATENT OFFICE] 2,370,456 INTERNAL-COMBUSTION Enema Arne Feroy, New York, N. Y. Application March s, 1944, Serial No. 527,063

' 7 Claims;

This invention relates to internal combustion engines and its object is to provide a simple engine of low cost, capable of high specific P rformance.

The simplest engine is the two-stroke cycle with crankcase scavenging. It has no valves and no separate blower--no moving parts for pump or any additional parts or manufacturing cost.

The work needed for scavenging is less than with any engine having a separate blower or scavenging pump. For example, to drive a rotary blower may require about 17% of the engine power, which amount would. therefore not be available at the engine shaft. And of this power required to drive the blower, only about half would actually move air, the other half being dissipated in mechanical and other'losses of the blower and its drive. Most rotary blowers have the "square indicator card, showing about twice the work needed to move the same air by a piston compressor. All things considered, the work done in .scavenging an engine by a. separate blower is about twice that done by crankcase scavenging.

The saving is available at the shaft of the I crankcase scavenged engine to increase its net output, and in manufacture, the cost of the separate blower is also saved.

One disadvantage of the crankcase scavenged engine has been its inability to develop more than about 45 lbs/sq. in. BMEP. To get high specific performance, it is necessary tohave-complete scavenging, requiring a volume of air about 140% of the piston displacement, but the crankcase scavenged engine has only 100% of its piston displacement for pumping purposes, and with the losses usually present, it realizes only about 70% of that. Consequently it gets about half the air it ought to have for high performance. An object of this invention is to provide means for increasing the air flow thru the engine to what it should be for high performance, without adding, complication to the engine. In other words, an object is to make a simple crankcase scavenged engine supercharge itself-to make the pumping action of the under side of the piston put more air into theengine than the piston displacement.

In the drawing, Fi 1 is a transverse sectional view of an engine constructed in accordance with the invention; Fig. 2 is a similar view of a portion of the engine showing a modification of the structure; Fig. 3 is a crankcase indicator diagram of an ordinary three-port engine; and Figs. 4 and 5 are crankcwe indicator diagrams of engines constructed in accordance with the invention.

Referring to Fig. 1, the engine may be of wellknown three-port two-stroke type, comprising cylinder casting 6 closed at the top by cylinder head I and at, the bottom by oil pan 8. Piston I is operable in the usual manner, being connected by connecting rod ii to, crankshaft l2.

Piston I0 is shown in top center position. Pis-. ton l0 may be said to divide the space between cylinder head i and oil pan 8 into two chambers, the cylinder or working chamber 8 above the piston, and the crankcase or pumping chamber I9 below the piston.

Piston l0 overruns inlet ports i8, bypass ports 2!, and. exhaust ports 22, in the usual manner, 20 well-known in three-port engines. Inlet ports l8 load from intake pipe H of considerable length.

Bypass ports 2! lead from bypass 20 connecting" pumping chamber IS with working chamber 9.

Exhaust ports 22 lead out of working chamber 9 to exhaust pipe 28.

If more freedom is desired in controlling the tim of inlet ports into pumping chamber 58,

inlet pipe Ila, Fig. 2, may open directly thru ports Illa intdpumping chamber l9, controlled by port IS in a rotating web member on cranmhaft E20,.

Operation of the engine on the two-stroke cycle, either Otto or Diesel cycle, is well understood. As a Diesel, piston M), on the upward stroke compresses a charge of airin working 35 chamber 9 sufiiciently to ignite the fuel when injected, and the resulting combustion drives piston l0 downward until ports 22 are opened,

- permitting the products of combustion to exhaust. I

This invention is concerned more with the pumping' action in chamber l9.

In Figs. 3, 4, and 5, S is the stroke of piston I0, and the dot-dash line A indicates atmospheric pressure. Heights of ports [8 and 2| are denoted Hl8 and H2l respectively.

4 For comparison with the improvements of the invention, Fig. 3 shows the pumping action in the crankcase of an ordinary three-port twostroke engine (without pipe I! and with the ordinary short bypass connecting chambers I9 60 and 3 thru ports 2|, the bypass only just long enough to get around piston I, as usual). Piston If], on its upward stroke toward top center in which it is shown, creates a depression in crankcase chamber I9 until ports l8 open, when II the depression is partially satisfied, but the preswhen ports l8 close.

around the piston thru a short bypass into working chamber 9. When ports 2| are closed by piston ID, the pressure inpumping chamber I9 is still above atmospheric by the amount 32, so that piston It has to go further upward to reduce the pressure below atmospheric, to induce another charge of air to enter when ports |8 open again.

The pumping is inefficient at both ends of the stroke. The suction stroke starts from a pressure above atmospheric, and the pressure stroke starts from a pressure below atmospheric.

