AU602282B2 - Stratified air scavenging in two-stroke engine - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION 6Form Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: This document contains the amendments made under Section 49 and is correct for printing Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: G-harles Henry TUCKEY 4681 SCHWEGLER ROAD CASS CITY MICHIGAN 48726

*USA

vj re, Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

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Complete Specification for the invention entitled: STRATIFIED AIR SCAVENGING IN TWO-STROKE ENGINE The following statement is a full description of this invention including the best method of performing it known to me:i 1 Title STRATIFIED AIR SCAVENGING IN TWO-STROKE ENGINE Field of Invention This invention relates to two-cycle engines. It has particular but not exclusive application to two-stroke cycle engines designed with throttle control or exhaust gas and stratified air and fuel intake.

Background and Objects of the Invention In known two-cycle internal combustion engines, it has been standard practice to introduce air and fuel Sinto the crankcase of the engine and transfer it to the firing chamber of the cylinder through transfer ports along the side of the cylinder. This transfer takes place as the exhaust gases are exiting the cylinder, Thus, the o fuel and air are being forced from the crankcase by the pressure created by the descending piston. Air is throttled into the crankcase which can result in a power 0000 loss and a decrease in efficiency.

0000 o 00 00 0 a as Reference is made to a publication of the 0 0 6 000D Society of Automotive Engineers, Inc., No, 790,501, presented at Congress and Exposition, Cobo Hall, Detroit, a'.

0 Michigan, February 26-March 2, 1979, entitled "Active Thermo-Atmosphere Combustion-A New Combustion Process for Internal Combustion Engines" by Shigeru Onishi et al.

Reference is also made to Japanese Patent Preliminary Publications as follows: 54-289816 Marcu 3, L_ 0 1 VA C -1 A- 1 1979 (Application 52-94133, Filed Aug. 8, 1977, Inventor Shigeru Onishi) and 47-23708 Oct. 13, 1972 (Application 46-13382, Filed March 11, 1971, Inventor Shigeru Onishi).

The above-referenced material indicates the advantages and explains the combustion process of stratified charges of exhaust gases and fuel and air mixtures including the throttling of exhaust gases.

According to the present invention there is provided a two-cycle engine having a cylinder, a cylinder head having a fuel and air inlet port, a cylinder wall, a piston in said cylinder, a spark plug in said cylinder 00 0 O no head, and a crankcase, comprising: 0 So a first unidirectional air inlet into the 0 00 o0o o crankcase, "U a transfer passage for air from the crankcase to said inlet port in said cylinder head, a unidirectional valve between the crankoase and said transfer passage, allowing flow from the crankcase to said passage, 0 0uuo means in said transfer passage to inject fuel into air moving through said passage, a one-way valve positioned in said fuel and air inlet port operable to clo.se during the compression phase of said engine, means associated with said inlet port ir, said cylinder head to impart a swirling motion to air and a fuel-air mixture passing trough said inlet port into said cylinder to create a stratification of residual exhaust gases, air, and a fuel-air mixture, L -2an exhaust passage in said cylinder wall, and a throttle means in said exhaust passage to control directly the outlet of exhaust gases and indirectly the quantity of air and fuel-air mixture entering the cylinder, whereby the power level of the engine is controlled.

According to the present invention there is further provided a method of operating the two-cycle engine of the present invention in which the throttle is adjusted to a position to control the quantity of exhaust gas discharged from the cylinder and the means to inject o fuel is actuated to discharge fuel into said transfer c 0 a o passage subsequent to the passage of a quantity of air 094 through said passage during a downstroke of said piston to o 8 oo achieve a stratification of a quantity of exhaust gases, a 0 88 quantity of air and a quantity of fuel-air in said cylinder prior to ignition.

j 0 4 0oo Brief Description of the Drawings I 00 a In order that the invention may be more fully described, an embodiment of the invention will be described by way of example only with reference to the accompanying drawings in which: Fig, 1, shows a vertical section of a diagrammatic illustration of a two-cycle engine illustrating an embodiment of the invention, -3- L' Fig. 2, is a sectional view on line 2--2 of Fig.

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Fig, 3, is a sectional view on line 3--3 of Fig, 1.

Figs. 4, 5 and 6 are similar views showing varying stages of fuel mixture relative to throttle positions.

Detailed Description of A Preferred Embodiment of the Invention With reference to the drawings, Fig. 1 is a diagrammatic illustration of an embodiment of the two-cycle engine of the invention in vertical cross-section. A crankcase 30 flanged at 32 supports a flange 34 of a cylinder jacket 36 having a closed top 38 in which is mounted a spark plug 40. An engine cylinder 50 has an open end 52 exposed to the crankcase 30 and a cylinder head 54 at one side of which the spark plug 40 is screwed into a boss 56.

