Automotive sensor applications and development trends

I. Introduction

Automotive electronic technology is one of the core technologies for the development of the automotive industry. As the information source of automobile electronic control system, automobile sensor is a key component of automobile electronic control system, and also one of the core contents of research in the field of automobile electronic technology. The number and technical level of automobile sensors determine the performance of automobile control system. Generally, there are dozens to nearly 100 sensors installed on an ordinary household car, and the number of sensors in a luxury car can reach more than 200, which are mainly distributed in the engine control system, chassis control system, body control system and navigation system.

Second, the characteristics of automotive sensors

Automotive sensor technology is a technology developed with the development of automotive electronics. The car sensor is the input device of the car's electronic control system. It converts various operating conditions such as vehicle speed and engine operating conditions during the operation of the car into electrical signals and sends them to the central control unit to keep the engine in the best working state. Automobile sensors can perform real-time, effective and accurate measurement and control of temperature, pressure, position, speed, acceleration, flow, humidity, electromagnetic, photoelectric, gas, vibration and other information. Because the temperature and climatic conditions in the driving environment of the car are very different, the sensor is required to have a strong adaptability and can work normally in the environment of -40 ℃ to 100 ℃: at the same time, the car sensor must also withstand various Disturbance and vibration caused by road conditions during driving. Therefore, the automotive industry has extremely strict requirements on sensors. Automotive sensors must have the characteristics of high stability and precision, fast response, good reliability, strong anti-interference and anti-seismic capabilities, and long service life.

3. Application of automotive sensors

l. Engine control system sensor

The engine control system sensor provides various information to the engine's electronic control unit. The electronic control unit processes the information and sends precise control commands to the engine to control the engine so that the engine can work normally under various operating conditions. The use of such sensors can improve steam

The car's power performance and comfort, reduce fuel consumption, reduce exhaust emissions, and correctly reflect driving failures.

(1) Temperature sensor

Mainly detect engine temperature, suction gas temperature, cooling water temperature, fuel temperature, engine oil temperature, catalytic temperature, etc. The practical temperature sensors are mainly wire wound resistance type, thermistor type and thermocouple type. Winding resistance temperature sensor has high accuracy, but poor response characteristics; thermistor sensor has high sensitivity and good response characteristics, but poor linearity, and low applicable temperature; thermocouple type has high accuracy and wide measurement range, but amplifier must be considered And cold-end processing problems.

(2) Pressure sensor

There are pressure sensors that detect the pressure of the brake hydraulic system and the lubricating oil system, and the manifold pressure, wind pressure, atmospheric pressure and tire pressure sensors that measure the pressure of the gas medium. At present, the most commonly used pressure sensors for vehicles are capacitive, piezoresistive, differential transformer (IVDT) and surface elastic wave (SAW).

Capacitive sensors have the characteristics of high input energy, good dynamic response, and good environmental adaptability; the varistor type is greatly affected by temperature, and a separate temperature compensation circuit is required. However, it is suitable for mass production; the LVDT type has a large output and is easy to digital output, but the interference resistance is poor: the SAW type has small size, light weight, low power consumption, high reliability, high sensitivity, high resolution, digital output, etc. Features. Used for pressure detection of automobile intake valve. It can work stably at high temperature and is an ideal sensor.

(3) Speed, angle and vehicle speed sensors

Mainly used to detect crankshaft angle, engine speed, vehicle speed, etc. There are mainly electromagnetic type, magnetic resistance type, Hall effect type, optical type, vibration type and so on.

(4) Gas concentration sensor

It is mainly used to detect gas and exhaust emissions in the car body, the most important of which is the oxygen sensor. The oxygen sensor is installed in the air pipe to measure the oxygen content in the exhaust pipe to determine the deviation of the actual air-fuel ratio of the engine from the theoretical value. The control system adjusts the concentration of the combustible gas mixture according to the feedback signal so that the air-fuel ratio is close to the theoretical value , Thereby improving economy. Reduce exhaust pollution. The actual application is zirconia and titania sensors.

(5) Knock sensor

It is used to detect the vibration of the engine, by adjusting the electric fire advance angle control and to prevent the engine from knocking. The knock signal can be transmitted to the control system to suppress the occurrence of knock. There are mainly magnetostrictive and non-resonant piezoelectric types.

(6) Flow sensor

To measure the air intake and fuel flow to control the air-fuel ratio, there are mainly air flow sensors and fuel flow sensors. The air flow sensor detects the amount of air entering the engine to control the amount of fuel injected by the fuel injector. To get a more accurate air-fuel ratio. Practical applications include Carmen vortex, vane, and hot wire. Carmen type has no moving parts, sensitive response and high accuracy; hot wire type is easily affected by pulsation of inhaled gas and is easy to break the wire; fuel flow sensor is used to determine fuel consumption, mainly waterwheel type and ball circulation type.

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