Conditions at one end of the stroke can be improved by the addition of a long enough inlet pipe l1. Fig. 4 shows pumping action in an engine with inlet pipe l1 and the ordinary short bypass connecting chambers l9 and 9 thru ports 2|. Piston III, on its upward stroke toward top center, creates a depression in crankcase chamber I9, as before, until ports I8 open, when air rushes in thru pipe |I, and the inertia of the column of air in pipe I! forces more air into the crankcase, producing the overpressure 4| Crankcase compression starts from above the atmospheric line A building up to higher pressure during the downward stroke of piston MI, so that when ports 2| open, more air flows into cylinder 9. And yet, because the bypass is short, there is still an overpressure 42 in pumping chamber I9 when ports 2| close. Piston ID has to go part way upward before pressure inchamber Is is reduced'to atmospheric. The suction stroke starts. inefficiently as before. Conditions have been improved at one end of the f pumpingstroke but not at the other.

, sion in crankcase |9..unti1 ports l8 open, when air rushes in'thru pipe l1 and ports I8, buildin up velocity in the column of air in pipe so 'that the inertia of the column forces more air into chamber l8, producing overpressure 5| when ports l8 close. Crankcase compression starts cific performance almost twice that usually possible with ordinary crankcase scavenging.

While specific embodiments of the invention have beenshown and described it is understood that changes may be made in the arrangement and in the construction of the various parts, without departing fromthe spirit or scope of the invention as expressed in the following claims.

I claim:

.1. ma two-stroke engine having a cylinder and a crankcase with a piston operable therebetween, a port opening into said crankcase, means delaying the opening of said port until said piston has nearly completed its upward stroke, and a conduit opening into said port from air at a given pressure and so proportioned as to produce more than said given pressure in said crankcase when said port closes.

2. In a two-stroke engine having a cylinder and a crankcase with a piston operable therebetween, a port opening into said crankcase,

means delaying the opening of said port until said piston has nearly completed its upward stroke, and a tubular passage opening into said port from air at a given pressure such as atmospheric, said passage being long enough relative to the timing of said port to deliver more air to said crankcase and to produce more than said given pressure therein at the closing of said port.

3. Ina two-stroke enginehavin'g a cylinder and I a crankcase with a piston operable therebetween,

a port opening into said crankcase, means delaying the opening of said port until said piston from above atmospheric pressure, building up a higher pressure, so that when ports 2| open, more air flows into cylinder 9 thru long bypass 20, which in turn builds up velocity. The inertia of the column of air in long-bypass 20 sucks more air out of crankcase l9, producing underpressure 52 therein by the time ports 2| close. .Thus when piston Ill starts upward on its suction stroke, there is already less than atmospheric pressure in crankcase chamber l9. Consequently the de-. pression is greater than before, when ports l8 open. The pumping efflciency is improved at both ends of the'stroke of piston l0, and its becomes possible to induce more air to flow thru the has nearly completed its upward stroke, a conduit opening into said port from air at-a given pressure and so proportioned as to producemore than said given pressure in said crankcase when said port closes, a port opening into said cylinder from said crankcase when said piston. has nearly completed its downward stroke, and means associated with said last-named port and producing less than atmosphericpressure in said crankcase when said last-named port closes.

4. In atwo-stroke engine-havinga cylinder and a crankcase with a piston operable therebe-. tween, a port opening into said crankcase,

means delaying the opening of said portuntil said piston has nearly completed its upward stroke, a 'pipe of such length leading to said port as to produce more than atmospheric pres-- sure in said crankcase when said port closes, a port opening into said cylinder when said piston has nearly completed its downward stroke, and a pipe of such length connecting said last-named port with said crankcase as to transfer more air .from said crankcase to said cylinder and to reduce the pressure in said crankcase to less than atmospheric when said last-named,port closes.

5. A three-port two-stroke engine having 8. cylindex and a crankcase with a piston operable therebetween, one port opening into said crankcase and uncovered by the lower edge of said piston when nearing top center, a pipe'opening into said port, fromair at a given pressure and so proportioned as to produce more than said given pressure in said crankcase when said port closes,

a second port in said cylinder uncovered by the pper edge of said piston when nearing bottom center, a bypass connecting said second port with said crankcase, and a third port in Said cylinder opening outwardly to exhaust said cylinder as said piston approaches bottom center.

6. A three-port two-stroke engine having a cylinder and a crankcase with a piston operable au os therebetween. one port opening into said crank case and uncovered by the lower edge of said piston when nearink top center, a pipe of considerable length opening into said port; a second port in said cylinder uncovered by the upper edge of said piston when nearing bottom center, a pipe of considerable length open1n8 into said second port from said crankcase, and a third port in said cylinder opening outwardly to exhaust said cylinder as said piston approaches bottom center.

7. A three-port two-stroke engine having a cy'1-' inder and a crankcase with a piston operable therebetween and three ports controlled by said piston, one opening into said crankcase; the

second openins into said cylinder from said crankcase, and thethird openins outwardly from said cylinder: the combination ot a 'pipe lead- AIR-NE FEROY.

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