Detailed classification and function of automotive sensors-EEWORLD

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Classification and function of automobile sensors

As the "sensory organs" of automobiles, automotive sensors are widely used in various electronic control systems of engines, chassis and bodies in automotive electronic control. Automobile sensors are responsible for collecting and transmitting information. After the electronic control unit processes the information, it sends commands to the actuator to implement electronic control. It can timely identify changes in the outside world and changes in the system itself, and then control the work of the system itself based on the changed information.

Pressure and speed related sensors

Pressure sensors mainly include semiconductor piezoresistors, capacitors, variable inductors with diaphragm transmission, and surface elastic waves. The first two are widely used, with the characteristics of small size, high precision, low cost, good response performance, strong versatility, and wide detection range.

Manifold Absolute Pressure Sensor

Used in the D-type EFI system, unlike the air flow sensor, the intake manifold sensor adopts an indirect measurement method, that is, it measures the relative value of the absolute pressure in the intake manifold according to the change of engine load, and then calculates the engine intake volume.

Boost pressure sensor

It is usually installed on a supercharged engine to detect the working condition of the turbocharger, and convert the change into an electrical signal, which is then provided to the electronic control unit (ECU) for the ECU to control the injection pulse and the size of the supercharger pressure.

Cylinder combustion pressure sensor

There are two types of cylinder combustion pressure sensors: one is a direct type sensor with the side of the fuel chamber as the pressure surface, abbreviated as PDS; the other is a gasket-shaped pressure sensor fastened to the spark plug, abbreviated as PGS. The former can realize linear detection of combustion chamber pressure, and the latter has good assembly performance and is suitable for higher-precision knock control, misfire detection, etc.

The cylinder combustion pressure sensor is used to provide the cylinder combustion pressure signal to the ECU. The control system can obtain a lot of information from the combustion pressure sensor to control the engine in a timely manner, such as determining the optimal ignition time and valve timing.

Tire pressure sensor

The tire pressure sensor uses temperature difference compensation correction method to generate a series of electronic signals according to the changes of tire pressure, tire temperature and battery voltage, and provide them to the ECU to measure the tire pressure in time. Its working pressure can reach up to 1380kPa, the working temperature is -40~125 degrees Celsius, and the accuracy is not less than 1%.

Wheel speed sensor

It is used to detect wheel speed and provide the signal to the ABS ECU, which obtains the vehicle speed signal parameters after processing. Wheel speed sensors are usually installed on wheels, reducers or gearboxes, and generally use electromagnetic induction or photoelectric induction principles to obtain signals. The number of installations depends on the system layout and control method.

Deceleration sensor

Commonly used deceleration sensors are mainly differential voltage deceleration sensors and switch deceleration sensors. The former uses the movement of the sliding parts when the vehicle decelerates to detect the deceleration signal, while the latter uses the moving position of the inertial parts when the vehicle decelerates to sense the deceleration. The deceleration sensor, also known as the G sensor, is used to detect wheel acceleration or braking deceleration, and is used as an auxiliary signal for threshold control, and detects and controls the braking process on low adhesion roads.

Engine temperature related sensors

The function of the engine temperature sensor is to convert the temperature changes of gas or liquid into electrical signals and provide them to the ECU.

Water temperature sensor

Installed on the cylinder, it is used to detect the temperature information of the engine cooling water and convert the information into electrical signals and provide them to the engine electronic control unit.

Intake air temperature sensor

The engine intake air temperature sensor is installed on the air flow sensor in the L-type EFI system and in the air filter housing or surge tank in the D-type EFI system to provide the engine electronic control unit with information on the engine intake air temperature.

Fuel temperature sensor

Used in diesel engine electronic control distribution pump fuel injection system, the user provides the engine electronic control unit with fuel temperature information to achieve precise control of the injection amount.

Position and speed related sensors

The throttle position sensor, crankshaft position sensor, vehicle speed sensor, and accelerator pedal position sensor are used to provide various position information to the ECU.

Throttle Position Sensor

Installed on the throttle body, it can convert the throttle opening, idle speed, high load and other information into electrical signals and provide them to the ECU. There are two types of throttle position sensors: linear output type and switch output type. In comparison, the latter has poor detection performance, but it has a simple structure and is cheap. Some EFI systems are equipped with both types of throttle position sensors, using the switch output type sensor to detect the engine idle speed and full load status; and the linear output type sensor is used to detect the throttle opening of the entire vehicle.

Crankshaft Position Sensor

It is used to provide the ECU with engine crankshaft position, rotation angle position signal, piston stroke position signal and engine speed signal. There are three types: magnetoelectric, photoelectric and Hall. The first two are usually installed in the distributor and rotate with the distributor, and the latter is installed at the front end of the crankshaft. Magnetoelectric sensors and Hall sensors are widely used because of their strong anti-interference ability and good recognition ability at high speed.

Vehicle speed sensor

Installed on the transmission output shaft or the final reducer, it provides the electronic control unit with a vehicle speed signal. The structure and principle of this sensor are very similar to those of the crankshaft position sensor.

Accelerator pedal position sensor

Applicable to direct injection engines, it provides the ECU with information on load size, load range, acceleration and deceleration. Based on this information, the ECU determines the amount of fuel injected in the stratified combustion zone of the engine (direct injection engines have two combustion modes: stratified combustion and uniform combustion).

Exhaust and purification related sensors

Exhaust purification sensors are used to convert relevant information in the exhaust gas into electrical signals and provide them to the ECU.

Oxygen Sensor

Oxygen sensors are divided into two categories: zirconium oxide and titanium oxide. They are installed on the exhaust pipe and are used to feed back the actual air-fuel ratio signal to the ECU, so as to converge the actual air-fuel ratio within a narrow range near the theoretical value to form a closed-loop control. In comparison, titanium oxide oxygen sensors have the characteristics of simple structure, small size and low cost, but their resistance changes to a greater extent with temperature changes, so when used at high temperatures, certain temperature compensation measures are usually taken.

Exhaust Gas Recirculation Displacement Sensor

It is mainly used to provide the ECU with the opening information of the exhaust gas recirculation control valve, so as to control the working conditions of the exhaust gas treatment system accordingly.

Differential Pressure Sensors

Installed downstream of the particulate trap, it is used to provide the ECU with the particulate trap differential pressure information so that the particles in the particulate trap can be burned off at high temperature in a timely manner to prevent the exhaust back pressure from increasing.

NOx Sensor

It is used to provide the ECU with NOx concentration information in the exhaust gas after-treatment system so as to control the working condition of the after-treatment SCR system accordingly.

Exhaust temperature sensor

It is usually installed near the three-way catalytic converter to detect its operating temperature and convert this information into electrical signals and provide them to the ECU.

EGR temperature sensor

It is usually installed downstream of the EGR valve to detect the temperature of the EGR and convert the signal into an electrical signal before providing it to the ECU.

Automatic air conditioning system sensor

The sensors of the automobile automatic air-conditioning electronic control system are mainly used for temperature detection, and mainly use thermistors with negative temperature coefficients.

Interior temperature sensor

Usually installed on the lower side of the dashboard, it is a thermistor temperature sensor with a negative temperature coefficient characteristic, used to provide the temperature signal inside the vehicle to the air conditioning ECU.

External ambient temperature sensor

The outside temperature sensor is also a thermistor temperature sensor with a negative temperature coefficient characteristic, usually installed on the lower side of the front bumper of the vehicle. It is used to provide the temperature signal outside the vehicle to the air conditioning ECU.

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