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Home > Mall Dynamic > Function, Working Principle, Circuit, Fault Inspection OF Crankshaft Position Sensor
The role of the crankshaft position sensor is to determine the position of the crankshaft, that is, the Angle of the crankshaft and the engine speed. It usually works with a camshaft position sensor to determine the basic ignition time. We all know that the engine starts firing at the end of the compression stroke, so how does the engine computer know which cylinder to fire? It is calculated by the signal of the crankshaft position sensor and the camshaft position sensor, through the crankshaft position sensor, you can know which cylinder piston is at TDC, through the camshaft position sensor, you can know which cylinder piston is in the compression stroke. This way, the engine computer knows when to fire which cylinder.
The crankshaft position sensor is usually installed at the front end of the crankshaft (at the pulley) near the big flywheel or in the middle of the crankshaft, and early models are also installed in the distributor, which is one of the most important sensors in the control system. Its role is: to detect the engine speed, so it is also called the speed sensor; Detecting the top dead center position of the piston, so it is also known as the top dead center sensor, including detecting the top dead center signal of each cylinder used to control the ignition and the top dead center signal of the first cylinder used to control the sequential injection of oil.
There are three main types of crankshaft sensors: magnetoelectric induction, Hall effect and photoelectric.
The magnetoelectric induction speed sensor and the crankshaft position sensor are installed in the distributor in the upper and lower layers. The sensor consists of a permanent magnet induction detection coil and a rotor (timing rotor and speed rotor), which rotates with the distributor shaft. The timing rotor has a variety of forms such as one, two or four teeth, and the speed rotor has 24 teeth. The permanent magnet induction detection coil is fixed on the distributor body. If the speed sensor signal and crankshaft position sensor signal are known, as well as the working sequence of each cylinder, the crankshaft position of each cylinder can be known. Magnetic induction speed sensors and crankshaft position sensors can also be mounted on the crankshaft or camshaft rotor signal disk.
Hall effect speed sensor and crankshaft position sensor are signal generators using Hall effect. The Hall signal generator is installed in the distributor, coaxial with the distributor head, and is fixed on the distributor board as a whole by the packaged Hall chip and permanent magnet. The number of notches on the trigger impeller is the same as the number of engine cylinders. When the blade on the trigger impeller enters between the permanent magnet and the Hall element, the magnetic field of the Hall trigger is bypassed by the blade, and the Hall voltage is not generated, and the sensor has no output signal. When the notched part on the trigger impeller enters between the permanent magnet and the Hall element, the magnetic force line enters the Hall element, the Hall voltage rises, and the sensor outputs the voltage signal.
The photoelectric crankshaft position sensor is generally installed in the distributor and consists of a signal generator and a signal disk with a light hole. The signal plate rotates with the distributor shaft, and there are 360 lithographic gaps in the outer ring of the signal plate to generate a signal of 1 ° of the crankshaft Angle; There are 6 optical holes spaced 60 ° apart slightly to generate a signal of 120 ° crankshaft Angle, of which 1 optical hole is wider to generate a signal relative to the top dead center of the 1 cylinder. The signal generator is mounted on the distributor housing and consists of two light-emitting diodes, two photosensitive diodes and a circuit. The light-emitting diode is facing the photosensitive diode. The signal disk is located between the light-emitting diode and the photosensitive diode, and because there is a light hole on the signal disk, it produces alternating changes in light transmission and light blocking. When the light from the light-emitting diode hits the photosensitive diode, the photosensitive diode produces a voltage; When the LED beam is blocked, the photodiode voltage is 0. These voltage signals are partially shaped and amplified by the circuit, that is, the signals when the crankshaft Angle is 1 ° and 120° are transmitted to the electronic control unit, and the electronic control unit calculates the engine speed and crankshaft position according to these signals.
Typically, the crankshaft position sensor works with the camshaft position sensor to determine the basic ignition moment. In the automobile control system, the crankshaft position sensor is one of the most important sensors, its main role includes detecting the engine speed, so it is also called the speed sensor; The detection of the piston TDC position, therefore also known as the TDC sensor, includes the detection of the TDC signal for each cylinder to control ignition and the TDC signal for the first cylinder to control sequential fuel injection. There are three main types of crankshaft sensors: magnetoelectric induction, Hall effect and photoelectric.
The role of the crankshaft position sensor is very important, it can detect the engine speed, so as to determine the fuel injection and ignition advance Angle. In addition, it can also detect the reference position of the engine reference cylinder, discriminate the cylinder sequence, and further determine any position of the piston. The crankshaft position sensor can also detect the Angle of rotation of the crankshaft to determine any position of piston operation and determine the time of ignition and fuel injection. In addition to controlling fuel injection and ignition, it is also used for idle speed control, exhaust gas recirculation control, fuel evaporation control, etc.
In short, the crankshaft position sensor plays a crucial role in the automotive control system, its role is not only to determine the position of the crankshaft, but also to detect the engine speed, determine the amount of fuel injection and ignition advance Angle, and detect the piston top dead center position. Therefore, it is essential for the proper operation and performance of the car.
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