With the development of electronic technology, the degree of electronic electronics has been continuously improved, and the usual mechanical systems have been difficult to solve some problems related to the functional requirements of automobiles, and have been replaced by electronic control systems. The function of the sensor is to quantify the component that provides a useful electrical output signal according to the specified measured size, that is, the transducer that converts the physical and chemical quantities of light, time, electricity, temperature, pressure, and gas into signals. As a key component of the automotive electronic control system, the sensor directly affects the technical performance of the car. At present, there are about 10-20 sensors on the average car and more in the luxury limousine. These sensors are mainly distributed in the engine control system, chassis control system and body control system.
First, the engine control sensor
There are many types of sensors for engine control, including temperature sensors, pressure sensors, speed and angle sensors, flow sensors, position sensors, gas concentration sensors, knock sensors, and the like. These sensors are the core of the entire engine, which can improve engine power, reduce fuel consumption, reduce exhaust gas, reflect faults, etc. Because they work in harsh environments such as engine vibration, gasoline vapor, sludge and muddy water, they are resistant to harsh conditions. Environmental technology indicators are higher than the average sensor. There are many requirements for their performance indicators, the most critical of which is measurement accuracy and reliability, otherwise the error caused by sensor detection will eventually lead to engine control system failure or failure.
1. Temperature sensor: mainly detects engine temperature, suction gas temperature, cooling water temperature, fuel temperature, oil temperature, catalytic temperature, etc. The practical temperature sensors are mainly wired, resistive, thermistor and thermocouple. The wirewound resistance temperature sensor has high precision, but the response characteristics are poor. The thermistor sensor has high sensitivity and good response characteristics, but the linearity is poor, and the applicable temperature is low. The thermocouple type has high precision and wide temperature range, but it needs Consider amplifier and cold junction handling issues.
2. Pressure sensor: mainly detects the absolute pressure of the intake manifold, vacuum, atmospheric pressure, engine oil pressure, brake oil pressure, tire pressure and so on. There are several types of pressure sensors for vehicles. There are capacitive, varistor, diaphragm-driven variable inductance (LVDT) 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 affected by temperature, and a temperature compensation circuit is required, but it is suitable for mass production; LVDT type has large output and is easy to digital. Output, but the vibration resistance is poor; SAW type is a kind of ideal sensor with small size, light weight, low power consumption, high reliability, high sensitivity, high resolution and digital output.
3. Speed, angle and vehicle speed sensor: mainly used to detect crank angle, engine speed, vehicle speed and so on. There are mainly generator type, magnetoresistive type, Hall effect type, optical type, vibrating type and the like.
4. Oxygen sensor: The oxygen sensor is installed in the exhaust pipe, measures the oxygen content in the exhaust pipe, determines the deviation between the actual air-fuel ratio of the engine and the theoretical value, and the control system adjusts the concentration of the combustible mixture according to the feedback signal, making it empty. The fuel ratio is close to the theoretical value, thereby improving economy and reducing exhaust pollution. Practical applications are zirconia and titanium oxide sensors.
5. Flow sensor: Determine the air intake and fuel flow to control the air-fuel ratio, mainly air flow sensor and fuel flow sensor. The air flow sensor detects the amount of air entering the engine to control the fuel injection amount of the injector to obtain a more accurate air-fuel ratio. The practical application includes a card door vortex type, a vane type, and a hot line type. The Carmen type has no moving parts, is sensitive and has high precision; the hot wire type is susceptible to the pulsation of the suction gas and is easy to break; the fuel flow sensor is used to determine the fuel consumption. There are mainly waterwheel type and ball circulation type.
6. Knock sensor: It can transmit the knock signal to the control system to suppress the occurrence of knock. There are mainly magnetostrictive and non-resonant piezoelectric types.
Second, the chassis control sensor
Chassis control sensors are sensors distributed in the transmission control system, suspension control system, power steering system, and anti-lock braking system. They function differently in different systems, but the working principle is the same as that in the engine. The following types of sensors:
1. Transmission control sensor: It is mostly used for the control of electronically controlled automatic transmission. It is based on the information obtained by the vehicle speed sensor, the acceleration sensor, the engine load sensor, the engine speed sensor, the water temperature sensor and the oil temperature sensor. The information is processed to enable the electronic control device to control the shift point and the torque converter to lock the maximum power. And maximum fuel economy.
2. Suspension system control sensors: mainly include vehicle speed sensor, throttle opening sensor, acceleration sensor, vehicle height sensor, steering wheel angle sensor, etc. The vehicle height is automatically adjusted based on the detected information, and the change in the posture of the vehicle is suppressed, thereby achieving control of vehicle comfort, steering stability, and driving stability.
3. Power steering system sensor: It is based on the vehicle speed sensor, engine speed sensor, torque sensor, etc. to make the power steering electronic control system realize steering steering light, improve response characteristics, reduce engine loss, increase output power, save fuel and so on.
4. Anti-lock brake sensor: It is based on the wheel angular velocity sensor to detect the wheel speed. When the slip ratio of each wheel is 20%, the brake oil pressure is controlled, the braking performance is improved, and the maneuverability and stability of the vehicle are ensured. .
Third, the body control sensor
The main purpose of using such sensors is to improve the safety, reliability and comfort of automobiles, mainly including various temperature sensors, air volume sensors, sunshine sensors, etc. used in automatic air conditioning systems; acceleration sensors in airbag systems; brightness control Medium light sensor; ultrasonic sensor in dead angle alarm system; image sensor.
Fourth, the research and development trend of vehicle sensors
Due to the important role of sensors in electronic control systems, countries around the world attach great importance to their theoretical research, new material applications, and product development.
Diamond has good heat resistance and high thermal stability. Carbonization begins on the surface at 1200 °C or higher in vacuum, and carbonization starts at 600 °C in the atmosphere. Using this characteristic, a thermal sensor suitable for high temperature is produced. It is used for temperature monitoring and control from room temperature to 600 °C, and is suitable for use in harsh environments with high temperature and corrosive gas. It has stable performance and long service life, and can be used for high temperature measurement in engines. In addition, the diamond has a high deformation rate at high temperatures, and this feature can be used to produce vibration sensors and acceleration sensors for use in high temperature environments. Combined with other material diaphragms, it can be used as a high temperature, corrosion resistant and sensitive pressure sensor for vibration detection and engine cylinder pressure measurement.
Due to its strong anti-interference, high sensitivity, light weight and small size, the optical fiber sensor is widely used in telemetry. At present, there are many mature products, such as optical fiber torque sensor, temperature, vibration, pressure, flow and other sensors.
At the same time of development and utilization of new materials, due to the development of microelectronics technology and micromachining technology, sensors are becoming more miniaturized, multi-functional, and intelligent. Miniaturized sensors use micromachined processing technology to package micron-scale sensitive components, signal conditioners, and data processing devices on a single chip. Due to its small size, low price and easy integration, it can improve the system test accuracy. For example, by integrating the miniature pressure sensor and the miniature temperature sensor, and measuring the pressure and temperature, the temperature in the pressure measurement can be eliminated by the on-chip operation. influences. At present, many miniature sensors have been introduced, such as pressure sensors, acceleration sensors, and silicon acceleration sensors for collision avoidance. Embedding a miniature pressure sensor in the car's tires maintains proper inflation and avoids over- or under-inflation, saving fuel by 10%. Multi-function enables the sensor to detect two or more characteristic parameters simultaneously. Smart sensors are intelligent because they have a dedicated computer.
In addition, issues such as sensor response time, output and computer interface are also important research topics. With the development of electronic technology, the technology of automotive sensors will be perfected.
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