Structure and working principle of Hall crankshaft position sensor
(1) Hall crankshaft position sensor with trigger blade
The Hall Crankshaft Position Sensor of American General Company is installed at the front end of the crankshaft and adopts the trigger blade structure. At the front end of the engine crankshaft pulley, there are two internal and external signal wheels with trigger blades, which rotate together with the crankshaft. 18 trigger blades and 18 windows are evenly distributed on the outer edge of the outer signal wheel, and the width of each trigger blade and window is 10 arc length; There are three trigger blades and three windows on the outer edge of the internal signal wheel. The widths of the three trigger blades are different, which are 100, 90 and 1 10 respectively, and the widths of the three windows are also different, which are 20, 30 and 10 respectively. Due to the installation position of the inner signal wheel, the leading edge of the trigger blade with the width of 100 arc length is 75 before the top dead center (TDC) of 1 cylinder and the fourth cylinder, and the leading edge of the trigger blade with the arc length of 90 is 75 before the top dead center of the sixth cylinder and the third cylinder, with the arc length of 1 10.
Hall signal generator consists of permanent magnet, magnetic conductive plate and Hall integrated circuit. Hall signal generators are installed on the sides of the inner and outer signal wheels respectively. When the signal wheel rotates, whenever the blade enters the air gap between the permanent magnet and the Hall element, the magnetic field in the Hall integrated circuit is bypassed (or magnetically isolated) by the trigger blade, and no Hall voltage is generated at this time; When the trigger blade leaves the air gap, the magnetic relaxation of the permanent magnet 2 passes through the Hall element through the magnetic conductive plate 3, and a Hall voltage is generated at this time. After the Hall voltage signal intermittently generated by the Hall element is amplified and shaped by the Hall integrated circuit, the voltage pulse signal is transmitted to the ECU. Every time the external signal wheel rotates 1 generates 18 pulse signals (called 18x signal), 1 pulse period is equivalent to the crankshaft rotating for 20 degrees, and the ECU will rotate 1 pulse. The function of this signal is equivalent to the function of 1 signal generated by photoelectric crankshaft position sensor. The inner signal wheel generates three voltage pulse signals (called 3X signals) with different widths every 1 revolution, the pulse period is 120 crank angle, and the rising edges of the pulses are respectively generated at 75 degrees before the top dead center of 1, 4, 3, 6, 2 and 5 cylinders, which are used as reference signals for ECU to judge cylinders and calculate ignition time, which is equivalent to the aforementioned.
(2) Hall crankshaft position sensor with trigger gear teeth.
The Hall crankshaft position sensor of Chrysler Company is installed on the flywheel housing, and adopts the trigger gear tooth structure. At the same time, a synchronous signal generator is set in the distributor to assist the crankshaft position sensor to identify the cylinder number. The Hall crankshaft position sensor of Beijing Cherokee has eight slots on the flywheel of a 2.5L four-cylinder engine, which are divided into two groups. Every four slots are a group, and the two groups are separated by 180, and every two adjacent slots in each group are separated by 20. There are 12 slots on the flywheel of a 4. OL six-cylinder engine. The four tanks are divided into three groups, each group is separated by 120, and two adjacent tanks are also separated by 20.
When the cogging of the flywheel passes through the signal generator of the sensor, the Hall sensor outputs a high potential (5V); When the metal between the cogging of the flywheel is in line with the sensor, the sensor outputs a low potential (0.3V). Therefore, whenever 1 flywheel cogging passes through the sensor, the sensor generates 1 high and low potential pulse signals. When each group of slots on the flywheel passes through the sensor, the sensor will generate four pulse signals. Four-cylinder engine produces two groups of pulse signals every 1 revolution, and six-cylinder engine produces three groups of pulse signals every 1 revolution. Engine ECU can use each set of signals provided by sensors to determine the position of the double-cylinder piston. For example, on a four-cylinder engine, a set of signals can be used to know that piston 1 and piston 4 are close to top dead center; Using another set of signals, it can be known that piston 2 and piston 3 are close to top dead center. Therefore, using the crankshaft position sensor, ECU can know that the pistons of two cylinders are approaching the top dead center. Because the pulse falling edge of the fourth slot corresponds to 4 before the piston top dead center (TDC), the ECU can easily determine the working position before the piston top dead center according to the pulse condition. In addition, the ECU can also calculate the engine speed according to the elapsed time between pulses. The detection method of Hall crankshaft position sensor has a * * similarity, that is, it is judged mainly by measuring whether it outputs electric pulse signals. Here, taking Beijing Cherokee Hall crankshaft position sensor as an example, the detection method is explained.
The crankshaft position sensor is connected with the ECU through three wires. One of them is the power line that ECU applies voltage to the sensor, and the voltage input to the sensor is 8V; The other is the output signal line of the sensor. When the flywheel cogging passes through the sensor, the Hall sensor outputs a pulse signal with a high potential of 5V and a low potential of 0.3V: The third is the ground wire leading to the sensor.
(1) Sensor power supply and voltage test
Turn the ignition switch to the "on" position, measure the voltage of terminal 7 on the ECU side with a multimeter, and measure the voltage of terminal "A" of the sensor wire connector at 8V, otherwise there will be power supply, disconnection or poor contact of the connector.
(2) Detection of voltage between terminals
Use the voltage range of multimeter to test the three terminals of sensor ABC. When the ignition switch is turned on, the voltage between terminals A and C is about 8V. When the engine rotates, the voltage between B-C terminals changes between 0.3-5v, and the digital display shows pulse changes, with the highest voltage of 5v and the lowest voltage of 0.3V. If the above results are not met, replace the crankshaft position sensor.
(3) Resistance detection
Turn the ignition switch to the "OFF" position, unplug the wire connector of the crankshaft position sensor, and connect it between the A-B or A-C terminals on the sensor side with a multimeter Ω. At this time, the multimeter shows a reading of ∞ (open circuit). If resistance is displayed, replace the crankshaft position sensor.
The test method of trigger vane Hall sensor of General Motors is similar to the above, except that it has four terminals, and the top dead center signal output terminal (triggered by internal signal wheel) and the ground terminal are displayed by pulse voltage.