The knock sensor is installed in the middle of the engine block. The four-cylinder machine is installed between the 2 and 3 cylinders, or the middle of the 1 and 2 cylinders, and the middle of the 3 and 4 cylinders. Its role is to determine the engine jitter, used to adjust the ignition advance angle when the engine produces knock.
The knocking sensor (KS) signal is used to determine if knocking has occurred and to retard the ignition advance angle during knocking. Detonation sensors are divided into two categories according to their working principles.
(1) Piezoelectric knocking sensor
The piezoelectric (vibrating type) knocking sensor detects the engine knocking using the principle of piezoelectric effect. The sensor is coupled to a voltage amplifier or charge amplifier to amplify the signal voltage and convert the high impedance input to a low impedance output. The piezoelectric KS is a piezoelectric ceramic component composed of a piezoelectric ceramic, a weight and an outer casing.
(2) Inductive deflagration sensor
Inductive deflagration sensor uses the principle of electromagnetic induction to detect engine detonation, which is mainly composed of iron core, permanent magnet, coil and outer casing. When the engine is knocked, the iron core feels vibration, causing the coil flux to change, generating an induced electromotive force. When the inherent vibration frequency of the sensor is the same as the vibration frequency when the engine is knocking, the signal voltage output by the sensor is the largest. The control unit delays the ignition advance angle based on this signal.
Knock sensors are AC signal generators, but they are very different from most other automotive AC signal generators. They detect the speed and position of the shaft as well as magneto-electric crankshaft and camshaft position sensors. They also detect vibration or mechanical pressure. . Unlike stators and magnetoresistors, they are usually piezoelectric devices. They are constructed of special materials that sense mechanical pressure or vibration, such as the ability to generate an AC voltage when the engine is detonated.
Premature ignition, poor exhaust gas recirculation, engine knock caused by low-grade fuel, etc. can cause engine damage. The knock sensor provides a knock signal to the computer (some via the control module PCM), allowing the computer to readjust the ignition timing to prevent further knocking. They are actually the "oxygen sensor" role that acts as the ignition timing feedback control loop.
The knock sensor is placed in different positions on the engine block or cylinder. When vibration or knocking occurs, it produces a small voltage spike that knocks or vibrates. The spike in the peak of the knock sensor is greater. A certain high frequency indicates a knock or knock, and the knock sensor is typically designed to measure frequencies in the 5 to 15 kHz range. When the control unit receives these frequencies, the computer re-corrects the ignition timing to prevent further knocking, and the knock sensor is typically very durable. So the sensor will only be damaged by its own failure.
When the engine knocks, a pressure wave is generated, and the frequency is 1-10KHZ. The pressure wave is transmitted to the cylinder to generate vibration acceleration of the metal point. The accelerometer knock sensor detects the strength of the knocking pressure by measuring the vibration acceleration of the cylinder surface. Premature ignition time is a major cause of knocking. Since the engine is required to emit maximum power, in order not to cause knocking without losing engine power, a knock sensor is installed to allow the electronic control device to automatically adjust the ignition timing.