Internal-combustion engines – High tension ignition system – Safety device
Patent
1994-06-06
1996-02-13
Nelli, Raymond A.
Internal-combustion engines
High tension ignition system
Safety device
F02P 1100
Patent
active
054904897
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Ignition circuit monitoring for ignition systems is already known in which a sensor signal is generated by an ignition current sensor when each ignition takes place, this sensor signal being stored in a memory and read out after each ignition. The memory content is reset, in turn, after each subsequent ignition, so that an ignition failure is recognized when there is no sensor signal. This ignition circuit monitoring, however, offers no possibility of detecting the frequency of misfirings or the loading of the ignition system due to misfirings. Thus, for example, a single misfiring which is then followed by a very large number of proper ignitions is negligible, but it is disadvantageous when the number of misfirings equals the number of proper ignitions.
SUMMARY OF THE INVENTION
In the ignition system according to the present invention an ignition-diagnostic signal is detected and selectively evaluated for each cylinder. After an ignition, the ignition-diagnostic signal is statistically weighted for each cylinder in an evaluation device, so that the threshold for introducing emergency measures to protect the catalyzer is only exceeded at a certain number of ignition failures in a specified time. A further advantage may be seen in the fact that the ignition in the cylinder does not have to be interrupted so that this cylinder is able to be corrected.
In accordance with an embodiment of the present invention, an amount which is larger than 1 is added to the previous diagnostic value, in the case of a faulty ignition, and the value 1 is subtracted in the case of a correct ignition in order to form the weighted ignition-diagnostic value. The value, which is to be added in the case of a faulty ignition, is determined in practice for each engine type. The threshold, from which emergency measures are introduced, is also determined in practice. Finally, it should also be mentioned as an advantage that the weighted ignition-diagnostic value (ZUNTAB) is limited to an applicable maximum value (AFXDZU) on reaching the latter, and the number of correct ignitions until correction of a previously defective cylinder has been recognized is fixed by means of the interval between the fault threshold (AFSDZU) and the maximum value (AFXDZU).
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the construction, in principle, of an ignition system for detecting the ignition-diagnostic signal;
FIG. 2 shows an ignition-diagnostic signal;
FIG. 3 shows the sequence of the program for weighting the ignition-diagnostic signal; and
FIG. 4 shows a diagram of the weighted ignition-diagnostic value for one cylinder.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a distributorless ignition device, which consists of a microprocessor 1, ignition coils 2 and 3 (it also being quite possible to connect further ignition coils, as is indicated by interrupted lines) sparking plugs 4 and 5, ignition transistors 6 and 7, an ignition-current sensor 8, a monitoring circuit 9 and an evaluation device 10 arranged in the microprocessor.
The primary windings of the ignition coils 2 and 3 are connected to the battery voltage U.sub.B, so that when the ignition transistors 6 and 7 are triggered by the microprocessor 1, a charging current flows in the corresponding primary winding of the ignition coil 2 or 3. The dwell periods of the ignition transistors are fixed by an ignition computer contained in the microprocessor 1. In order to initiate ignition, the ignition transistor is forced into the blocked condition, so that a high voltage is generated in the secondary windings of the ignition coils, and this high voltage produces an ignition spark at the spark plugs. An ignition current sensor 8 is arranged in the secondary circuit of each ignition coil between the output of the secondary winding and earth in such a way that all the secondary windings are previously connected together at a point 11. In this way, the ignition current sensor 8 detects the signals from all the ignition coils. In order to detect an ignition signal, it
REFERENCES:
patent: 5058551 (1991-10-01), Nakaniwa
patent: 5134987 (1992-08-01), Mayer et al.
Hoeptner Wolfgang
Kaltenbrunn Peter
Mayer Ulrich
Mischker Karsten
Nelli Raymond A.
Robert & Bosch GmbH
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