INVENTORS: Richard T. ROSS and Charles D. SMULLEN

TECHNICAL FIELD

This invention relates to internal combustion engines. In particular this invention relates to improved two-stroke internal combustion engines having a high power to weight ratio.

BACKGROUND ART

Cuyuna™ developed a conventional 52 lb lightweight two- stroke piston ported engine in the 1970' s, primarily for use with ultralight aircraft. The conventional Cuyuna engine had a single carburetor and a capacitor discharge ignition ("CDI"). The CDI limited the timing of the conventional Cuyuna engine to 18 degrees no matter what the RPM rate. The engine displacement was 429cc. It had a stock muffler and cast aluminum pistons. It had a manual starter. The engine had a flywheel induced ignition. The heads were spherical and the compression readings did not exceed 100 PSI. The conventional engine produced 28HP.

There are many applications today that require a lightweight, high power to weight ration engine. Ultralight aircraft, both manned and unmanned require such an engine. In addition, in the global war on terrorism, unmanned aerial vehicles ("UAV") are used for surveillance and offensive purposes more and more often. The UAVs have a limited payload capacity and need a lightweight, high power to weight ratio engine. For stealth, it is also important that the engine be as quiet as possible.

It may be possible to modify a conventional lightweight two-stroke engine by adding a turbo charger to increase the air pressure through the carburetor. However, with the engine configured with a carburetor, it is difficult to regulate the flow of fuel through the carburetor. The amount of fuel that can be delivered cannot keep up with the amount of air causing the engine to run lean or rich thus reducing the volumetric efficiency rating.

Other approaches to increase fuel intake and horsepower to a lightweight two- stroke engine have been to electronically control either low-pressure or high-pressure fuel injectors. High-pressure injectors are normally located directly in the cylinder head. Gasoline is injected at a pressure that is higher than the combustion pressure. Low-pressure injectors are located at or near the throttle body. If the engine has more than one cylinder they are normally located in the intake manifold. Both of these methods require the addition of a separate oil pump to deliver lubrication to the vital engine parts.

Attempts have been made to attach a single throttle body to an intake manifold to direct air to the intake ports of both cylinders. Unfortunately, the throttle response with such a configuration is not efficient. The velocity of the air flowing through the throttle body, being split into two directions decreases considerably.

What is needed is an improvement to the conventional lightweight two-stroke piston ported engine to increase its horsepower significantly and reduce its output noise level.

What is also needed is a muffler system that can be adapted to many different two- stroke engines and that provides for the scavenging of unburnt fuel and the attenuation of noise.

DISCLOSURE OF INVENTION

The invention improves the performance of a conventional two-stroke engine without adding weight first by adding a variable venturi exhaust system. Testing shows that the improved exhaust system increases horsepower from 28HP to 35HP.

The conventional engine is also made more efficient first by balancing the entire rotating assembly. The bearing journals are line bored to orient the centerline of the crankshaft to be parallel to the top of the crankcase. The balancing and realignment reduce the amount of vibration and resistance within the rotating assembly. This also maintains a consistent rod angle.

The piston sleeve is then bored to increase the bore size to increase displacement of the engine to 433CC.

The pistons are then changed from a cast aluminum piston to an oversized forged aluminum piston. This both reduces the weight of the piston and increases the durability of the piston dome under high operating temperatures. It also decreases the piston-to-piston wall clearance from .009 to .0035. The reduced wall clearance provides for a consistent compression in the cylinder head. The reduced wall clearance also reduces compression loss in the compression chamber because of the tighter clearances between the piston and the piston wall. Also, by using forged pistons, chromium molybdenum piston rings can be used. The combination of these elements produces less vibration, less friction, less noise and more durability.

The head design is changed from a spherical head to what is known as a squash quenched head. The change in head design increases the combustion pressure and directs the flow of burnt gases toward the exhaust port.

The improvements increase the horsepower produced by the conventional engine to 41.92 horsepower.