The cylinder head 54 has a central opening 58 below which is mounted a cage 60 having side openings 62 and a concave central recess 64 opened and closed by a check valve plate 66. The plate 66 is confined for vertical motion to close the opening 58 in the cylinder head in response to pressure within the cylinder Within the cage 60, as shown in Fig. 3, are curved 4, 4 *04 4 4J~ 4,P 0-1 0 4? 04 4 r 0 4 oL 0046 0 4 4444 00&4 0 9 0 41 04 4 -3Ablades 68 which impart a swirling motion to the incoming air and the incoming air and fuel. The cage 60 and the valve plate 66 and fins or blades 68 are made of heat resistant metal which can withstand the heat of the fuel firing during combustion cycles.

In the annular chamber between the jacket 36 and the exterior of the cylinder wall 50 are spiraled baffle turns which form a spiral path 72 from the crankcase at 73 to the chamber 74 above the cylinder head 54. A reed valve 76 is located at the entrance to the spiral passage 72 arranged to pass air from the crankcase to the passage.

The cylinder 50 has a piston 80 slidably mounted in the cylinder 50 with a standard piston rod 82 and crank 84.

An air inlet port tube 90 opens to the crankcase at 92 and a double or quadruple reed valve 94 provides the oneway control on the air inlet.

As illustrated in FIGS. 1 and 2, the cylinder wall is ported at 100, 102 and 104 with short tubes leading to an exhaust chamber 106 which narrows to a throttle passage 108 in which is mounted a throttle plate 110 mounted on a control shaft 112.

Just above the entrance 73 to the spiral passage 72 is a fuel injector 120 which is electronically actuated to inject fuel into the spiral passage. The direction of swirl in the passage 72 imparted by the baffle turns 70 is the same as the L Irrrc--p-sr~Lurr**uwWCL-rl direction of swirl which will be imparted by the blades 68 in the cage Cranking the engine will bring the piston 80 up and down in the cylinder 50. Air will enter the crankcase 30 as the piston rises and will move up into the spiral passage 72 past the reed valve 76 as the piston lowers. This air movement is caused by the lowering of the pressure in the cylinder as the piston moves down and the rise in pressure in the crankcase as the piston moves down. Also, as the piston again descends, 0 fuel is injected into the spiral passage 72 and the combined r fuel and air charge is delivered into the combustion chamber.

S During the up movement of the piston, the charge is compressed.

The firing of the spark plug ignites the mixture during the up compression stroke of the piston and the cycle repeats.

4 As the piston descends during firing, the exhaust Sports 100, 102, 104 are opened as the top of the piston passes 4 4 them and exhaust gases will exit to chamber 106 and passage 108.

I As indicated, near the end of the downstroke, the exhaust ports will be exposed, and, depending on the position of the throttle valve, air and air and fuel mixture will enter the cylinder in a measured volume. If the throttle is wide open, the exhaust gases will be mostly expelled by the layer of incoming air. Thus, the s,'rling charge of incoming air, above which is the air and fuel mixture, serves as a stratified layer essentially in the form of an air piston.

The fuel and air distribution in the cylinder will be stratified in that air from passage 72 will reach the port 58 and enter the cylinder first. As the fuel injector is actuated it will discharge fuel into the air in passage 72.

Thus, a mixture of fuel and air will follow the first air charge and will then reach the cylinder. The fins or blades 68 in cage will impart a further swirling action to the air and the fuel and air mixture which is coming from the spiral passage 72. Since the fuel is heavier than air, it will move to the outside centrifugally in the region of the spark plug where it will be ignited. There is then a stratified charge above the piston in the form of air above which is a mixture of air and 48 fuel. The exhaust gases will impart heat to the incoming 04' charge, and, depending on the position of the throttle valve, 4 will be present to some degree in the charge to be compressed upon the up-stroke of the piston.

a4 0In FIGS. 4, 5 and 6 various stages of a fuel charge ol Sare illustrated. In each case, the piston 80 is shown in the o0 4 down position just prior to the rising compression stroke. In FIG. 4, the throttle is shown in a wide open position. In this circumstance, there is a small residual exhaust gas layer 130 4 and a large volume of air and fuel which can be stratified as above described into air and a mixture of air and fuel. The exhaust gas is practically completely scavenged. Because of the timing, no fuel escapes into the exhaust passages as is common in the standard two-cycle engine since a charge of air precedes the introduction of fuel. Also as described, the air and fuel-air mixture is swirling to insure stratification and complete combustion.

Is a 0 06 00 0 00E 0 0 00 a a In FIG. 5, when the throttle 110 is partially closed, there is a larger volume of exhaust gas 132 retained above the piston because the partially closed throttle has restricted the escape. Above this residual exhaust gas is the air charge and the fuel-air mixture. There is no restriction by throttling of the incoming air (in contrast to the standard engine), and, accordingly, there is no loss of power due to pumping action of the piston. When the exhaust gas is throttled down, there is a reduced combination charge which results in a lower engine output.

In FIG. 6, the throttle 110 is in closed or idle position which allows some escape of exhaust gases. In this condition, there is a large quantity of exhaust gas 134 in the cylinder and a smaller quantity of air and stratified fuel-air mixture. There is only enough air in the mixture to keep the engine running but still a high concentration of fuel-air mixture at the ignition point. In each case the check valve 66 at the cylinder head closes during the compression phase and ignition phase to insure full power to the piston in the down travel.

