Combustion condition detector for internal combustion engine

Abstract

To correctly sense combusting conditions of an internal combustion engine, an ion current caused by combustion is detected. A combusting condition detecting apparatus for an internal combustion engine comprises a bias voltage generating circuit for applying a bias voltage to an ignition plug provided in a cylinder of the internal combustion engine; an ion current-to-voltage converting circuit for converting an ion current produced in response to the bias voltage into a voltage corresponding to the ion current; a filter circuit for reducing or removing a pulsatory signal upon reception of the voltage signal outputted from the ion current-to-voltage converting circuit; a sensing period setting circuit for defining a predetermined combusting condition sensing period based upon a filter signal outputted from the filter circuit; and an AC component detecting circuit for detecting an AC (alternating current) component in a specific frequency region during the sensing period from the voltage signal derived from the ion current-to-voltage converting circuit.

Dependencies are inferred from the claim text.