1. Field of the Invention
This invention relates to detecting faults in an ignition system for an internal combustion engine.
2. Prior Art
When operating an internal combustion engine having an ignition system for providing ignition current to spark plugs located in the cylinders of the internal combustion engine, it is known to sense missing sparks to provide an indication of a fault. Systems for detecting the timing of a spark are also known. These systems are usually offboard the vehicle in a service area and have been typically used in connection with distributor ignition systems.
Distributorless ignition systems (DIS) are advantageous in that they eliminate the distributor with its attendant mechanical wear and thus offer the potential for eliminating the failures due to such mechanical wear. Such systems are known and described in, for example, in "Ignition and Timing Systems", by K. L. Longstaff, Institution of Electrical Engineers Publication No. 181 (1979) entitled Automotive Electronics and in a Society of Automotive Engineers Technical Paper 780327 entitled "A Distributorless Ignition System--Solid State Ignition High Voltage Distribution with Low RFI Emissions" by J. R. Asik, D. F. Moyer, and W. G. Rado, 1978.
The first article referenced above is devoted to review of various types of ignition systems, including DIS. The description of a DIS design for four cylinder application typically includes two ignition coils, each having a single primary winding and a floating secondary winding. Each high voltage terminal is connected to a single spark plug and each ignition coil primary is alternately energized and quickly de-energized, producing opposite polarity ignition voltages at each coil terminal. As a result, pairs of spark plugs are alternately fired, with each firing pair occurring in a compression or exhaust stroke and thereby providing the proper ignition to the engine.
The second article is devoted to a specific type of DIS utilizing a single ignition coil having two primary windings, a floating secondary winding, and four high voltage diodes to steer the ignition voltages to the proper spark plugs. Each high voltage terminal is connected to two spark plugs through a pair of high voltage diodes arranged in opposite polarity. This alternate DIS is suitable for igniting a four cylinder engine. For both types of DIS described, two-state signals are required for each electronic module. Such signals can be generated by an electronic engine control system.
It would be desirable to have a simple, reliable system onboard the vehicle that can detect and store various spark failures for distributorless ignition systems. These are some of the advantages this invention provides.