AU657315B2

AU657315B2 - Improvements to the two stroke cycle engine

Info

Publication number: AU657315B2
Application number: AU14009/92A
Authority: AU
Inventors: John Patrick Ettridge
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-04-03
Filing date: 1992-04-01
Publication date: 1995-03-09
Anticipated expiration: 2012-04-01
Also published as: AU1400992A

Description

P/00/01 1 2WW0/1 AUSTALIARegulation 3.2 Patents Act 1990 ORIGINAL 6573 COMPLETE SPECIFICATION STANDARD PATENT Invention Title: To trk nyl F ie *o 0 0 following statement is a full description of this invention, including the best *.vithod of performing it known to me:pe attatched, p!age 1 I. 1. IMPROVEMENTS TO THE TWO STROKE CYCLE ENGINE The object of this invention is to improve the inherit problems of the simple two stroke side porting designed engine, which are low crankcase pressure, poor transfer of the new fuel charge to above the piston, ineffective scavenging, or removal of the exhaust gases, some of the new fuel charge being swept out with the exhaust gases as the exhaust port closes after the fuel transfer port, and air pollution mainly caused by the mixing of oil with the fuel. In the normal two stroke engine the crankcase pressure is to low for an effective exhaust muffler or noise inhibitor to be fitted. All the above design problems have resulted in the simple two stroke engine getting a reputation as a noisey, uneconomical, air polluting engine.

This invention allows some of the exhaust gases from above the piston to escape into the crankcase before the main exhaust port opens. This has the effect of raising the crankcase pressure, ensuring a better transfer of the fuel to above the piston.

eo Promoting better detonating of the air fuel mixture.

20 This increased transfer pressure makes it possible to fit a more o* effective exhaust system for a quieter motor. The "back pressure", the gas flow restrictions created by the more effective exhaust system does not prevent the fuel being transferred from the crankcase to above the piston.

The partial reburning of some of the exhaust gases preheats the new air fuel mixture ensuring better detonation of the fuel mixture resulting in an increase in fuel economy and lower levels of air pollution.

*0 It This invention in its simp)est form consists of the excepted two stroke engine. Fig.l. a piston 7, cylinder 5, crankshaft 13, crankcase 1, transfer port 4, exhaust port 3, and fuel i.nlet port 2, with an additional groove or transfer channel 11, in the wall of the cylinder 5, running from just above the height of the exhaust port 3, to approximately the bottom of the exhaust port 3.

There is a port 12 in the skirt of the piston 7 to line up with the transfer groove 11 in the cylinder wall 5. This port 12 is positioned so that as the top of the piston 8 opens the tranfer groove 11 in the cylinder wall 5 to the exhaust gases the port in the piston 7 skirt is at the bottom of the transfer groove 11. The intention is for the port 12 to allow the exhaust gases above the piston to escape to below the piston 7 and for the transfer port 11 to be closed before the main exhaust port 3 opens raising the air pressure in the crankcase 1.

Alternatively the additional groove may be positioned running from just above the height of the exhaust port 3 in the cylinder wall plus the length of the piston 7. The channel 11 is opened and closed by the top of the piston 8 and the bottom of the skirt of the piston 9.

The intention is for the channel 11 to allow the exhaust gases above the piston 7, to escape to below the piston 7, and for the transfer channel 11 to be closed before the main exhaust port opens 3, raising the air pressure in. the crankcase 1.

Those skilled in the art will realize that by varying the position, size and length of the groove 11 or transfer channel 11 in the wall of the cylinder 5 it is possible t6 give predetermined timeing for the opening Fig 3 and closing Fig 4 of the" groove 11 or transfer channel 11. Usually the "timing"employed has to be a compromise. It can only be absolutely right for one particular speed, which means that it is less efficient at others.

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The new two stroke cycle is Fig 1. 0. degrees or top dead centre. The spark 10 ignites the compressed air fuel mixture forceing the piston 7 down the cylinder Fig 2. 45 degrees rotation of crankshaft 13. The fuel inlet closes compressing the new fuel charge in the crankcase 1.

