Crankshaft position sensor: Crankshaft position sensor is one of the most important sensors in engine electronic control system. It provides ignition time (ignition advance angle) and signals to confirm crankshaft position, and is used to detect piston top dead center, crankshaft angle and engine speed. The structure of crankshaft position sensor varies with different models, which can be divided into three categories: magnetic pulse type, photoelectric type and Hall type. Usually installed at the front end of crankshaft, camshaft, flywheel or distributor. 1. Detection of Magnetic Pulse Crankshaft Position Sensor 1, Structure and Working Principle of Magnetic Pulse Crankshaft Position Sensor (1) The crankshaft position sensor is installed behind the pulley at the front end of the crankshaft, and there is a thin toothed disc (called signal disc) at the rear end of the pulley, which is installed on the crankshaft together with the crankshaft pulley and rotates with the crankshaft. On the outer edge of the signal board, there are teeth every four times along the circumference. * * * There are 90 teeth, and 1 flange is arranged every 120, ***3. The sensor box installed at the edge of the signal panel is a signal generator that generates electrical signals. There are three magnetic heads wound with induction coils on the permanent magnet in the signal generator, of which magnetic head ② generates a signal of 120, and magnetic head ① and magnetic head ③ * * * generate a crank angle signal of 1. The magnetic head ② faces the 120 flange of the signal panel, and the magnetic head ① and the magnetic head ③ face the gear ring of the signal panel, and are installed at a crank angle apart. The signal generator has a signal amplification and shaping circuit inside and a four-hole connector outside. Hole "1" is the signal output line of 120, hole "2" is the power line of the signal amplification and shaping circuit, hole "3" is the signal output line of 1, and hole "4" is the ground line. The signal generated by the crankshaft position sensor is transmitted to the ECU through this connector. When the engine rotates, the teeth and flanges of the signal board make the magnetic field passing through the induction coil change, thus generating alternating electromotive force in the induction coil, which becomes a pulse signal after filtering and shaping. Every engine revolution, three 120 pulse signals are generated on magnetic head ②, and 90 pulse signals are generated on magnetic heads ① and ③ respectively (alternately). Since the magnetic head ① and the magnetic head ③ are installed at crank angles separated by 3 degrees, and they generate a pulse signal every 4 degrees, the phase difference of the pulse signals generated by the magnetic head ① and the magnetic head ③ is exactly 90 degrees. These two pulse signals are sent to the signal amplification and shaping circuit for synthesis, and the signal of crank angle 1 is generated. The magnetic head ② generating 120 signal is installed at 70 before TDC, so its signal can also be called 70 before TDC, that is, when the engine is running, the magnetic head ② generates a pulse signal at 70 before TDC of each cylinder. (2) Toyota's magnetic pulse crankshaft position sensor The Toyota TCCS system uses the magnetic pulse crankshaft position sensor installed in the distributor. The sensor is divided into an upper part and a lower part. The upper part generates G signal and the lower part generates Ne signal. When the rotor with gear teeth rotates, the magnetic flux in the induction coil of the signal generator changes, thus generating alternating induced electromotive force in the induction coil, which is then amplified and sent to the ECU. Ne signal is a signal for detecting crankshaft angle and engine speed, which is equivalent to 1 signal of crankshaft position sensor with daily magnetic pulse. This signal is generated by a rotor (No.2 timing rotor) with 24 equally spaced teeth fixed in the lower half and an induction coil fixed on the opposite side. When the rotor rotates, the air gap between the gear teeth and the flange (magnetic head) of the induction coil changes, resulting in changes in the magnetic field and induced electromotive force passing through the induction coil. When the gear teeth are close to and away from the magnetic head, there will be changes that increase or decrease the magnetic flux. Therefore, when each gear tooth passes through the magnetic head, a complete AC voltage signal will be generated in the induction coil. N0.2 There are 24 teeth on the timing rotor, so when the rotor rotates 1 turn, that is, the crankshaft rotates 720 degrees, the induction coil generates 24 AC voltage signals. As shown in fig. 6(b), the pulse of one cycle of the ne signal is equivalent to 30 crank angle (720 ÷ 24 = 30). More accurate angle detection is to use the time of 30 degrees, which is divided into 30 equal parts by ECU, that is, to generate a signal of 1 crankshaft angle. Similarly, the engine speed is measured by ECU according to the elapsed time of two pulses (60 crank angle) of ne signal. G signal is used to judge the cylinder and detect the top dead center position of the piston, which is equivalent to the 120 signal of the crankshaft position sensor with daily magnetic pulse. G signal is generated by the flange runner (No.1 timing rotor) located above the Ne generator and its two relatively symmetrical induction coils (G 1 induction coil and G2 induction coil). The principle of signal generation is the same as that of Ne signal. The G signal is also used as a reference signal when calculating the crank angle. G 1 and G2 signals detect the top dead center of the sixth cylinder and 1 cylinder respectively. Because of the positions of G 1 and G2 signal generators, when G 1 and G2 signals are generated, the piston actually does not just reach the top dead center (BTDC), but is at the position of 10 before the top dead center. 