Internal-combustion engines – High tension ignition system – Using capacitive storage and discharge for spark energy
Reexamination Certificate
2000-09-25
2002-10-01
Mancene, Gene (Department: 3747)
Internal-combustion engines
High tension ignition system
Using capacitive storage and discharge for spark energy
C335S281000, C336S229000, C336S213000
Reexamination Certificate
active
06457464
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ignition systems for spark-ignited, internal combustion engines which are capable of high pulse repetition rates.
2. Description of the Prior Art
In a spark-ignition internal combustion engine, a flyback transformer is commonly used to generate the high voltage needed to create an arc across the gap of the spark plug and cause an ignition event, i.e. igniting the fuel and air mixture within the engine cylinder. The timing of this ignition spark event is critical for best fuel economy and low exhaust emission of environmentally hazardous gases. A spark event which is too late leads to loss of engine power and efficiency. Correct spark timing is dependent on engine speed and load. Each cylinder of an engine often requires different timing for optimum performance. Different spark timing for each cylinder can be obtained by providing a spark ignition transformer for each spark plug.
To improve engine efficiency and alleviate some of the problems associated with inappropriate ignition spark timing, some engines have been equipped with microprocessor-controlled systems which include sensors for engine speed, intake air temperature and pressure, engine temperature, exhaust gas oxygen content, and sensors to detect “ping” or “knock”.
Advanced, spark ignited, two and four-stroke engines used in the automotive and related industries may employ an ignition and spark plug system capable of multiple firings during each cylinder ignition stroke. Multiple sparking is known as a means for engine diagnostics.
A disproportionately greater amount of exhaust emission of hazardous gases is created during the initial operation of a cold engine and during idle and off-idle operation. Studies have shown that rapid multi-sparking of the spark plug for each ignition event during these two regimes of engine operation may reduce hazardous exhaust emissions. Accordingly, it is desirable to have a fast cycling spark ignition system.
Engine misfiring increases hazardous exhaust emissions. Numerous cold starts without adequate heat in the spark plug insulator in the combustion chamber can lead to misfires, due to deposits of soot on the insulator. The electrically conductive soot reduces the voltage increase available for a spark event. A spark ignition transformer which provides an extremely rapid rise in voltage can minimize the misfires due to soot fouling.
A coil-per-spark plug (CPP) ignition arrangement in which the spark ignition transformer is mounted directly to the spark plug terminal, eliminating a high voltage wire between the conventional engine coil and spark plug, is gaining acceptance as a method for improving the spark ignition timing of internal combustion engines. One example of a CPP ignition arrangement is disclosed in U.S. Pat. No. 4,846,129 to Noble (hereinafter “the Noble patent”). The physical diameter of the spark ignition transformer must fit into the same engine tube in which the spark plug is mounted. To achieve the engine diagnostic goals envisioned in the Noble patent, the patentee discloses an indirect method utilizing a ferrite core. Ideally the magnetic performance of the spark ignition transformer is sufficient throughout the engine operation to sense the sparking condition in the combustion chamber.
To achieve the spark ignition performance needed for successful operation of the ignition and engine diagnostic system disclosed by Noble and, at the same time, reduce the incidence of engine misfire due to spark plug soot fouling, the spark ignition transformer's core material: (i) must have moderately high magnetic permeability; and (ii) must have low magnetic losses. In order to achieve critical performance requirements such as very fast rise times and rapid energy transfer, the magnetic core material must be capable of high frequency response with low loss. The combination of these required properties and performance criteria narrows the availability of suitable core materials. Possible candidates for the core material include silicon steel, ferrite, and iron-based amorphous metal. Conventional silicon steel routinely used in utility transformer cores is inexpensive, but its magnetic losses are too high. Thinner gauge silicon steel with lower magnetic losses is too costly. Ferrites are inexpensive, but their saturation inductions are normally less than 0.5 Tesla (T) and their Curie temperatures (at which the core's magnetic induction becomes close to zero) are typically close to 200° C. This temperature is too low considering that the spark ignition transformer's upper operating temperature is typically about 180° C. Iron-based amorphous metal has low magnetic loss and high saturation induction exceeding 1.5 T, however it shows relatively high permeability, limiting its energy storage capability. An iron-based amorphous metal capable of achieving a level of magnetic permeability suitable for a spark ignition transformer is needed. Using this material, it is possible to construct a toroidal coil which meets required output specifications and physical dimension criteria. The dimensional requirements of the spark plug well region limit the type of configurations that can be used. Typical dimensional requirements for plug-mounted, insulated coil assemblies are less than 25 mm in diameter and less than 150 mm in length. These coil assemblies must also attach to the spark plug on both the high voltage terminal and outer ground connection and provide sufficient insulation to prevent arc-over from the coil to other engine components. The outer ground connection can be made via a return from the engine block, as in typical coil-per-plug systems. There must also be the ability to make high current connections to the primary coil windings typically located on top of the coil.
SUMMARY OF THE INVENTION
The present invention provides a spark ignition system for an internal combustion engine. The system includes a magnetic core-coil assembly and associated driver electronics and is capable of high pulse rate operation because of its rapid charge time (for example, ~100 microseconds using a 12 volt source), rapid voltage rise (for example, 200-500 nanoseconds), and rapid discharge time (for example, ~150 microseconds). It has low output impedance (30-100 ohms), produces high (>25 kV) open circuit voltages, and delivers high peak current through the spark (0.4-1.5 ampere) and high spark energy, typically 6-12 millijoules per pulse. Operation from a 12 volt battery source is readily accomplished using simple driver electronics at rates ranging from single shot to about 4 kHz, which are considerably greater than the current ignition systems can offer. The core-coil assembly may actually be operated using any voltage >5 volts to supply the driver electronics input voltage. The upper voltage supply limit is dependent on the voltage rating of the components used within the driver electronics, so the present system may be operated with conventional 12 V power or with readily available components at higher supply voltages including the 40-50 Volt system now being contemplated within the automotive industry. The charging time of the core-coil assembly is related to the supply voltage of the driver electronics. The higher the supply voltage, the faster the current will increase through the primary winding of the core-coil. This is due to loss reduction in the components that comprise the driver electronics and the ability to source more current. At lower voltages, the voltage drop across the switching element of the driver electronics (typically an IGBT) will limit the available voltage drop across the core-coil. This has the effect of increasing the charge time until a pre-determined current is flowing through the core-coil primary. This type of electronic system (electronic driver plus core-coil) output delivered through a surface gap plug (typical of avionic spark ignition systems) or a conventional J gap spark plug or derivatives results in a high power ignition source with localized heating capa
Fish Gordon E.
Grimes Donald Allen
Papanestor Paul A.
Rapoport William R.
VanBuskirk Bruce
Castro Arnold
Mancene Gene
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