Fig 3. 105 degrees rotation of crankshaft 13. The Transfer groove 11 opens allowing some exhaust gases to escape into the crankcase 1.

Fig 4. 115 degrees rotation of crankshaft 13. The t'ansfer groove 11 has closed and the exhaust port 3 opens.

Fig 5. 125 degrees rotation of crankshaft 13. The transfer port 4 opens forceing the compressed fuel in the crankcase 1 to escape into the cylinder 5 above the piston 7. At this point both the transfer port 4 and the exhaust port 3 are opened.

Fig 6. 180 degrees rotation of crankshaft 13 or bottom dead centre. The transfer port 4 is fully open.

?ig 7. 235 degrees rotation of crankshaft 13. The transfer port 4 closes Fig 8. 245 degrees rotation of crankshaft 13. The exhaust port 3 closes and the transfer groove 11 is about to open.

Fig 9. 255 degrees rotation of crankshaft 13. The transfer groove 11 closes. The fuel chare is now being compressed above the piston 7.

Fig 10. 315 degrees rotation of crankshaft 13. The fuel inlet is opened by the bottom of the piston skirt 9 and as the piston 7 moves up the cylinder 5 wall the volume below the piston 7 increases sucking the new fuel through the fuel inlet 2 into the crankcase.

At the top of the stroke the new air fuel mixture 1i ignited continuing the cycle.

ee.a 40 1 3 Those skilled in the art will realize the degrees of rotation of the shaft used to illustrate the new cycle can be varied to suit design and performance requirements also it is possible to substitute grooves with ports positioned top and bottom connected by a tunnel or backing plate which allows the gasses to move from one port to the other.

It may be prefered to use more than one transfer groove to suit design and performance requirements.

Fig 11. Fig 12. Fig 13. Show the transfer groove 11 with an opening 12 in the skirt of the piston 7 just below the compression rings 6. This arrangement can be used if the normal two stroke has cutaways in the piston skirt to suit desigrn and performance N requirements.

9@9S Fig 11. The top of the piston 8 is closing off the transfer groove 11 even though the opening 12 in the skirt of the piston 7 20 is open allowing the gases in the crankcase 1 to flow into the "transfer groove 11.

Fig 12. The gases can flow from above the piston 8 down the S transfer groove 11 into the crarikcase 1.

Fig 13. The top of the opening 12 in the skirt of the piston 7 has now closed the bottom of the transfer groove 11 preventing the S" flow of gases.

SFig 14. Fig 15. Fig 16. Show the transfer groove 11 using the bottom of the piston skirt 9 to open and close the transfer groove 11. If there is to much clearence between the piston skirt 7 and the bore of the cylinder 5 exhaust gases may not be retained in the transfer groove 11. This may present a problem at slow speeds.

Fig 14. The top of the piston 8 is closing off the transfer groove 11 even though the bottom of the piston skirt 9.is open to the transfer groove 11 allowing the gases to move freely between the crankcase 1 and transfer groove 11.

Fig 15. The gases can move freely from above the piston 8 into the crankcase 1 through the transfer groove 11.

Fig 1. The bottom of the skirt of the piston 9 has; closed off thtransfer groove 11 even though the gases cti move from above the n't.nn 8 intn thf t.erfer- rnnv,- 11 4 ine ciaims deiining the invention are as follows, 1. A two stroke side porting reciprocating piston in cylinder crankcase aspirated engine with an additional porting arrangement which opens and closes to allow some of the exhaust gases from above the piston to escape into the crankcase before the exhaust port opens, raising the crankcase pressure and preheating the incoming fuel charge, while double burning some of the exhaust gases to reduce unrburnt fuel and air polluting gases escaping into the atmosphere, through a more effective exhaust muffler, or noise inhibitor less effected by the gas flow restrictions common in such devices.

A two stroke reciprocating piston in cylinder crankcase aspirated engine having a porting system which opens and closes to allow some of the exhaust gases from above the piston to escape into the crankcase before the exhaust port opens to raise the crankcase pressure, 0. 0.

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