Internal-combustion engines – Valve – Reciprocating valve
Reexamination Certificate
2002-10-17
2004-01-06
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Valve
Reciprocating valve
Reexamination Certificate
active
06672270
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to internal combustion engines which have one or more power pistons that reciprocate in one or more cylinders. In particular, the invention relates to engines of this type which operate on a four stroke cycle in which the power pistons cyclically undergo fuel inlet strokes, compression strokes, expansion strokes and exhaust strokes. More particularly, the invention relates to inlet valves and valve operating components which admit a fuel and air mixture into the cylinders of engines of this type.
Fuel efficiency may be defined as pounds of fuel consumed per horsepower hour of work delivered. The fuel efficiency of most engines of the above identified type varies greatly as a function of power output or engine speed. Efficiency is highest when the engine is operating at or near its full power output and at a steady speed. Efficiency decreases when the engine is operated at reduced power outputs. Many uses of such engines require that power output be reduced much of the time. This is most notably the case with automobile engines. Automobile engines are designed to provide for occasional periods of high power output. This is needed, for example, to accelerate the vehicle on freeway on-ramps or while passing other vehicles or to maintain speed on an upgrade. Power output is reduced when the vehicle is cruising at a steady speed on a freeway or highway or is slowed by traffic conditions. Power output ceases when the vehicle is temporarily stopped with the engine idling.
The practical result of these factors is that most conventional automobile engines operate with reduced fuel efficiency much of the time. This increases operating cost, unproductively consumes fuel resources and has adverse effects on efforts to reduce emission of pollutants into the environment.
This problem arises in part as the typical automobile engine is designed to have a low compression ratio that provides for optimum performance when the engine operates at or near full power output. A higher compression ratio would provide greater efficiency during the periods when the engine is being operated at reduced power output but, in the conventional engine, the high ratio causes overly rapid fuel burning resulting in detonation or “knocking” at times when the engine must be operated at or near maximum power output. Fuel detonation severely strains engine components, creates unacceptable noise and drastically reduces engine efficiency.
It has heretofore been recognized that more efficient overall operation can be realized by designing the engine to have a compression ratio which varies as a function of engine load. Compression ratio can be high when the load is light as detonation is not a problem under that condition. In engines which operate on the Atkinson cycle, a mechanism is provided which varies the length of travel of the power pistons in the cylinders so that the inlet stroke is much shorter than the power or expansion stroke. Some prior engines have auxiliary pistons which reciprocate in chambers that are communicated with the power piston cylinders. Auxiliary piston movement varies the compression ratio in, response to changes of engine load. The auxiliary pistons take up a substantial amount of space in the combustion chambers. This requires that the inlet and exhaust valves be smaller than would be desirable for optimum breathing capacity. Engines of these prior kinds require bulky additional components which substantially complicate the engine and which are very prone to rapid wearing.
Engines of the Miller cycle type also vary the compression ratio as a function of power output and are not subject to the above described problems. In a Miller cycle engine the effective volume of the cylinders is varied by varying the timing of closing of the fuel inlet valves relative to power piston position. For example, closing of the fuel inlet valve may be delayed until after the intake stroke of the piston is completed and the subsequent compression stroke is underway. Thus actual compression of the fuel charge does not begin until some time after the compression stroke movement of the piston has commenced. This decreases compression ratio by an amount that is determined by the timing of the delay of closing of the fuel inlet valves. The inlet valve actuating mechanism increases the delay when engine power output is increased and decreases the delay when power output is reduced and thereby varies compression ratio as needed to provide for more efficient operation throughout the range of power outputs.
The above described mode of operation of prior Miller cycle engines requires the effective size of the combustion chamber to be relatively small. Consequently, a relatively small charge of fuel is compressed to normally high pressure at the time that combustion begins. The following power stroke utilizes the full cylinder volume. This results in a very high expansion ratio during the power stroke enabling the engine to extract more work from a given charge of fuel. This advantage has not heretofore resulted in extensive use of Miller cycle engines in automobiles as the low effective size of the combustion chamber, relative to cylinder volume, causes the prior engines to have a low power output per liter of piston displacement.
The fuel inlet valves and valve operating mechanism of prior Miller cycle engines are not designed to resolve other problems which also adversely affect fuel efficiency. For example, the operator controls the speed and power output of a conventional engine with a throttle valve which is situated in the flow path of the air and fuel. The engine must expend power in order to draw the mixture through the flow path constriction formed by the throttle valve. This throttling toss is a function of the product of the flow rate through the throttle valve and the pressure difference between the upstream and downstream side of the valve. Throttling loss is minimal when the engine operates at maximum power as the pressure difference across the fully open valve is minimal. The throttling loss is also minimal when the engine is operating at or near idling speed as the flow rate through the valve is minimal at that time. Throttle loss rises substantially and may consume as much as 30% of the engine power at the intermediate region of the engines output power range. As has been pointed out above, automobile engines operate within this intermediate power region much of the time. Elimination of the throttle and its attendant losses would substantially increase fuel efficiency of the engine.
The fuel inlet valves of prior engines create significant additional throttling loss. This is particularly pronounced when the inlet valves are spring biased poppet valves such as are present in modern engines. Poppet valves create a very substantial constriction in the fuel and air mixture flow path at the initial stage of opening of the valve and at the final stage of closing of the valve. Opening of the poppet valve is undesirably gradual as it is momentarily stationary at the start of the opening stage. Closing of the valve is also undesirably gradual as it must be brought to a stationary condition during that period. Reduction of this additional throttling loss at the inlet valve would further enhance fuel efficiency of the engine.
Most engines are designed to produce what is known as the squish effect during the final stage of the compression strokes of the pistons. The spark plug extends into a more or less centered recess in the cylinder head surface which forms the top of the combustion chamber. Other portions of the cylinder head surface, termed squish areas, are very closely approached by the power piston as it reaches top dead center position. This speeds the fuel combustion process by driving highly compressed and heated fuel and air mixture towards the spark plug with a rapid and turbulent motion. Hastening the combustion process enhances power output and output and increases fuel efficiency by avoiding fuel detonation. Detonation occurs when an unburned portio
Ali Hyder
Argenbright Tony M.
Zimmerman Harris
LandOfFree
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