Combustion detection circuit for a catalytic converter preheater

Details Combustion detection circuit for a catalytic converter preheater Combustion detection circuit for a catalytic converter preheater

1994-08-31

1995-07-11

Chilcot, Jr., Richard E.

Measuring and testing

Vehicle chassis

Steering

324391, G01L 2300

Patent

active

054310440

ABSTRACT:
The present invention is directed to an electrical circuit for detecting the presence of combustion within a catalytic converter preheater. Combustion of an air/fuel mixture within the preheater results in a wide-band high voltage RF signal across a spark plug gap disposed within the preheater, which is trapped by an ignition coil coupled to the spark plug for energizing the spark plug gap. The presence of combustion will effectuate an elimination or absorption of one or more specific frequencies within the RF voltage band. By coupling a combustion detection circuit comprising an inductor-capacitor (L-C) or resistor-inductor-capacitor (R-L-C) network between ground and a low voltage output terminal of a secondary winding of the ignition coil, and properly tuning the network components to one of the specific absorption frequencies, an output voltage of the combustion detection circuit during discharge of the spark plug will be responsive to the absence or presence of combustion in the burner. The output voltage is characterized by (i) a high voltage spike in the absence of combustion during discharge of the spark plug, and (ii) a low voltage spike in the presence of combustion during discharge of the spark plug. A comparator means compares the output voltage with a predetermined threshold voltage and generates a binary high voltage pulse upon the occurrence of a misfire.

REFERENCES:
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SAE Paper 930461, entitled "Spark Plug Voltage Analysis for Monitoring Combustion in an Internal Combustion Engine"; Yuichi Shimasaki et al. (pp. 1-21) (1993).
SAE Paper 930462, entitled "Flame Ion Density Measurement Using Spark Plug Voltage Analysis"; Miyata et al. (pp. 1-11) (1993).

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