What is the principle of wheel speed sensor?
Wheel speed sensor and the general principle of the same AC motor. Permanent magnets produce a certain intensity of the magnetic field, the ring gear in the magnetic field rotation, the tooth ring tooth tip and the gap between the electrode to a certain rate of change, so that the ring and the electrode composition of the magnetic circuit in the magnetic resistance Variety. As a result, the magnetic flux is periodically increased or decreased, and the induced voltage is proportional to the increase or decrease of the magnetic flux at both ends of the coil at both ends of the coil. The magnetic field strength into voltage, magnetoresistance into resistance, magnetic flux into the current, analogy Ohm's law its working principle is easy to understand. Therefore, the induced voltage is proportional to the wheel speed.
The sensor leads to two wires to the electronic control unit, which must be shielded. Wheel speed sensor or its line If there is a fault, ABS electronic control unit will automatically record the fault, ignite the fault indicator, so that ordinary brake system to work.
The operation of the wheel speed sensor is shown in Figure 1-7. The sensor head and the ring gear next to the fixed, when the ring gear with the wheel rotation, the permanent magnet on the electromagnetic induction coil to produce an AC signal (this is because the ring gear on the tooth and the valley through the magnetic field caused by strong Weak change of the fault), the frequency of the AC signal is proportional to the wheel speed, and the amplitude of the AC signal varies with the wheel speed (DST ABS (VI) is 0.1V at the lowest speed and 9V at the maximum). The ABS electronic control unit determines the speed of the wheel by identifying the frequency of the AC signal sent by the sensor. If the electronic control unit discovers that the wheel's deceleration is rapidly increasing and the slip rate S reaches 20%, it immediately sends a command to the hydraulic regulator, Reduce or stop the wheel's braking force, so as not to wheel lock.