An electronic control unit ("ECU") is added to the conventional lightweight two- stroke piston ported engine to overcome the problems with the use of a turbocharger to add air and fuel, in a controlled manner, to the combustion chamber with fuel. The ECU typically includes all components in a single component package.

Both fuel and oil pre-mixed together (fuel/oil mix) are injected directly into the crankcase of the engine instead of the conventional approach of using a high- pressure injector at the cylinder head or a low-pressure injector at or near the throttle body. This design approach offers several advantages. First, this sprays the rotating vital parts of the engine with a fuel oil mix to lubricate these parts adequately. Second, the strategically located atomized spray emitted from the injectors adds the benefit of cooling the underside of the piston, which lowers the cylinder head temperature ("CHT"). The reduced cylinder head temperature allows for an increase in the ignition timing at different RPM's. The injector is sized to allow for the proper atomization of a fuel/oil mix as opposed to a fuel only injection.

By injecting the fuel/oil mix directly into the crankcase, the need for a separate oil pump to lubricate the vital moving parts of the engine is eliminated. The intake port is also opened to induct only air through the port. A throttle body controls the amount of air inducted through the intake port.

To improve volumetric efficiency of the delivery of air, a throttle body is provided, one for each intake port. The use of two throttle bodies increases the total volume and velocity of air delivered to each cylinder head.

The volume and velocity of air flowing through the engine is enhanced by the design of an inverted cone muffler system. The muffler system acts as a vacuum, sucking the air inducted through the intake port through the crankcase, transfer ports and cylinder head into the exhaust. The muffler system has a pulsar that pulses at the rate of the rotation of the crankshaft. The back of the chamber redirects the flow of gases back towards the exhaust port. The next rotation of the crankshaft changes the direction of the pulsar. As the overall length of the pulsar, inside of the muffler increases, it decreases the internal volume of chamber "B". As the overall length of the pulsar decreases, it increases the volume of chamber "B". This results in a dampen effect of the harmonics due to the change in direction of sound waves.

Because the muffler system reduces the output sound so effectively, it can be used on lightweight engines that are used for many different purposes. For example, engines used on weed whacker type devices and on lawn blowers typically are excessively loud. Some local communities have noise ordinances that are violated by the loud volume of some engines. The inventive muffler system helps to solve the noise problem and can even avoid noise ordinance violations.

The fuel, spark and exhaust system are all controlled by the ECU.

A unique aspect of the ECU unit with regard to the improved lightweight two- stroke engine is that it controls the fuel/oil mix that is delivered into the crankcase. Injecting fuel/oil directly into the crankcase of a two-stroke engine is unique to this invention. Also, controlling the injection of fuel/oil directly into the crankcase of a two-stroke engine with an ECU is also unique to this invention.

The ECU also controls other critical functions of the engine through a series of sensors. These sensors read the cylinder head temperature ("CHT"), the exhaust gas temperature ("EGT"), the ignition timing, oxygen levels ("02") in the muffler, throttle position, and mass air pressure ("MAP"). The ECU is programmed to control the fuel/oil mix pulse rate through the injectors, into the crankcase based on the reading it gets from the sensors.

The critical levels include the control of the CHT such that it will not exceed approximately 375 degrees F. The initial ignition timing is normally set to 18 degrees at 2000 RPM's increasing variably to approximately 30 degrees at approximately 8000 RPM's. The fuel/oil mix pulse rate at idle (2000 RPM's) is set at approximately 15% of approximately 20 pounds of fuel per hour. The ECU also measures the 02 levels. 02 is the amount of un-burnt oxygen remaining exhaust gases after the combustion cycle. The levels can range from approximately 12 to 16 part per million as compared to parts of gasoline. This communicates how lean or rich the fuel/oil/air mix is at any particular RPM. MAP readings tell the ECU how much vacuum or air pressure on the intake side of the engine. At idle the airflow into the intake port that is controlled by the position of the throttle bodies (more open/more closed) is slow relative to the flow and pressure of the intake air at higher RPM's. As the throttle bodies open to allow more air at a higher rate of speed the ECU measures that pressure and it adjusts the ignition timing and the fuel injector pulse rate.

