Patent ID: 6118276
Filing Date: 2000-09-12
Classification: F02P

Abstract:
An ion current detection device comprising:a diode connected in series with a spark plug and an ignition coil secondary winding, the diode passing current only in a direction of a secondary current that flows when an ignition coil primary current is shut off;a capacitor connected in series with said spark plug, said ignition coil secondary winding, and said diode, the capacitor acting as an ion current generating source;a voltage-regulator diode connected in parallel to said capacitor, the voltage-regulator diode limiting a voltage to be charged into said capacitor by said ignition coil secondary current to within a specified value;a series connection of a detecting resistor and a load resistor, connected in parallel with said doide and forming an ion current path together with said capacitor, said ignition coil secondary winding, and said spark plug, wherein a resistance value R.sub.1 of said detecting resistor is less than a resistance value R.sub.2 of said load resistor and wherein the resistance value R.sub.1 of said detecting resistor and the resistance value R.sub.2 of said load resistor are related byV.sub.z .times.{R.sub.1 /(R.sub.1 +R.sub.2)}<V.sub.bwhere V.sub.z is the maximum voltage of said capacitor limited by said voltage-regulator diode, and V.sub.b is the supply voltage of said device; andan inverting circuit connected to a node between said detecting resistor and said load resistor.