Knocksensorer

Knocksensorer, or knock sensors, are electronic devices used in internal combustion engines to detect engine knock, also known as detonation or pinging. This phenomenon occurs when the air-fuel mixture in a cylinder ignites prematurely or unevenly, causing a sharp pressure rise and a characteristic metallic pinging sound. Uncontrolled engine knock can lead to severe engine damage.

A knock sensor is typically a piezoelectric transducer. When the engine knocks, the vibrations caused by the rapid pressure wave generate a voltage signal from the piezoelectric material. This electrical signal is then sent to the engine control unit (ECU). The ECU analyzes the frequency and amplitude of the signal to determine if knock is occurring and its severity.

Upon detecting knock, the ECU can take corrective action to prevent further damage. The most common response is to retard the ignition timing, meaning the spark plug fires later in the combustion cycle. This reduces the pressure inside the cylinder during combustion, thus suppressing the knock. The ECU may also adjust fuel injection timing or mixture in some cases.

Modern vehicles often employ multiple knock sensors, with at least one for each bank of cylinders or even one per cylinder, to accurately pinpoint the source of the knock. The data from knock sensors is crucial for optimizing engine performance, fuel efficiency, and emissions, while simultaneously protecting the engine from potentially damaging conditions.