Internal-combustion engines – High tension ignition system
Reexamination Certificate
2000-01-19
2001-04-17
Solis, Erick (Department: 3747)
Internal-combustion engines
High tension ignition system
C123S649000, C073S117020
Reexamination Certificate
active
06216678
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to misfire detection and, more particularly, to a method and apparatus for precisely and selectively generating misfires in an engine for use in developing and evaluating misfire detection schemes.
BACKGROUND OF THE INVENTION
Governmental requirements for the onboard diagnostics (OBD) of engine misfires necessitate specialized instrumentation to develop, calibrate, and test misfire detection algorithms. Specifically, equipment designed to induce engine misfires at precisely controlled rates is needed to determine thresholds for emissions and signal detection, and to demonstrate regulatory compliance. This “misfire generator” must interact with the engine's ignition system so as to prevent spark for certain firing events, without affecting the normal firing events before and after each occurrence.
SUMMARY OF THE INVENTION
In accordance with the present invention, a misfire generator is provided that is compatible with most existing ignition systems including those with a distributor, distributorless and coil-on-plug ignitions. When generating misfires, the coil driver's electrical diagnostic is not affected, thereby avoiding possible confusion and unintended interactions between ignition diagnostics and the OBD misfire monitor.
The device of the present invention provides a misfire logic signal for initiating a misfire, and further provides a special version of the misfire logic signal, suitable for recording by a data acquisition system. This latter signal is synchronized to crankshaft position to indicate precisely in the data file which ignition events were induced misfires. The equipment only needs connections to the driven sides of the ignition primaries, as well as power and ground. The misfire generator operates properly with multi-strike ignitions, and overlapping dwell, and is not detected by ignition diagnostics based on either coil primary current or flyback voltage.
The method by which the equipment of the present invention electronically defeats spark is different from prior equipment. Whereas the prior device interrupts primary coil current, the proposed device does not. Rather, it generates misfire by clipping the flyback voltage on the coil primary to far less than the usual several hundred volts when the coil current is interrupted by the coil driver, thus preventing the ignition coil secondary from generating the thousands of volts needed to jump the spark plug gap.
This approach offers several advantages, one of which is that the electronics can generally be connected with only a “T” connection to each coil primary. As a practical matter, this mean that only one jumper connection per coil (rather than two) is required. An exception, discussed below, is when the equipment must be connected with a Y configuration in order to defeat certain types of ignition diagnostics.
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Baker Ryan Lee
James John Victor
Krzyske Dennis Carl
Ford Global Technologies Inc.
Lippa Alan J.
Solis Erick
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