Vehicle sensors are the input devices of the automobile computer system. It converts various operating conditions of the automobile, such as vehicle speed, temperature of various media, engine operating conditions, etc., into electrical signals and sends them to the computer so that the engine is at its best. Working status. There are many automotive sensors. When judging the fault of the sensor, you should not only consider the sensor itself, but the entire circuit where the fault occurs. Therefore, when looking for faults, in addition to checking the sensor, the wiring harness, connectors, and related circuits between the sensor and the electronic control unit should also be checked.
One of the characteristics of the development of automobile technology is that more and more parts adopt electronic control. According to the function of the sensor, it can be classified into sensors that measure temperature, pressure, flow, position, gas concentration, speed, brightness, dry humidity, distance and other functions. They each perform their duties. Once a sensor fails, the corresponding device will work. It will be abnormal or even not working. Therefore, the role of the sensor in the car is very important.
Automotive sensors used to be purely on engines, but have been extended to chassis, body and light electrical systems. There are more than 100 kinds of sensors used in these systems. Among the wide range of sensors, the common ones are:
Intake pressure sensor: It reflects the change of absolute pressure in the intake manifold, and provides a reference signal for calculating the fuel injection duration to the ECU (engine electronic control unit);
Air flow meter: Measure the amount of air drawn by the engine and provide it to the ECU as a reference signal for fuel injection time;
Throttle position sensor: Measure the angle of throttle opening and provide it to ECU as a reference signal for fuel cutoff, fuel/air ratio control, and ignition advance angle correction;
Crankshaft position sensor: detects the crankshaft and engine speed, and provides it to the ECU as a reference signal for determining the ignition timing and working sequence;
Oxygen sensor: detects the oxygen concentration in the exhaust gas and provides it to the ECU as a reference signal to control the fuel/air ratio near the optimal value (theoretical value);
Intake air temperature sensor: detects the intake air temperature and provides it to the ECU as a basis for calculating air density;
Coolant temperature sensor: detects the temperature of the coolant and provides engine temperature information to the ECU;
Knock sensor: It is installed on the cylinder to specifically detect the engine’s knocking situation, and is provided to the ECU to adjust the ignition advance angle according to the signal.
These sensors are mainly used in transmission, steering, suspension and ABS.
Transmission: There are vehicle speed sensors, temperature sensors, shaft speed sensors, pressure sensors, etc., and the direction indicators include rotation angle sensors, torque sensors, and hydraulic sensors;
Suspension: There are vehicle speed sensor, acceleration sensor, vehicle height sensor, roll angle sensor, rotation angle sensor, etc.;
Let’s get to know the main sensors on the car.
The air flow sensor converts the inhaled air into an electric signal and sends it to the electronic control unit (ECU) as one of the basic signals for determining fuel injection. According to different measurement principles, it can be divided into four types: rotary vane air flow sensor, Karman vortex air flow sensor, hot wire air flow sensor and hot film air flow sensor. The first two are volume flow type, and the latter two are mass flow type. Mainly use two kinds of hot wire air flow sensor and hot film air flow sensor.
The intake pressure sensor can measure the absolute pressure in the intake manifold according to the load state of the engine, and convert it into an electrical signal and a speed signal and send it to the computer as a basis for determining the basic fuel injection volume of the injector. The semiconductor piezoresistive intake pressure sensor is widely used.
The throttle position sensor is installed on the throttle to detect the opening of the throttle. It is linked with the throttle through a lever mechanism to reflect the different operating conditions of the engine. This sensor can detect the different working conditions of the engine and input it into the electronic control unit (ECU) to control different fuel injection quantities. It has three types: switch contact type throttle position sensor, linear variable resistance type throttle position sensor, comprehensive throttle position sensor.
Crankshaft position sensor, also called crankshaft angle sensor, is the most important sensor in computer-controlled ignition system. Its function is to detect top dead center signal, crankshaft angle signal and engine speed signal, and input it into the computer, so that the computer can press the cylinder The best ignition timing command is issued in the ignition sequence. There are three types of crankshaft position sensors: electromagnetic pulse type crankshaft position sensor, Hall effect type crankshaft position sensor, photoelectric effect type crankshaft position sensor. Different types of crankshaft position sensors have different control methods and control accuracy. The crankshaft position sensor is generally installed on the side of the crankshaft pulley or sprocket, and some are installed on the front end of the camshaft, and some are installed on the distributor.
The knock sensor is installed on the cylinder block of the engine to monitor the knock of the engine at any time. There are two types of resonance type and non-resonance type.