Patent ID: 6865929

Claim:
A combustion state detection apparatus of an internal combustion engine, comprising: an ignition coil; and a control unit, wherein the ignition coil comprises: an ignition coil primary current switching section; an ion current detection section which detects an ion current output from the ignition coil primary current switching section; a failure determination signal output section which outputs a failure determination signal of an ignition operation of the internal combustion engine; and an ion current detection signal output section which outputs an ion current detection signal, wherein the ion current detection signal includes the ion current detected by the ion current detection section and the failure determination signal output from the failure determination signal output section, wherein the control unit comprises: a combustion state detection section which detects a combustion state of the internal combustion engine based on the ion current detection signal output from the ion current detection signal output section of the ignition coil; and a failure determination section which also receives the ion current detection signal output from the ion current detection signal output section of the ignition coil, and determines failure of the ignition coil based on the ion current detection signal.