With the traditional mechanical system is gradually replaced by electronic control system, at present, the ordinary car is equipped with dozens to nearly a hundred sensors, luxury cars are more, these sensors are mainly distributed Sensor in the engine control system, chassis control system and body Control system. The advantages and disadvantages of the sensor also directly affect the system performance.
There are many kinds of engine sensors, including temperature sensors, pressure sensors, rotary sensors, flow sensors, position sensors, concentration sensors, knock sensors and so on. This type of sensor is the core of the entire vehicle sensor, which can improve the engine power, reduce fuel consumption, reduce emissions, reflect the fault, etc., because of its work in the engine vibration, gasoline steam, sludge, water and other harsh environments, so they Of the harsh environmental technical indicators to be higher than the general sensor. There are many requirements for their performance indicators, the most critical of which is the measurement accuracy and reliability, otherwise the error caused by the sensor detection will eventually lead to engine control system failure or failure.
The knock sensor detects detonation or combustion noise under various operating conditions of the engine to avoid engine malfunction.
(1) temperature sensor: the main detection of engine temperature, suction gas temperature, cooling water temperature, fuel temperature, catalytic temperature, etc., they are converted into electrical signals, thus controlling the nozzle opening time and duration to ensure that the supply of the engine The best mixture and achieve the effect of exhaust purification. The actual application of Suction Control Valve the temperature sensor mainly wirewound resistive, thermistor and thermocouple type. Wire-type resistive temperature sensor with high accuracy, but the response characteristics are poor; thermal sensor high sensitivity, good response characteristics, but poor linearity, suitable for low temperature; thermocouple sensor with high accuracy, wide temperature range, But need to consider the amplifier and cold-end processing problems.
(2) pressure sensor: the main detection of negative pressure cylinder to control the ignition and fuel injection; detection of atmospheric pressure, thus controlling the time and space ratio of climbing; detection of cylinder pressure, thus controlling the ignition advance angle; detection of exhaust gas recirculation flow, Brake oil pressure, tire air pressure, etc., and respond to the relevant amount. There are a number of automotive pressure sensors, the application of a more capacitor, piezoresistive, differential transformer (LVDT), surface elastic wave (SAW). Capacitive sensor with high input energy, good dynamic response, good environmental adaptability and other characteristics; piezoresistive temperature by the impact of large, need to set the temperature compensation circuit, but for mass production; LVDT type has a larger output, easy to digital output SAW type has Temperature Sensor the characteristics of small volume, light weight, low power consumption, high reliability, high sensitivity, high resolution and digital output. It is an ideal sensor.
(3) Rotary sensor: mainly used to detect the crank angle, the number of engine revolutions, throttle opening, speed, etc., to control the ignition advance angle, fuel dosage and injection time, the main products are generators, The effect type, the optical type, the vibration type and so on.
(4) Oxygen sensor: to detect the air-fuel ratio in the exhaust gas, to the fuel supply system to send a negative feedback signal to correct the fuel injection pulse, so that the air-fuel ratio adjusted to the theoretical value, in order to achieve the desired exhaust purification effect, commonly used zirconia and Titanium oxide sensor. The sensors are mainly distributed in the engine control system, chassis control system and body control system. The advantages and disadvantages of the sensor also directly affect the system performance.
(5) flow sensor: the intake air flow and fuel flow to control the air-fuel ratio. There are air flow sensors and fuel flow sensors. Air flow sensor to detect the amount of air into the control of the electronic injector fuel injection to get a more accurate air-fuel ratio, the actual application of the main products are Kalman vortex, leaf type, hotline. The fuel flow sensor is used to detect the fuel flow rate to calculate the fuel consumption of the vehicle. The main products Pressure Sensor are the water tanker. The fuel flow sensor is used to detect the fuel flow rate. The fuel flow is used to detect the fuel flow rate. Type, ball circulation.
(6) knock sensor: to detect the vibration of the engine, and according to the detected detonation signal appropriate to adjust the ignition time, the main products are magnetostrictive and piezoelectric.