The previous known design of the throttle body was a single Polaris 38mm throttle body attached in an intake manifold. Through research and development the inventors determined that using dual throttle bodies with a 32mm bore with ECU sensors attached increased the throttle response and total potential RPM's of the engine.

The ECU collects data from all of the sensors and delivers the fuel (pulse rate) such that the Volumetric Efficiency Rate (VER) is between approximately 92-95% at any RPM rate.

The improved lightweight two-stroke engine is a non-reed valve, non-rotary valve piston-ported engine. The invention provides advancements to a piston-ported engine. The resulting inventive engine creates more horsepower than the weight of the engine. In other words, the horsepower to weight ratio exceeds 1: 1. A description of the engine and its various components are set forth below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional side view of an improved high power to weight two- stroke piston ported engine including an inverted cone muffler system.

FIG. 2. is a sectional front view of an improved high power to weight two- stroke piston ported engine.

FIG. 3 is a sectional side view of an inverted cone muffler system from FIG. 1.

FIG. 3A is an enlarged view of the inverted cone portion of the muffler system from FIG. 3.

FIG. 4 is a front view of an improved high power to weight two-stroke piston ported engine with a single combustion chamber head attached.

FIG. 5 is a perspective view of an improved high power to weight two-stroke piston ported engine showing the connecting rods and counterweights. FIG. 6 is a front view of an improved high power to weight two-stroke piston ported engine showing the air intake ports, fuel/oil injector ports, crank shaft and alternator connecting hub.

FIG. 7 is a front view of an improved high power to weight two-stroke piston ported engine showing the start of the transfer ports and the fuel/oil injector ports.

FIG. 8 is a set of graphs generated by a dynamometer showing base line horsepower, torque and fuel flow of an unimproved conventional lightweight two- stroke piston ported engine.

FIG. 9 is a set of graphs generated by a dynamometer showing torque and horsepower generated by the inventive improved high power to weight two stroke piston ported engine.

FIG. 10 is a table and test data showing rpm, torque, horsepower and volumetric flow rate for the inventive improved high power to weight two stroke piston ported engine.

BEST MODE FOR CARRYING OUT THE INVENTION

In order to understand the particulars of the improved lightweight two- stroke engine, it is described in three categories: 1.) Induction; 2.) Exhaust; and 3.) Engine Management.

1. Induction System.

In nearly all piston ported, two cycle engines, the fuel is aspirated by either a single or double carburetor or by direct injection into the combustion chamber. This poses two problems that are overcome in the design of the improved lightweight two- stroke piston ported engine. The first problem relates to aspirating the fuel with carburetors. If carburetors are used, the fuel/oil mixture must flow through an intake port. Gasoline and oil are mixed with air. However, the amount fuel/oil mixed with air that can be delivered to the transfer ports is limited.

The second problem relates to directly injecting the fuel into the combustion chamber. This requires a high-pressure pump. Injecting the fuel directly into the combustion chamber also necessitates the addition of a separate pump that is needed in order to supply oil to the crankcase. This oil is needed to lubricate the crankcase and pistons. Refer now to FIGS. 1-2. The improved lightweight two-stroke piston ported engine overcomes these two problems by directly injecting a 50: 1 fuel/oil mixture directly into the crankcase 48. This innovative design resolves the problems described above. By injecting the fuel/oil mixture (shown for example at 50) directly into the crankcase 48 with fuel/oil injectors 44, the air intake port 42 that is normally used to deliver a fuel/oil/air mixture 22 can now be used exclusively for the delivery of air into the combustion chamber 24. More air flows through the air intake port 42 at a faster rate. The incoming air flow is identified in FIGS. 1 and 2 at 60.