In addition to the throttle control at the exhaust, there is added advantage in the system in that the air and fuelair mixture spirals around the cylinder 50 to cool it by transmission of heat to the passing air but also the air and fuel-air mixture are preheated by passing the cylinder wall to enhance the combustion characteristics. Thus, the spiral passage 72 insures thorough mixing of the fuel and air but also provides a preheat. The swirling action of the spiral passage 7n is increased by the fins in the cage 60 to insure the desired stratification of air and fuel-air entering the cylinder and

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i the movement of the fuel to the outer areas adjacent the spark plug.

The result of the combined action of the various elements described is a more complete combustion, reduction of undesirable exhaust gases, and increased engine efficiency. No external cooling apparatus such as a fan or a coolant pump is required, and also there is no intake air throttling as exists in a standard cycle engine to cause pumping losses in the engine.

The engine can operate primarily on auto-ignition except at full throttle when normal spark plug ignition would function.

The engine is also adopted to use with fuel mixtures in addition to operation with stanrdard gasoline.

The embodiment has been advanced by way of example only and modifications are possible within the scope of the invention.

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Claims (7)

1. A two-cycle engine having a cylinder, a cylinder head having a fuel and air inlet port, a cylinder wall, a piston in said cylinder, a spark plug in said cylinder head, and a crankcase, comprising: a first unidirectional air inlet into the crankcase, a transfer passage for air from the o crankcase to said inlet port in said cylinder head, a unidirectional valve between the crankcase and said transfer passage, allowing flow from the crankcase to said passage, means in said transfer passage to inject fuel into air moving throligh said passage, i a one-way valve positioned in said fuel and 0o air inlet port operable to close during the compression o0 phase of said engine, means associated with said inlet port in said cylinder head to impart a swirling motion to air and o a fuel-air mixture passing trough said inlet port into said cylinder to create a stratification of residual exhaust gases, air, and a fuel-air mixture, an exhaust passage in said cylinder wall, and a throttle means in said exhaust passage to control directly the outlet of exhaust gases and indirectly the quantity of air and fuel-air mixture entering the cylinder, whereby the power level of the engine is controlled, -9-

2. A two-cycle engine as defined in claim 1 in which said fuel and air inlet port is positioned in said \i cylinder head substantially concentrically to said cylinder. 3, A two-cycle engine as defined in claim 1 in which said transfer passage encircles said cylinder to cool said cylinder as said fuel injection means introduces fuel into said passage and a fuel-air mixture passes to said cylinder head. A two-cycle engine as defined in claim 1 in which said transfer passage is formed as a spiral passage surrounding said cylinder wall and rising from the crankcase to said cylinder head to impart a swirling action to air and fuel-air mixture ,n the same direction as the means associated with said fuel and air inlet port, 1 5, A two-cycle engine as defined in claim 4 in which said means to inject fuel is positioned to inject fuel in air passing in said spiral passage, 6, A two-cycle engine as defined in claim 1 in which said cylinder is enclosed in a jacket having a wall 59 spaced from the wall of said cylinder, and said transfer passage is formed by spiral divisions between said wall of said cylinder and said wall of said jacket forming a spiral passage originating at said crankcase and terminating at said cylinder head, A^^ &5 L s

7. A two-cycle engine as defined in claim 6 in which said jacket has a closed end covering said cylinder head and spaced therefrom to provide a chamber above said cylinder head to receive air and fuel-air from said spiral passage.

8. A two-cycle engine as defined in claim 6 in which a second unidirectional valve is positioned at the introduction of said spiral passage leading from said crankcase. A two-cycle engine as defined In claim 3 in which said fuel injector is timed to introduce fuel into said passage after a quantity of air has been Introduced into the passage. A two-cycle engine as defined in claim in which said means to impart a swirling motion comprises a plurality of curved fins downstream of said fuel and air inlet port in said cylinder head, and moans to retain said o fins in spaced relation,

11. A two-cycle engine as defined in claim 10 in which said means to retain said fins has a central support o, ,means downstream of said fuel and air inlet port in said cylinder head, and said one-way valve is mounted on said support means to close said fuel and air inlet port during a compression and ignition phase of said engine, -11- _i 1

12. A method of operating the two-cycle engine as defined in claim 1 in which the throttle is adjusted to a position to control the quantity of exhaust gas discharged from the cylinder and the means to inject fuel is actuated to discharge fuel into said transfer passage subsequent to the passage of a quantity of air through said passage during a downstroke of said piston to achieve a stratification of a quantity of exhaust gases, a quantity of air and a quantity of fuel-air in said cylinder prior to ignition, 13, A two-cycle engine substantially as hereinbefore described and illustrated with reference to the 0 o o accompanying drawings. 0 0

14. A method of operating a two-cycle engine O 0 oo substantially as hereinbefore described and illustrated with reference to the accompanying drawings, DATED THIS 27TH DAY OF JUNE, 1990. 0o Charles Henry TUCKEY o0, By His Patent Attorneys: o o 00 GRIFFITH HACK CO. Soa Fellows Institute of Patent ooa° Attorneys of Australia. 4 6 I La