Chassis control sensors are sensors located in the transmission control system, suspension control system, power steering system, anti-lock braking system, they are different in different systems, but the working principle and the engine is the same sensor, the main There are several forms of sensors.
(1) transmission control sensors: mainly speed sensor, acceleration sensor, engine load sensor, engine speed sensor, clutch sensor, water temperature sensor, oil temperature sensor. These sensors detect the information obtained by the control of the electronic control device to control the shift point and torque converter lock, to achieve maximum power and maximum fuel economy.
(2) Suspension system control sensor: There are speed sensor, throttle opening sensor, acceleration sensor, body height sensor, steering wheel angle sensor. The system automatically adjusts the vehicle height according to the information detected by these sensors, restrains the change of the vehicle posture, and realizes the control of the vehicle comfort, the handling stability and the driving stability.
(3) power steering system with sensors: the main speed sensor, the engine speed sensor, torque sensor, the use of these sensors to power steering control system to achieve steering operation to improve Speed Sensor the response characteristics, reduce engine wear and increase output power, Save fuel and so on.
(4) anti-lock brake sensor is mainly the use of wheel angular velocity sensor to detect the wheel speed, the wheel slip rate of 20% when the control brake oil pressure, improve braking performance, to ensure vehicle handling and stability.
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The main purpose of this type of sensor is to improve the safety, reliability and comfort of the vehicle. The technical requirements for the harsh environment are not as good as that of the engine and the chassis, and the general industrial sensor can be improved by using the sensor The Mainly used in automatic air conditioning system in a variety of temperature sensors, air volume sensors, sunshine sensors, brake door lock system in the vehicle speed sensor, the airbag system in the acceleration sensor, brightness control in the light sensor, dead angle alarm system Ultrasonic sensors, image sensors and so on.
4 automotive sensor research and development trends
Because of the importance of the sensor in the electronic control system, in a sense, the competition of the advanced automobile is the competition of the sensor, and the countries of the world attach great importance to its theoretical research, new material application and product development. Diamond heat resistance is good, high heat stability, in the vacuum above 1200 ℃ its surface began to appear in the atmosphere, but also in the atmosphere above 600 ℃ began to carbonization, the use of this feature, made for high temperature thermal sensors, From room temperature to 600 ℃ within the temperature monitoring and control, and for high temperature and corrosive gas in the harsh environment, stable performance, long life, can be used for high temperature measurement in the engine. In addition, diamond deformation rate Throttle Position Sensor at high temperatures is very high, the use of this feature can be used in high temperature environment, the use of vibration sensors and acceleration sensors. Combined with other materials, the diaphragm can be used as a high temperature, corrosion resistance, high sensitivity pressure sensor for vibration detection and engine, cylinder pressure and other measurements.
Optical fiber sensor because of its strong anti-interference, high sensitivity, light weight, small size, suitable for telemetry and other characteristics are being widely accepted. At present, many mature products come out, such as fiber torque sensor, and temperature, vibration, pressure, flow and other sensors. In the development and utilization of new materials at the same time, due to microelectronics technology and micro-machining technology development, the sensor is moving in the miniaturization, multi-functional, intelligent direction. The miniaturized sensor utilizes micromachining technology to package micron-sized sensitive components, signal conditioner, and data processing devices on a single chip. Because of its small size, low cost, easy integration and other characteristics, can improve the system test accuracy, such as the micro-pressure sensor and micro-temperature sensor integrated together, while measuring the pressure and temperature, through the chip operation to eliminate the pressure measurement Temperature effect. At present, many micro-sensors are available, such as pressure sensors, accelerometers, silicon accelerometers for crash protection, and so on. It is said that the embedded miniature pressure sensor in the car tire can maintain proper inflation, to avoid excessive Pressure Switch or insufficient inflation, which can save fuel 10%. The versatility allows the sensor to simultaneously detect two or more characteristic parameters. The smart sensor with a dedicated computer, which has intelligent features.
In addition, the sensor response time, the output and the computer interface and other issues is also an important research topic. With the development of electronic technology, vehicle sensor technology will tend to improve.