1. Detection of magnetic pulse crankshaft position sensor
1, structure and working principle of magnetic pulse crankshaft position sensor
(1) Crankshaft Position Sensor with Daily Magnetic Pulse
The crankshaft position sensor is installed behind the pulley at the front end of the crankshaft, as shown in figure 1. The rear end of the pulley is equipped with a thin circular toothed disc with fine teeth (used to generate signals, called signal disc), 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 flange of the signal board change the magnetic field passing through the induction coil, thus generating alternating electromotive force in the induction coil, which is filtered and shaped into a pulse signal (as shown in Figure 2). 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 (as shown in Figure 3).
The magnetic head ② generating 120 signal is installed at 70 before the top dead center (Figure 4), so its signal can also be called 70 before the top dead center, that is, during the engine operation, the magnetic head ② generates a pulse signal at 70 before the top dead center of each cylinder.
(2) Toyota magnetic pulse crankshaft position sensor.
The magnetic pulse crankshaft position sensor used in Toyota TCCS system is installed in the distributor, and its structure is shown in Figure 5. The sensor is divided into upper and lower parts. 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. The signal is generated by a rotor (No.2 timing rotor) with 24 teeth at equal intervals, which are fixed in the lower half and the induction coil is fixed on the opposite side (as shown in Figure 6(a)).
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). Its structure is shown in Figure 7. 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. Fig. 8 shows the relationship between crank position sensor G 1, G2 and Ne signals and crank angle.