1. Field of the Invention
The present invention relates to internal combustion engines in which a compression boost for the fuel-air mixture directed into the intake of the combustion chambers of the cylinders is derived from the backside of the pistons. In particular, the present invention relates to an internal boost system which may be retrofit onto an internal combustion engine or which may be directly incorporated into modern internal combustion engine designs.
2. Background of the Invention
Traditionally, the performance (i.e., horsepower) of internal combustion engines has long been increased by the addition of superchargers or turbochargers. To understand how a supercharger or turbocharger operates, it is helpful to think of an engine as a giant air pump. The engine's four-stroke cycle first allows the pistons to draw air in through the intake manifold and intake valves. The air is then compressed by a piston while all the valves are closed and ignited by the spark plug. The resulting explosion forces the piston down in the power stroke. The final stage of the four-stroke cycle is when the piston comes back up and forces the spent gases out of the exhaust valve.
In theory, a denser air charge (also mixed with fuel) will create a more powerful combustion explosion inside the cylinder, thus creating more downforce on the piston which translates into horsepower. The supercharger or turbochargers act as compressors or air pumps which are capable of increasing the air charge by force feeding air into the combustion chamber thereby creating a denser air/fuel mixture. This mechanically increases the compression ratio by forcing a boosted (pressurized) air/fuel mixture in the combustion chamber. The denser charge increases the dynamic cylinder pressure upon ignition to create more engine power.
Although supercharging and turbocharging technology has evolved into a viable means for producing more horsepower, it does have some drawbacks. Most superchargers are belt driven from the engine itself and can consume up to 20 percent of the engine's total power. On the other hand, since turbochargers are driven from the exhaust of the engine, the turbocharger is exposed to high heat which results in premature wear of the turbocharging system components.
Other less traditional forms for increasing horsepower (i.e. dynamic cylinder pressure) have also evolved such as utilizing the backside of the pistons to compress air in the internal lower cavity of the engine block and routing the compressed air back into the intake system of the engine, thus, increasing the air pressure directed into the combustion chamber similar to that of supercharging or turbocharging.
For example, U.S. Pat. No. 6,763,801 to Decuir [hereinafter “Decuir '801”] teaches an internal combustion engine utilizing internal boost. In particular, Decuir '801 teaches sealing off the internal cavity of an engine by installing a plate 4A, 4B above the oil reservoir creating a plurality of separate internal compression chamber inside the engine. A one-way reed valve 10 is installed into the case of the engine block 2 which allows air to drawn into the internal engine cavity. Additionally, a one-way exit reed valve 11 is installed in the engine block 2 to allow compressed air to be exhausted from the internal engine cavity and to be routed into the engine intake manifold. When the pistons are driven towards the top of the combustion chamber, air from outside the engine is drawn into the internal engine compartment. When the pistons are driven downward, the pressure inside the chamber is increased and air is forced outside the block through the exit reed valve 11. The exiting air is then directed into the intake of the engine to boost the dynamic cylinder pressure upon ignition to create more engine power.
Even though internal boost technology appears to be a viable source of “free” horsepower (i.e. non-parasitic) as compared to supercharging technology, internal boost technology is still relatively in its infancy stage with regard to development. Since the aforementioned Decuir '801 patent was filed, engine technology has steadily been advancing. The Decuir '801 teaching is based upon an air-cooled VOLKWAGEN engine which is a flat horizontally opposed four cylinder engine in which there are two banks of cylinders (two cylinders per bank). This engine configuration dates back to pre-World War II technology developed in Germany. Although, this “VW” engine is famous for its simplicity and reliability, it has since been passed up for more modern water cooled inline four and six cylinder engine configurations and for V-configured engines (e.g., V6, V8, V10, etc.). Furthermore, since the Decuir '801 patent has been filed, the aforementioned engines have also significantly evolved incorporating many modern engine manufacturing and design concepts. For instance, state of the art engine blocks may no longer be heavy one-piece unit casts from iron. Instead, the engine manufacturers have adopted highly refined “modular” engine platforms which utilize light weight cast components such as unitary lower main journal plates (instead of individual journal caps), engine front covers, and cast oil plans (instead of steel stamped or pressed oil pans).
It would be beneficial to incorporate internal boost technology into more modern engine platforms. Moreover, it would be advantageous to provide an internal boost system which is simple to manufacture and of which utilizes few parts. An ideal internal boost system could either be integrated into modern modular engine platforms, or retrofit onto existing traditional cast engines.