To achieve these goals is the key to the electronic and intelligent car, prerequisite is a timely access to a variety of information, which is bound to require a large number of vehicles in a variety of sensors. Traditional sensors tend to be bulky in size and weight, and their use in cars is subject to great limitations.
Microelectromechanical system technology developed from semiconductor integrated circuit technology is becoming more and more mature. Micro-sensors are the most successful and most practical micro-electromechanical devices, including the Sensor use of micro-diaphragm mechanical deformation of the electrical signal output of the micro-pressure sensor and micro-acceleration sensor; In addition, there are micro-temperature sensors, magnetic sensors, gas sensors Etc., these micro-sensor area is mostly below 1 mm2. With the further development of microelectronic processing technology, especially nano-processing technology, sensor technology will evolve from micro-sensors to nanosensors. These miniature sensors are small enough to enable a wide range of new features, high-volume and high-precision production, low cost and easy to form large-scale and multi-function arrays that make them ideal for automotive applications.
Automotive sensors are used for automotive displays and electronic control system of various sensors collectively. It involves a lot of physical sensors and chemical sensors. These sensors either make the driver understand the state of the car parts; either for the control of the various parts of the car state. According to the role of the car can be divided into control the engine, control the chassis and the driver to provide a variety of information sensors, the composition of these sensors are fine ceramic, semiconductor materials, optical fiber and polymer film; There are analog sensors and digital sensors; according to the composition of the principle of points, there are structural, tough and complex type. For convenience, according to the control of automotive sensors to classify objects.
There are many types of sensors used on the car, and the application is very wide. Sensors in the automotive engine control, security systems, vehicle monitoring and self-diagnosis and other aspects of the application.
(A) automotive engine control sensors
The electronic control of the engine has always been considered one of the main applications of MEMS technology in the automotive industry. The engine control system sensor is the core of the entire automotive sensor, many types, including temperature sensors, pressure sensors, position and speed sensors, flow sensors, gas concentration sensors and knock sensors. These sensors provide engine operating conditions information Suction Control Valve to the engine's electronic control unit, which provides precise control of the engine's operating conditions to improve engine power, reduce fuel consumption, reduce exhaust emissions, and perform fault detection.
1. Temperature Sensor
Automotive temperature sensor is mainly used to detect the engine temperature, suction gas temperature, cooling water temperature, fuel temperature and catalytic temperature. Temperature sensors are thermistor, wirewound resistive and thermocouple resistance of the three main types. These three types of sensors have their own characteristics, and their applications are slightly different. Thermistor temperature sensor with high sensitivity, good response characteristics, but poor linearity, to adapt to lower temperature. Among them, the general temperature range of -50 ℃ ~ 30 ℃, accuracy of 1.5%, the response time of 10 ms; high temperature of 600 ℃ ~ 1000 ℃, accuracy of 5%, response time of 10ms; wirewound resistive The temperature sensor has high accuracy but low response characteristics; the thermocouple resistance type temperature sensor has high accuracy and wide temperature range, but needs to be used in conjunction with the amplifier and cold end. Other practical products are ferrite temperature sensor (temperature range of -40 ℃ ~ 120 ℃, accuracy of 2.0%), metal or semiconductor film air temperature sensor (temperature range of -40 ℃ ~ 150 ℃, accuracy 2.0%, 5%, response time of about 20 ms). 2. Pressure Sensor
The pressure sensor is the most widely used sensor in the car. It is mainly used to detect the air pressure of the air bag, the pressure of the transmission system, the pressure of the injected fuel, the oil pressure of the engine, the pressure of the inlet pipe and the fluid pressure of the air filtration system. At present, the main companies dedicated to the development and production of automotive pressure sensors are Motorola, Deco electronic equipment, Lucas Novasensor, Hi Stat, NipponDenzo, Siemens, Texas Instruments and so on.
More commonly used automotive pressure sensors are capacitive, piezoresistive, differential transformer, surface acoustic wave. Capacitive pressure sensor is mainly used to detect negative pressure, hydraulic pressure, pressure range of 20kPa ~ 100kPa, which is characterized by high input energy, good dynamic response characteristics, good environmental adaptability; piezoresistive pressure sensor performance is affected by temperature Large, need to set a temperature compensation circuit, but adapted Fuel Rail Pressure Sensor to mass production; differential transformer pressure sensor has a larger output, easy to digital output, but the anti-jamming is poor; SAW pressure sensor with small size, light weight , Low power consumption, high reliability, high sensitivity, high resolution, digital output and other characteristics, for the car suction valve pressure detection, can work steadily at high temperatures.
Germany Infineon's intelligent tire pressure sensor KP500 internal integration of the pressure and temperature sensor module, it does not need to increase the sensor module acceleration sensor, you can automatically start the car into the self-test, can measure the pressure, temperature and voltage, etc. The All functions are integrated on a 0.8μm bipolar complementary metal oxide semiconductor (BiCMOS) using surface micromachining. The only 32-bit chip identification code is stored in the electrically erasable programmable read-only memory in each sensor module. The chip identification code Temperature Sensor may be read by the synchronous serial interface and may be used to identify the position of each tire pressure sensor. In the time of receiving data, first, to check the chip identification code, if you find the chip identification code does not match, to give up the received data frame.