AU663377B2

AU663377B2 - Improvements to two stroke engines

Info

Publication number: AU663377B2
Application number: AU39868/93A
Authority: AU
Inventors: John Patrick Ettridge
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-05-28
Filing date: 1993-05-28
Publication date: 1995-10-05
Anticipated expiration: 2013-05-28
Also published as: AU3986893A

Description

P/00/Oil1 28/5/91 Regulation 3.2 AUSTRALIA LZ m Pate nts Act 1990 1

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: f& Y 12 4C Th foillowing statement is a full description of this invention, including the best method of performing it known to me:t 0 6 0$ 06

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1 IMPROVEMENTS TO TWO STROKE CYCLE ENGINE p n Da

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a o 6 a a~ a The object of This invention is to improve the inherit problems of the simple two stroke side porting designed engine, which are the oil having to be mixed with the fuel for lubrication, 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. Then the burning of the oil with the air fuel i0 mixture. In the normal two stroke engine the crankcase pressure is to low for an effective exhaust muffler or noise inhibitor to be fittted. All t:he above design problems have resulted in the 0 simple two stroke engine getting a reputation as a noisey, uneconomical, air polluting engine.

S This invention allows some of the exhaust gases from above the piston to escape through a filter to remove the solid particles in .O the exhaust gases into the crankcase before the main exhaust port opens. This has the effect of raising the crankcase pressure, allowingfilters to be fitted in the transfer channels to restrict the oil, and only allow the air fuel mixtu.re to pass into the combustion chamber ensuring a more effective combustion and S detonation of the air fuel mixture.

S This increased transfer pressure makes it possible bo have a wet sump crankcase, and only air fuel, not oil fuel mixture to come through the carburetor. It also makes it possible to fit an 30 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.

00 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 fuiel economy and lower levels of air pollution. The standard fuel used in Two Stoke engines is unleaded, resulting in a further reduction in air pollution.

This invention in its simplest form consists of the excepted two stroke engine. Fig.1. a piston 7, cylinder 5, crankshaft 11, crankcase 1, transfer port 4, exhaust port 3, and fuel inlet 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, plus the length of the piston skirt and diameter of the port. a filter 14, is fitted in the channel to remove solid particles of exhaust gases. Th=re a.re oil. filters 16 fitted in the transfer channel 4. to prevent the oil in the air fuel mixture from leaving the crankcase, and being burnLt in the combustion chamber. The oil 15.removed from the air fuel mixture is returned to the crankcase The transfer channel 11. in the cylinder wall 5 .is positioned so that as the top of the piston 8 opens the tranfer channel 11 in the cylinder wall 5 to the exhaust gases the skirt of the piston 7 is nearly at the bottom of the transfer channel 11.

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

Alternatively the additional channel 11. may be opened and closed by a port in the piston wall 12.

Those skilled in the art will realize that by varying the position, size and length of the ports 12. or transfer channel 11 1 0 in the wall of the cylinder 5 it is possible to give predetermined timeing for the opening Fig 3 and closing Fig 4 of the channel 11.

or transfer groove 11. Usually the "timing"employed has to be a compromise. It can only be absolutely right for one particular o, speed, which means that it is less efficient at others.

j 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 cy] inder S Fig 2. 45 degrees rotation of crankshaft 13. The fuel inlet closes S compressing the new fuel charge in the crankcase 1.

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

Fig 4. 115 degrees rotation of crankshaft 13. The transfer channel 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 e!0 escape into the cylinder 5 above the piston 7. At this point both S' the transfer port 4 and the exhaust port 3 are opened.

Fig 6. 180 degrees rotation of crankshaft 13 or bottom dead Scen.ire. The transfer port 4 is fully open, Fig 7. 235. degrees rotation of crankshaft 13. The transfer port 4 closes Fig 24t5 degrees rotation of cra.nksha1t 13. The exhaust port 3 closes and the transfer channel 11 is about to open.

Fig 9. 255.,degrees rotation of crankshaft 13. The transfer channel 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 is ignited continuing the cycle.

i -m 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 0 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 design and performance S requirements.

o[o Fig 11. The top of the piston 8 is closing off the transfer 0000, channel 11 even though the opening 12 in the skirt of the piston 7 is open allowing the gases in the crankcase 1 to flow into the transfer channel 11.

0 Fig 12. The gases can flow from above the piston 8 down the 0 transfer channel 11 into the crankcase 1.

now closed the bottom of the transfer channel 11 preventing the flow of gases.

Fig 14. Fig 15. Fig 16. Show the transfer channel 11 using the bottom of the piston skirt 9 to open and close the transfer channel 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 channel 11. This may present a problem at slow speeds, Fig 14. The top of the piston 8 is closing off the transfer channel 11 even though the bottom of the piston skirt 9 is open to the transfer channel 11 allowing the gases ,to move freely between the crankcase 1 and transfer channel. 1., Fig 15. The gases can move freely from above the piston 8 into the Scrankcase 1 through the transfer channel 11.

Fig 16. The bottom of the skirt of the piston 9 has closed off the transfer channel 11 even though the gases can move from above the pisto n 8 into the transfer channel 11.

Fig 17. shows a possible oil filter 16 of wire gauze held in the transfer channel 4 with a removable backing plate 17 so the filter 16 can be removed or cleaned. This is only one of the possible types of oil filters that could be used.

Claims

1. A two stroke reciprocating-piston in-cylinder crankcase aspirated side porting engine with an oil filter fitted in the fuel air transfer channel to prevent the oil moving into the combustion chamber and being burnt, the oil is returned to a wecL sump in the crankcase, there is also an additional porting arrangement which opens and closes to allow some of the e,:haust 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 unburnt fuel and air polluting gases escaping into the atmosphere, through an exhaust muffler or noise inhibitor, the engines higher crankcase pressure enabling the use of mufflers and noise inhibitors with higher back pressures than other engines are capable of using.

2. A two stroke reciprocating-piston in-cylinder crankcase aspirated side porting engine with oil filters fitted in to the air fuel transfer channel to prevent the oil moving inbo thi combus.ion cnamber and being burnt, the oil is returned to a wet sump in the crankcase. rRA4 x is 04