Car knock sensor function
The main function of the automotive knock sensor is to detect the knock phenomenon of the engine, and prevent the knock by adjusting the ignition advance Angle, so as to protect the engine from damage.
The knock sensor converts the mechanical vibrations of the engine into electrical signals that are transmitted to the electronic control unit (ECU). The ECU adjusts the ignition advance Angle according to the received signal to avoid the continuous occurrence of detonation. The knock sensor usually uses piezoelectric ceramic technology. When the engine shakes, the ceramic is compressed and deformed to produce an electrical signal, which is transmitted to the ECU through a shielded wire for processing.
The working principle of the knock sensor is based on the piezoelectric effect, when the engine knocks, the piezoelectric ceramics inside the sensor are squeezed, generating an electrical signal. These signals are sent to the ECU, which adjusts the ignition advance Angle based on the stored data to prevent knocking. In addition, knock sensors can sense the speed and position of the engine, providing multiple information to help optimize engine performance.
The knock sensor is usually installed in a specific location in the engine block, such as between the 2 and 3 cylinders of a four-cylinder machine or between the 1 and 2 cylinders and a 3 or 4 cylinder. Its mounting position ensures a sensitive capture of tiny engine vibrations and knocks.
If the knock sensor fails, although it will not cause the engine to fail to start, it will cause problems such as engine jitter, power loss, fuel economy deterioration, and fault lights. Therefore, the proper operation of the knock sensor is crucial to the engine performance.
Automotive knock sensor is a device installed on the engine block, mainly used to detect the knock of the engine. There are many types of knock sensors, the most common of which include magnetostrictive and piezoelectric ceramic.
Type and structure of knock sensor
Magnetostrictive : consists of a magnetic core, a permanent magnet and an induction coil. When the engine vibrates, the magnetic core shifts, resulting in a change in magnetic flux in the induction coil, resulting in induced electromotive force .
piezoelectric ceramic : When the engine shakes, the ceramic inside is squeezed to produce an electrical signal. Because the signal is weak, the connection cable is usually wrapped with shielded wire .
piezoelectric resonance : installed on the upper part of the engine body, the use of piezoelectric effect to convert mechanical vibration into electrical signals. When the knock vibration frequency is consistent with the natural frequency of the sensor, resonance phenomenon will occur, and the high knock signal voltage will be output to the ECU, according to which the ECU will adjust the ignition time to avoid knocking .
How a knock sensor works
The knock sensor senses the vibrations and sounds of the engine and converts them into electrical signals that are sent to the engine control unit (ECU). The ECU adjusts the ignition advance Angle according to the received signal to prevent the occurrence of detonation. The specific working principle is as follows:
Magnetostrictive : engine vibration causes the magnetic core to shift, changing the magnetic flux in the induction coil, resulting in induced electromotive force .
piezoelectric ceramic : when the engine shakes, the piezoelectric ceramic is squeezed to produce an electrical signal, the ECU adjusts the ignition time according to the signal.
piezoelectric resonance type : when the knock vibration frequency is consistent with the natural frequency of the sensor, a resonance phenomenon occurs, and the high knock signal voltage is output to the ECU.
The role of knock sensors in cars
The main function of the knock sensor is to measure the jitter degree of the engine. When the engine produces knock, the electric signal is transmitted to the ECU, and the ECU adjusts the ignition advance Angle accordingly to prevent further knock. Knock can cause engine damage, so knock sensors play a vital role in protecting the engine .
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