Internal-combustion engines – Two-cycle – Rear compression
Reexamination Certificate
2000-01-10
2001-12-11
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Two-cycle
Rear compression
C123S0650PE, C123S0730CA, C123S0730SC, C123S1960CP, C184S006800
Reexamination Certificate
active
06328004
ABSTRACT:
INTRODUCTION
The present invention relates to internal combustion engines.
Diesel fuel is environmentally much more acceptable than petrol and two stroke engines by their very nature are more advantageous than four stroke engines since theoretically for identical speeds a two stroke engine should produce twice the output of a four stroke engine. This is obviously not the case for many reasons and further two stroke engines are environmentally unacceptable in that they are a major source of pollution, as It is estimated that somewhat of the order of 40% of the oil/fuel mix which is used to lubricate the engine is delivered unburnt to exhaust. Increasingly stringent exhaust emission regulations in many countries will in effect prohibit the use of conventional two stroke engines.
A further problem with many engines is that they operate in corrosive or otherwise unsuitable environments. It is appreciated that compression ignition engines are more efficient than other types of internal combustion engines particularly in such situations. They are also particularly suitable for continuous running. One of the problems with the use of compression ignition engines for low horsepower outputs is that they are generally extremely heavy. For example, it is not unknown for a conventional compression ignition engine producing somewhat of the order of 6 horsepower to have a weight in excess of 136 kg (300 lbs). Such an engine is generally speaking of limited use except for stationary applications. Further, because it is so heavy it is relatively expensive to produce, uses a considerable amount of material and is difficult to transport. Thus, diesel engines by their nature are unsuitable for many uses such as relatively small machines, for example, lawn mowers, marine outboard engines, portable generators and hand tools.
In summary, there are considerable advantages in having a slow revving compression ignition engine if such a slow revving compression ignition engine could be relatively lighter than heretofore.
Further, it is advantageous to have an efficient lubrication-system, particularly for two stroke engines which does not suffer from the disadvantages of the present system using a combination of oil and fuel which is an inefficient way of carrying out the lubrication, doesn't operate during idling conditions with the throttle closed and further is a major source of pollution.
Ideally any such internal combustion engine if its weight is to be reduced must incorporate an efficient air charging system and further should, if possible, have an efficient supercharger. Unfortunately conventional superchargers are expensive and relatively wasteful of power input. Further in many instances they require lubrication which leads to added pollution. It has long been appreciated that air charging by under-pumping or, as it is often referred to as crankcase scavenging, is efficient, but heretofore because of the general size of sumps, etc. has not been particularly efficient.
It has further been long appreciated that the use of an injector such as described and claimed in Irish Patent No. 69,966 hereinafter the-Rynhart pneumatic injector so named in honour of its inventor is a very efficient way of delivering diesel fuel to a compression ignition engine and is particularly useful with engines of low power output as the weight saving in the pneumatic injector compared to a conventional pump and injector system is significant. Therefore there is a need for an engine which will efficiently use the Rynhart injector.
One of the problems with the use of a supercharger in a compression ignition engine and in particular in a compression ignition engine which utilises a pneumatic injector, such as the Rynhart pneumatic injector, is the need to control the compression pressure in the engine accurately for efficient combustion.
It has been appreciated that there are problems in having flywheels of conventional construction in that when piston seizure occurs, considerable damage can be done with the flywheel shearing and causing damage.
Further, it is known that one of the major problems with all internal combustion engines is the use of hydrostatic bearings which add to the cost of the engine and which require high pressurised lubrication systems. Anything that could obviate the need to use such hydrostatic bearings and for example allow the use of frictionless bearings would be advantageous.
OBJECTS OF INVENTION
The present invention is directed towards providing an internal combustion engine that will overcome some of these drawbacks in the present constructions of engines and is particularly directed towards providing an efficient compression ignition two stroke engine that will produce more power output than a much higher revving four stroke engine of the same weight.
SUMMARY OF INVENTION
The invention provides an internal combustion engine with under piston charging and a positive displacement supercharger outside the air charging chamber formed underneath the piston in the crankcase of the engine. The positive displacement supercharger comprises a supercharger housing mounting a diaphragm in the housing which diaphragm divides the housing into a front delivery chamber communicating via an outlet with an air inlet duct in the casing forming the air charging chamber and a rear chamber open to the atmosphere. The diaphragm can be moved across the chamber towards the outlet in a working stroke delivering air into the engine and away from the outlet in a return stroke drawing air into the housing. The diaphragm is supported on a piston formed from a plate having a hole which is slidably mounted on the crankshaft. A one-way valve is mounted in plate and a cam assembly is provided for reciprocating the piston on the crankshaft. The cam assembly comprises a cam connected to the piston and a rigidly mounted cam follower. A timed delivery valve is provided between the supercharger and the charging chamber in the air inlet duct between the supercharger and the charging chamber. The timed delivery valve is opened at approximately BDC and closed after the air transfer port in the cylinder bore which communicates with the air charging chamber of the under-pumped IC engine is shut off.
The invention provides various inserts of structured foam plastics material such as polyurethane to reduce the volume of the charging chamber.
In one embodiment, the invention provides a generally cylindrical bob weight for the connecting rod of the engine filled with inserts to again reduce the volume of the charging chamber.
Further, the invention provides a lubricant distribution assembly which comprises means for delivery of oil from the oil storage sump of the engine and means for injecting oil between the piston skirt and cylinder wall at discrete time intervals. Further, there is provided scavenging means for removing oil from the piston skirt and cylinder wall and returning excess oil to the sump through lubricant galleries comprising enclosed passageways. In this way, the excess oil is not burnt off in the engine but is removed from the piston skirt and cylinder wall. The galleries communicate through the piston and connecting rod to the sump. Oil is injected between the piston skirt and the cylinder wall by an oil pump which delivers oil from the oil storage sump out through the cylinder wall which then directs the oil against the piston. There can be a number of circumferentially spaced holes around the cylinder wall for the injection of oil onto the piston. The piston will generally have a circumferential groove in the piston skirt to receive the oil. An additional elongate axially arranged groove in the piston skirt may communicate with the hole in the cylinder wall and with the circumferential groove in the piston skirt.
It will be appreciated that as the piston reciprocates, the axially arranged groove will at certain times coincide with the hole in the cylinder wall.
Ideally, the circumferential groove in the piston incorporates an oil scavenging ring and is preferably adjacent the bottom of the piston skirt.
Gallerie
Jacobson & Holman PLLC
Kamen Noah P.
Rynhart Research and Development Company Limited
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