ION SENSOR [SKYACTIV-G 2.0]
Purpose
Detects knocking occurrence condition (pre-ignition) due to high compression ratio.
Detects the combustion condition in the cylinder by detecting the ion current generated during combustion.
Function
Detects the ion current generated during combustion as electric current by applying voltage to the spark plug and amplifying it in the ion current detection circuit integrated in the ignition coil, and sends it to the PCM.
Construction
The ion sensor is built into the ignition coil.
Ion current generation mechanism
Ions are generated inside the cylinder due to a chemical reaction during combustion and thermal ionization caused by the pressure increase inside the cylinder. To detect the ions as electric current, voltage is applied to the center electrode of the spark plug.
Electric current flows by the generated negative ions moving to the center electrode of the spark plug to which voltage is applied and the positive ions moving to the grounded engine wall surface.
Operation
Accumulates the secondary current of the ignition coil in the ion detection circuit (1), and detects ion current (2) by applying the voltage to the spark plug.
Because the detected ion current is a very small current, it is amplified in the ion detection circuit (1) and sent to the PCM (3).
After the spark plug discharges, voltage is applied to the center electrode and ion current generated inside the cylinder from the beginning to the completion of a combustion is detected.
Generation of ion current varies depending on the combustion process. Because it varies similar to the combustion/pressure inside the cylinder, an abnormal condition is determined if ion current is generated except during a normal combustion.
Fail-safe
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Not applicable