The location of the fuel/oil injectors 44 relative to the crankshaft 46 is important. The fuel/oil injectors 44 are closer to the moving parts that require lubrication (crankshaft 46 and crankshaft bearings (not shown)). The typical flow of the fuel/oil mixture is shown at arrow 50. Additionally, the air pattern that is created by the spinning crankshaft 46 also allows the fuel/oil/air mixture to cool the underside of the piston 32. This results in a low cylinder head 43 temperature and an increase in the available horsepower of the engine. The movement of the piston 32 also applies force on the fuel/oil/air mixture 22 in the crankcase 48 pushing up through the transfer ports 26 (See FIGS. 1-2 and 7) to the combustion chamber 24 at which point it is compressed and ignited.

Direct injection of the fuel/oil mixture 22 eliminates the need for rotary valves or reed valves, which are required on piston ported engines where the fuel is injected directly into the combustion chamber.

Also note that the improved engine can be further improved by the use of counterweights 54, as shown in FIG. 5. 2. Exhaust System.

Refer now to FIGS. 1, 3 and 3 A. The muffler system in the improved lightweight two-stroke piston ported engine is an important component of the engine and it contributes to its ability to increase horsepower over a conventional piston ported engine. As previously stated, directly injecting the fuel/oil mixture into the crankcase 48 and using the air intake port 42 for delivering air to the combustion chamber 24, increases the flow of air to the combustion chamber 24. The muffler system adds to the flow of the fuel/oil/air mixture to the combustion chamber 24. The muffler system includes an inverted cone formed in chamber B by tapered wall 6 that reflects the exhaust pulses and also scavenges the exhaust port 28 for increased horsepower. The inverted cone system is improved by adding a pulsar P forward of the cone. The pulsar P is formed with a length of pulsar pipe 8, which extends into chamber B of the muffler. A flange 8A is positioned on the leading edge of the pulsar pipe 8. The pulsar P improves the inverted cone system by varying the direction of the exhaust gases in the main chamber A. As the piston 32 is coming up, the exhaust gases are exiting through the exhaust port 28 along with some of the un-burnt fuel. The pressure of the exhaust gases presses against the flange 8A and the pulsar pipe 8. Movement of flange 8A and pulsar pipe 8 is resisted by spring 12. As the exhaust pressure moves flange 8A and pulsar pipe 8 to compress the spring 12, kinetic energy is built up in the spring 12. The kinetic energy in the spring 12 is released thereby pushing the pulsar pipe 8 and the flange 8A toward the exhaust port, and therefore pushing unburnt fuel back to the combustion chamber 24. This results in an increase in low-end torque and a reduction of exhaust noise to near zero.

The surface area of the flange 8 A and the spring constant of spring 12 of the pulsar P can be varied to obtain the desired pulse return rate.

The inventors have observed that the rate at which the air flows though the air intake port 42, without the combination of the fuel/oil mixture (which is injected into the crankcase 48) compliments the pulsar P, allowing the engine to operate more efficiently.

The inventive muffler is used to attenuate sound from an internal combustion engine and is not limited to its use on the instant improved lightweight two-stroke piston ported engine. The muffler is designed and constructed to dissipate the potential energy of exhaust gases using a variable outlet. This is accomplished when the exhaust gases exit through the initial exhaust housing into the chamber B typically having a diameter of approximately 3 1/2 inches that houses and forms the venturi.

Pressure will build within the chamber B and some gases will exit through the venturi port 2 creating a negative pressure in the tapered region 4 around the venturi. As gases hit the tapered wall 6 surrounding the venturi port, backpressure is created changing the direction of the gases. The backpressure also modulates the length of the venturi. The tapered portion of the initial exhaust housing/chamber defined by the tapered wall 6 is typically approximately 7 inches where it joins the exhaust pipe. The pulsar pipe 8 extends onto tailpipe 10. The pulsar pipe 8 may also fit inside of tailpipe 10.

