Sensors For Engine Control

There are many types of sensors used for engine control, including temperature sensors, pressure sensors, speed and angle sensors, flow sensors, position sensors, gas concentration sensors, knock sensors, etc. These types of sensors are the core of the entire engine, and their use can improve engine power, reduce fuel consumption, reduce exhaust emissions, reflect faults, etc. Due to their operation in harsh environments such as engine vibration, gasoline vapor, sludge, and muddy water, their resistance to harsh environmental technical indicators are higher than ordinary sensors. There are many requirements for their performance indicators, among which the most critical are measurement accuracy and reliability. Otherwise, the errors caused by sensor detection will ultimately lead to engine control system failure or malfunction.
1. Temperature sensor: mainly detects engine temperature, intake gas temperature, cooling water temperature, fuel temperature, engine oil temperature, catalytic temperature, etc. The temperature sensors used in practical applications mainly include wired wound resistance type, thermistor type, and thermocouple type. The wire wound resistance temperature sensor has high accuracy, but poor response characteristics; Thermistor type sensors have high sensitivity and good response characteristics, but poor linearity and are suitable for low temperatures; The thermocouple type has high accuracy and a wide temperature measurement range, but needs to consider amplifier and cold junction treatment issues.
2. Pressure sensor: mainly detects intake manifold absolute pressure, vacuum, atmospheric pressure, engine oil pressure, brake oil pressure, tire pressure, etc. There are several types of pressure sensors used in vehicles, including capacitive, varistor, capsule 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; Varistor type is greatly affected by temperature and requires additional temperature compensation circuits, but is suitable for mass production; LVDT type has a large output, which is easy to digital output, but has poor vibration resistance; The SAW type sensor has the characteristics of small size, light weight, low power consumption, strong reliability, high sensitivity, high resolution, and digital output, making it an ideal sensor.
3. Speed, angle, and vehicle speed sensors: mainly used to detect crankshaft angle, engine speed, vehicle speed, etc. There are mainly generator type, reluctance type, Hall effect type, optical type, vibration type, etc.
4. Oxygen sensor: The oxygen sensor is installed in the exhaust pipe, measuring the oxygen content in the exhaust pipe, determining the deviation between the actual air fuel ratio of the engine and the theoretical value. The control system adjusts the concentration of the combustible mixture based on the feedback signal, making the air fuel ratio close to the theoretical value, thereby improving economy and reducing exhaust pollution. The practical applications are zirconia and titanium oxide sensors.
5. Flow sensor: It measures the intake air and fuel flow to control the air fuel ratio, mainly including air flow sensors and fuel flow sensors. The air flow sensor detects the amount of air entering the engine and controls the injection volume of the fuel injector to obtain a more accurate air fuel ratio. The practical applications include the Karman vortex type, blade type, and hot wire type. Carmen type with no movable components, sensitive response, and high accuracy; The hot wire type is easily affected by the pulsation of inhaled gas and is prone to wire breakage; The fuel flow sensor is used to determine fuel consumption. There are mainly water wheel type and ball circulation type.