Sensor technology in the automotive industry

The application of automotive electronic control devices has become more and more extensive. Each electronic control device includes three parts: a sensor, an electronic control unit, and an actuator. It uses sensors to monitor the working status of the vehicle's assembly, and transmits the relevant information to the electronic control unit. After the electronic control unit analyzes, calculates, and judges, it sends instructions to the implementing agency so that the working status of the related assembly reaches the maximum. good. Automotive sensors are an important sensing electronic device in automotive components. With the increasing deployment of automobiles, the development of automotive sensors is becoming more and more advanced.

Sensors are the front end of intelligent monitoring and control by sending various parameters into computer systems. Therefore, the performance of sensors directly affects the data processing at the rear. In recent years, with the intelligentization, digitization, miniaturization, and lightness of automobiles, the demand for sensors for automobiles has become the largest in many industries. People in the industry generally believe that the key to the optimization of automotive systems is the ability to use highly reliable, high-performance sensors.

First, the characteristics of automotive sensors 1, adaptable, resistant to harsh environments The car may be driving in any region of the Earth, the environmental conditions vary greatly, both the Arctic region is extremely cold, but also like the equatorial region of the hot climate, therefore, Requires sensor with strong adaptability, can be in -40

Under the condition of ~80°C, it is not necessary to adjust the normal operation. The car may work in extreme weather conditions, sometimes filled with dust, sometimes with wind and rain, so the sensor should have a good seal, moisture resistance, corrosion resistance.

2, strong anti-interference ability In addition to being able to adapt to the external harsh environment, but also to be able to resist all kinds of interference from the engine inside. Sensors are installed in the engine room, in addition to being able to withstand the high temperature, high pressure, combustion exhaust gas corrosion of the engine, but also requires good seismic performance, to resist the strong vibration of the engine during operation, in addition, the engine will generate electromagnetic waves, Therefore, the sensor is required to have anti-jamming capability. The automotive power supply (generators, batteries, etc.) can vary in voltage from 6 to 16V, and sometimes even plus or minus 100V positive and negative high-voltage pulses, so it should also have anti-surge capability.

3, stability and reliability of the car's various parts and components are generally required to run more than 10 × 104km, and do not need to replace and adjust still meet the required technical indicators. Therefore, the sensor must have high stability and high reliability.

4, low price, adapt to mass production This requires a good consistency of the sensor, does not require complex adjustments, suitable for automated production.

Second, the application of sensors in the automotive industry 1, the pressure sensor In the practical application of automotive sensors, the earliest use of automotive pressure sensors. Can be used for many pressure detection methods, such as resistance strain gauges, capacitive sensors, inductive sensors, piezoelectric sensors and so on. Currently, the pressure sensors used in automobiles mainly include the following: manifold negative pressure sensors (used for automotive electronic ignition advance angle control and fuel injection systems); Diesel engine oil pressure sensors; transmission oil pressure sensors; brake oil pressure Sensors; shock absorber oil pressure sensors; tire pressure sensors.

Due to the wide range of applications of automotive pressure sensors in automotive systems, it has received increasing attention from related parties. At the same time, various new types of pressure sensors are emerging. For example, the high-speed shift indicator used abroad is the best time to display the high-speed shift through the light-emitting diode, which is achieved by using the fuel rail pressure sensor and the engine speed sensor.

In recent years, with the popularization of the use of microcomputers in automotive systems, various high performance new pressure sensors have begun to be used in large quantities in automobiles. The rapid development of piezoresistive semiconductor pressure sensors and resonant crystal pressure sensors.

The advantage of a semiconductor pressure sensor is that it can be mass-produced using an integrated circuit process to integrate semiconductor pressure sensors, which can significantly reduce the cost of pressure sensors. In addition, the automotive semiconductor pressure sensor is another feature that can achieve the intelligence of the sensor, this sensor can carry out the machine processing, and the minimum interface between the computer and the load, at the same time, due to zero, full, temperature The compensation and self-test functions not only improve the accuracy of the pressure sensor, but also improve the reliability of the sensor.

Resonant crystal pressure sensor is mainly used as a suction negative pressure sensor for automobiles. Its remarkable feature is that it can still work stably at high temperatures. With the improvement of the properties of thin film dielectrics in the future, the performance of the sensors will also take a big leap forward.

In addition, by using a compatible technology that combines active piezoelectric and pyroelectric thin films with integrated circuits, it is also possible to fabricate multifunctional automotive sensors, and it is also possible to solve the problem that piezoelectric sensors are difficult to integrate.

2. Air flow sensor An important control content in the electronic control system of the engine is the best air-fuel control. To achieve this goal, an accurate measurement of the intake air flow of the engine must be performed. Commonly used air flow sensors include air flow meter, Karman vortex air flow meter, hot air flow meter and hot film air flow meter.

The damper type air flowmeter has a simple structure and high reliability, but has a large intake resistance, a slow response and a large volume; and the hot wire type air flowmeter has not only a reliable operation but also has a fast response due to no moving parts. The disadvantage is that the velocity distribution is not The average error is larger. Although the working principle of the hot-film air flow meter is similar to that of the hot-wire air flow meter, since the hot-film type sensor does not use the platinum wire as the hot wire, the hot wire resistance, the compensation resistance, etc. are made by the thick film process, and the same ceramic base is used. On the chip, the heating element is not directly subjected to the force generated by the air flow, thereby increasing the strength of the heating element, not only improving the reliability of the air flow meter, but also reducing the error and improving the performance.

3. The throttle sensor is used to convert the throttle opening into a voltage signal and control the injection quantity through the ECU. There are two kinds of switch-type throttle position sensors and linear throttle sensors. The switch-type throttle position sensor has a simple structure, but its output is discontinuous. In addition to the above three, sensors used for electronic control of automotive engines include oxygen sensors, temperature sensors, knock sensors, crankshaft position sensors, and rotational speed sensors.

Any modern automobile system or device that uses electronic control cannot be separated from sensors such as automatic transmissions, anti-lock brake systems, and anti-skid systems. Especially in recent years, there are more and more vehicle electronic devices, such as security alarm devices, communication devices, entertainment devices, and assisted driving devices used for improving comfort and reducing fatigue. Of course, home-made cars have only just begun in the electronic control technology, mainly focused on the electronic control of the engine. Because of this, automotive sensors will have a broader space for development in our country.