2. Detection of magnetic pulse crankshaft position sensor Taking the magnetic pulse crankshaft position sensor used in the electronic control system of 2JZ-GE engine of Crown 3.0 car as an example, the detection method is explained. (1) Check the resistance of the crankshaft position sensor. Turn off the ignition switch, unplug the wire connector of the crankshaft position sensor, and measure the resistance between the terminals of the crankshaft position sensor with a multimeter. If the resistance value is not within the specified range, the crankshaft position sensor must be replaced. Resistance value of crankshaft position sensor terminal Conditional resistance value (ωω)G 1-G-G- cold 125-200 heat 160-235 G2-G- cold 125-200 heat160. (2) Detection of the output signal of the crankshaft position sensor Unplug the wire connector of the crankshaft position sensor. When the engine is rotating, use the voltage range of the multimeter to detect whether there is a pulse voltage signal output between the G 1-G-, G2-G- and Ne-G- terminals of the crankshaft position sensor. If there is no pulse voltage signal output, the crankshaft position sensor must be replaced. (3) Clearance inspection between induction coil and timing rotor Measure the air gap between the timing rotor and the protruding part of induction coil with a thickness gauge, and the gap should be 0.2-0.4 mm. If the gap does not meet the requirements, the distributor housing assembly must be replaced. Two. The structure and work of photoelectric crankshaft position sensor 1 and photoelectric crankshaft position sensor (1) The structure and work of Nissan photoelectric crankshaft position sensor are installed in the distributor, which consists of a signal generator and a signal disk with notches and light holes. The signal panel is installed on the distributor shaft, with a 360-degree gap around it, generating a 1 (crankshaft angle) signal; There are six light holes (at intervals of 60) slightly inside the periphery to generate 120 signal, and one wide light hole generates 120 signal corresponding to the cylinder 1 TDC. The signal generator is fixedly installed on the shell of the distributor and mainly consists of two light-emitting diodes, two photosensitive diodes and an electronic circuit. The two light emitting diodes are respectively opposite to the photodiode, and the light emitting diodes take the photodiode as the irradiation target. The signal panel is located between the light emitting diode and the photosensitive diode. When the signal panel runs with the crankshaft of the engine, because there are light holes on the signal panel, the light transmission and shading change alternately, so that the signal generator outputs pulse signals representing the position and rotation angle of the crankshaft. When the light beam of the light emitting diode irradiates on the photosensitive diode, the photosensitive diode is photosensitive and turned on; When the light beam of the LED is blocked, the photodiode is turned off. The pulse voltage signal output by the signal generator is sent to the electronic circuit for amplification and shaping, and the crank angle signal of 1 and the crank angle signal of 120 are sent to the electronic control unit. Due to the installation position of the signal generator, the 120 signal is output 70 before the piston top dead center. When the engine crankshaft rotates once, the distributor shaft rotates once 1, 1. The signal generator outputs 360 pulses. In each pulse period, the high potential corresponds to 1, the low potential corresponds to 1, and * * stands for 720 crank angle. At the same time, the 120 signal generator * * * generates six pulse signals. (2) Modern Sonata The structure and work of the photoelectric crankshaft position sensor for automobiles Modern Sonata, the working principle of the photoelectric crankshaft position sensor for automobiles is similar to that of Nissan, but the structure of its signal panel is slightly different. For the automobile with distributor, the sensor assembly is installed in the shell of distributor; For cars without distributor, the sensor assembly is installed at the left end of the camshaft (looking back from the front of the car). There are four holes in the outer ring of the signal panel, which are used to sense the crank angle and convert it into voltage pulse signals. The electronic control unit calculates the engine speed according to the signal and controls the gasoline injection timing and ignition timing. In the inner ring of the signal panel, there is a hole for sensing 1 cylinder compression top dead center (in some Sonata cars, there are two holes for sensing 1 cylinder compression top dead center and 4-cylinder compression top dead center), which is converted into a voltage pulse signal and input to the electronic control unit, and the electronic control unit calculates the gasoline injection sequence according to this signal. There are two light emitting diodes and two light sensitive diodes in it. When the light-emitting diode illuminates one of the light-transmitting holes of the signal panel, the light will illuminate the photosensitive diode to make the circuit conductive. 2. Detection of photoelectric crankshaft position sensor (1) When checking the wiring harness of the crankshaft position sensor, disconnect the wire connector of the crankshaft position sensor, turn the ignition switch to the "on" position, and measure the voltage between the 4# terminal and the ground on the wiring harness side with a multimeter. The voltage between the 2# terminal and the 3# terminal on the wiring harness side should be 4.8-5.2V Use a multimeter to detect the resistance of the photoelectric crankshaft. When starting the engine, the voltage should be 0.2-1 .2v. During the idling operation after the engine is started, the voltage of terminal 2 and terminal1should be1.8-2.5v. Use the voltage range of multimeter to detect. Otherwise, replace the crankshaft position sensor. Third, the detection of Hall crankshaft position sensor uses the principle of Hall effect to generate voltage pulse signal corresponding to crankshaft angle. It uses trigger blades or gear teeth to change the magnetic field intensity passing through the Hall element, so that the Hall element generates a pulsed Hall voltage signal, which is amplified and shaped as the output signal of the crankshaft position sensor. Hall Crankshaft Position Sensor (1) Hall Crankshaft Position Sensor with Trigger Blade The Hall Crankshaft Position Sensor of General Motors of the United States is installed at the front end of the crankshaft and adopts the structure of trigger blade. 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 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 Tooth Chrysler's Hall Crankshaft Position Sensor is installed on the flywheel housing and adopts the structure of trigger tooth. 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 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. 2. Detection of Hall Crankshaft Position Sensor The detection method of Hall Crankshaft Position Sensor has a * * * similarity, that is, it is mainly judged 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) Test of sensor power supply and voltage: Turn the ignition switch to the "on" position, measure the voltage of terminal 7 on the ECU side with a multimeter voltage range, and measure the voltage of terminal "A" of the sensor wire connector, otherwise it is power supply, disconnection or poor contact of the connector. (2) Use the voltage range of multimeter to test the three terminals of sensor ABC to detect the voltage between terminals. 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) Turn the resistance detection ignition switch to the "OFF" position, unplug the lead 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.