Introduction to knock sensors

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The knock sensor is a key component in the engine management system of modern cars. It is mainly used to detect knock phenomena inside the engine and transmit relevant information to the engine control unit (ECU) to adjust the engine's operating parameters. The following is a detailed introduction to the knock sensor:
 

1. Definition of knock sensor

The knock sensor is a vibration sensor, usually installed on the engine cylinder block, used to detect knock phenomena inside the engine. Knock refers to the phenomenon that gasoline spontaneously ignites after the spark plug ignites due to excessive combustion speed or excessive pressure and temperature inside the combustion chamber during the combustion process. This phenomenon will produce a high-frequency pressure wave that will cause damage to the engine.
 

2. Types of knock sensors

Common knock sensors are mainly of the following types:

Piezoelectric knock sensor: This sensor uses the characteristics of piezoelectric materials to generate electrical signals when subjected to vibration or pressure changes. Piezoelectric knock sensors have fast response speed and high sensitivity, and are currently the most widely used type.

Magnetostrictive knock sensor: This sensor uses the characteristics of magnetostrictive materials. When subjected to vibration or pressure changes, the magnetism of the material changes, thereby generating an electrical signal. Magnetostrictive knock sensors have high stability and reliability.

Photoelectric knock sensor: This sensor uses the propagation characteristics of light to detect changes in the propagation speed of light to sense the knock phenomenon. The response speed and sensitivity of the photoelectric knock sensor are very high, but the cost is relatively high.
 

3. Working principle of knock sensor

The working principle of the knock sensor is mainly based on vibration sensing technology. When knock occurs inside the engine, the cylinder will generate high-frequency vibrations, which will be captured by the knock sensor. The sensor converts these vibrations into electrical signals and transmits them to the ECU. The ECU determines the degree of knock based on these signals and adjusts the ignition timing accordingly, usually delaying the ignition to reduce or eliminate the knock phenomenon.
 

4. Functions of knock sensor

The main functions of the knock sensor include:

Detecting knock: Real-time monitoring of the vibration inside the engine and capturing the high-frequency pressure waves generated by the knock.

Adjust ignition timing: The detected knock signals are transmitted to the ECU, and the ECU adjusts the ignition timing based on these signals to reduce or eliminate knock.

Optimize engine performance: Help the engine run in the best condition by real-time monitoring and adjusting the ignition timing, improving fuel economy and engine performance.
 

Reduce emissions: Help reduce harmful emissions from the engine by optimizing the combustion process.