Overall, the length of pulsar pipe 8 and the tailpipe 10 extend approximately 7 inches into the taper of the chamber B. A flange 8 A with a central hole 2 is mounted on the end of the exhaust pipe, and a compression spring 12 is positioned on the outside of tailpipe 10 and pulsar pipe 8 (See FIG. 3A). The pulsar pipe 8 is slidably mounted outside the tailpipe 10. The pulsating back flow gases induce an axial vibration of the pulsar pipe 8 in the tailpipe 10. The pulsations of pulsar P both reflect unburnt gasses back to the exhaust port 28 and attenuate noise. The silencer 18 is positioned at a downstream distance from the venturi, and includes a chamber C having fiberglass packing 14 for further reducing output noise levels. A conventional perforated tube 16 is inside of the fiberglass packing 14 which allows sound pressure to attenuate into the fiberglass packing 14. It is notable that the venturi chamber 4 formed between the tapered wall 6 and tailpipe 10, reduces the output noise from the muffler considerably; even without the output noise reduction provided by the silencer 18 and fiberglass packing 14.

It is to be understood that the dimensions provided herein are to be considered as representative and they may vary depending upon the volume or displacement and the RPM of the motor. The configuration of the muffler system is consistent, but the size, dimensions and volume may change, depending upon the size and RPM of the motor.

3. Engine Management System.

The engine is managed by an Electronic Control Unit ("ECU"). The ECU is an electronic control unit that controls the function of the engine in real time. In other words, when the engine is revved up the ECU controls the timing of the firing of the spark plug and the amount of fuel that is delivered to the engine. This compensates for high cylinder head 43 temperatures and any load changes that the engine encounters.

Custom throttle bodies have been added to the intake ports. The throttle bodies are matched to the intake port and are sized to compliment the flow of air to the combustion chamber and exhaust system.

4. Test Results.

FIG. 8 is a set of graphs produced by a dynamometer from a conventional lightweight two-stroke piston ported engine. The maximum horsepower produced by the conventional engine was 30 HP. FIG. 9 shows a set of graphs produced by a dynamometer that shows the torque and horsepower produced by the improved lightweight two-stroke piston ported engine after a modified fuel/air carburetor was fitted to the air intake port 42 (See FIGS. 1-2 and 4) . The improved engine produced 40.9 horsepower. FIG. 10 shows a table from a dynamometer that includes RPM versus torque and horsepower values after only air was injected into air intake ports 42 and fuel/oil was injected into fuel/oil injector ports 44 (See FIGS. 1-2 and 7). The dynamometer results from FIG. 10 indicate the improved engine produced a peak power of 48.4 horsepower. It is important to note that the 48.4 HP rating is not the maximum horsepower that the improved lightweight two-stroke piston ported engine can create. The power band of a two-stroke engine is tunable depending on the component parts of the engine. Adjustments can be made to the throttle bodies and/or to the exhaust system to vary the operating power curve. The power can be increases at higher or lower RPM's by modifying the throttle bodies. The 48.4 HP produced in FIG. 10 is based on the throttle bodies and exhaust pipes that were used at the time of the dynamometer run. If these components changed the amount of HP created at various RPM's would change. For example, if peak power is needed at lower RPM, the bore of the throttle bodies would be increased and the length and taper of the inverted cone 6 of the muffler system would be decreased. Also, the crankcase 48 can be polished to improve the delivery of the fuel/oil mixture to the combustion chamber 24.

This allows the improved lightweight two-stroke piston ported engine to be tuned to adjust the HP as required for a variety of applications. If 55 HP was required, for example, the throttles and exhaust pipes could be modified to create additional horsepower. If the horsepower need to be higher at a lower RPM rate this can also be accomplished by adjusting the throttle bodies and exhaust pipes.

It is important to note that in order for the improved lightweight two- stroke piston ported engine to function most efficiently and create additional horsepower over a conventional piston ported engine, all of the above mentioned improvements should work in conjunction with each other. The fuel/oil mixture must be injected directly into the crankcase. The exhaust system with its unique pulsar must be attached to the engine. The ECU must be programmed properly to the size of the engine. And the throttle bodies must be sized properly to control the airflow through the intake ports. If any of these parts are not assembled properly the engine will not function in its most efficient manner.