Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Reexamination Certificate
1995-06-07
2001-04-10
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
C239S005000
Reexamination Certificate
active
06213089
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
A new electro-thermal pulsed energy fuel injection system for fuel flow rate control through pressure pulse width.
BACKGROUND—DESCRIPTION OF PRIOR ART
With improvement in internal combustion engines, the air/fuel distribution adds the requirements of timing and air quality control. Fuel injection to piston engines is one of the means to achieve the goal. Known fuel injection systems use a mechanical pump to produce high pressure, then either mechanical or electromagnetic means are used to control the timing of the fuel injection. In the case of the diesel engine, it is even more complex due to the high pressure required to inject the fuel into the cylinder.
Diesel engines are more efficient, in general, than gasoline engines because of their inherent high pressure ratio and because they can operate at very lean fuel-air ratios. Diesel invented the cycle to mimic closely the Carnot Cycle, and the centerpiece of his difficulty was the “programmed coal powder injection” to give him the constant pressure combustion. Cummins invented the liquid fuel injector to put the diesel engine on the commercial market and founded the Cummins Engine Company, but he did it with the sacrifice of the idea of constant pressure combustion. Diesel engines can improve efficiency by implementing a controlled fuel injection system. The current mechanical fuel injection system using a high pressure fuel pump normally creates a high-burst pressure for the combustion of the injected fuel. It is not uncommon to have fuel pressure which exceeds 3000 psi before injection. The reason for having the high pressure is twofold. First, a diesel cycle operating in “self-ignition mode” has to be a high pressure ratio machine, and higher pressure is necessary before fuel can be injected into the engine. Second, the injector is also an atomizer, which injects the fuel in the form of fine droplets, which also requires pressure.
It is the second element which influences the ability of the engine to operate at a higher RPM. The atomization process is a method of suddenly increasing the surface area of a given volume. The work done is against the surface tension. The energy to do the work is stored in the form of compression energy, which is partially compression of the diesel fuel and partially the spring property of the fuel line. The fuel line from the diesel pump to the fuel injector is usually highly tuned.
Another difficulty of the injection system is that its mechanical linking to the engine makes it difficult to advance timing when the RPM is changed. This is the major reason that gasoline engines equipped with a spark ignition timing system allow convenient increase of the RPM. The advance in timing is to compensate the ignition delay of the fuel combustion. This may be one of the major bottlenecks of diesel engines. As in the gasoline engine, the tuning of the engine is mostly an advanced time mechanism.
Many attempts have been made to improve diesel fuel injection systems, especially in the area of piezoelectric fuel injector systems. The piezoelectric system utilizes an electrical pulse put across the surface of a piezoelectric crystal. The result is to change the dimension of the crystal in the direction of applied voltage. The deformation of the crystal is very small; therefore, usually a large stack of piezoelectric crystals are required in order to provide enough displacement to be useful. The piezoelectric crystal does not change its volume, so when the compression of the piezoelectric crystal is done by the applied voltage, the dimension expands perpendicular to the applied voltage direction of the crystal. The net result is that the volume of the crystal remains approximately a constant. A piezoelectric crystal cannot therefore be used as a pump effectively. The application to date has been to use the piezoelectric stack to relieve the fuel pressure from the injection line as an electrically controlled cut-off system; therefore, the fuel pump can be made much more easily without a spiral timing device and also does not have to rotate through a rack and pinion system for the time duration control. Unfortunately, such a system is very expensive and has only been tried experimentally on large diesels. The RPM issue cannot be addressed, because the beginning of the timing of injection of the fuel is still controlled mechanically by a high pressure fuel pump. Other electrical mechanical devices have been tried, but none can produce the rapid pressure rise required to inject the controlled amount of fuel. The duration of the injection at 6000 RPM is about a millisecond or less, and the amount of fuel injected is on the order of milligrams for most small engines.
OBJECTS AND ADVANTAGES
The objective of the invention is to remove or reduce the pressure raise of mechanical fuel pumps for pulsed fuel injection systems. A new concept by rapidly pulsing thermal energy to convert fuel from liquid phase to vapor phase then collapse the vapor volume when heat input is removed as a means to produce sharp pressure drop-off for fuel cut-off is introduced. The system can electrically heat a high temperature wire such as platinum or can use a high voltage system to draw a controlled electrical arc. Since no air is present, no combustion would be induced. This rapid change of thermal energy transfers the heat to the fuel, heating it rapidly to a vapor state. The changing from liquid to vapor state requires a change in volume of several orders of magnitude change in volume. In a small volume chamber, very high pressure is produced. This method essentially removes the need of a very high pressure fuel pump. The electrical pulsing is extremely manageable with today's electronic circuitry. An artificial intelligence program for fuel pulse management would be possible for the monitoring of engine requirements such as output horsepower, RPM, engine conditions such as NOx, smoke and knocking effects via analog to digital converters. This invention simplifies the mechanical system and makes use of computer technology. The advantage of the Applicant's invention is to overcome obstacles in mechanical pump high pressure fuel injection systems. The objective is to make it mechanically simple. For example, other objectives are:
a) to reduce injector size;
b) to reduce the surface tension of fuel by heating;
c) to reduce the droplet mist size;
d) to improve the interface of computer to fuel management; and
e) to reduce pollution and smoke.
Other benefits include the ability to have constant pressure combustion, so a diesel engine can be closer to the cycle Diesel invented, and, in the case of the gasoline engine, direct cylinder fuel injection becomes feasible again.
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Argenbright Tony M.
Cooper & Dunham LLP
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