Robert Boschgmbh

Adolf Dreyer

Herman Roozenbeek

Ulrich Bentel

Circuit arrangement to detect knocking

A circuit for recognizing missing or poor firings in Otto (gasoline) engines with multi-circuit ignition systems features a voltage tap on the primary side of each ignition coil (10, 11), leading to a respective controllable transistor (16, 19). A common junction point (21) for the respective transistors provides signals, representative of the control states of the transistors, for evaluation (32). These signals correspond to the respective spark burning voltages. The cylinders fire sequentially, so the voltage patterns of the respective cylinders appear sequentially at the common junction point, and it is possible, even in multi-circuit ignition systems, to monitor the individual ignition circuits in a simple manner, and to interrupt fuel supply to any less-than-optimally firing cylinder, thereby preventing unburnt hydrocarbon overload on the catalytic converter and on the environment. Preferably, the evaluation circuit includes an A/D converter (33) and an INTEL 8051 microprocessor (34).

Apparatus for recognizing missing or poor firings in otto engines

To reliably distinguish between knocking signals derived from an internal combustion engine knock sensor from all the other signals likewise derived from the knock sensor, which includes background noise signals, statistically distributed disturbance signals and the like, a correlation signal is generated, and the received signal is correlated with the correlation signal, which is cyclically varying at an average frequency which is of the frequency of the expected knocking signal, or a whole number multiple thereof. An output recognition is provided upon correlation between the correlation signal and the signal from the knocking sensor. The system can be implemented by a signal generator (6, 61, 62; 63) which provides the correlation signal, correlation being effected by an AND-gate (7, 71, 72; 73), or by software in a microprocessor in which an incoming knocking signal is interrogated in cadence with cyclical variation at the frequency which is the expected knocking frequency of the engine.

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Hemmingen, Germany

Adolf Dreyer