Detailed explanation of the role and classification of automobile wheel speed sensors

Author    |    jinzhou_admin    |    May 28, 2021

NISSAN 85-6144 47910-AV700

Nowadays, in the fast-developing society, convenient transportation is becoming more and more important. On this basis, automobiles have become especially common and important, becoming a new type of transportation tool. However, with the popularization of automobiles, it will also bring certain negative effects. For example, more and more traffic accidents occur frequently, which also brings tremendous pressure to society and people. Under this circumstance, with the development of sensor technology, the existence of various automotive sensors that follow cannot be ignored, and wheel speed sensors are very important and critical components relative to modern cars. Today, the editor of Sensor Expert Network will take you to understand the main classification and important functions of automobile wheel speed sensors.

Wheel speed sensor

NISSAN 85-6147 47900-AV710

Without the important help of wheel speed sensors, drivers everywhere will tend to have multiple speeding tickets. Wheel speed sensors, also called ABS sensors, are installed on the wheels of the driving tires and are responsible for monitoring various vehicle functions, such as traction control, anti-lock braking system, and vehicle speed. Due to this fact, when the wheel speed sensor goes bad or fails, it usually affects the operation of these other vehicle functions and displays certain warning signals that any driver can immediately notice while driving.

The wheel speed sensor is different from the speed sensor installed in the vehicle gearbox. Its job is to record the actual wheel speed and report this data to the vehicle ECU, which controls all electronic functions on the car, truck or SUV. As with any electronic device, the best way to determine the operation of a wheel speed sensor is to use a voltmeter to measure the voltage output. Since most car owners cannot use this tool, they must rely on warning signs, which may indicate that the component has begun to wear or has been damaged and needs to be replaced as soon as possible.

Generally speaking, all rotational speed sensors can be used as car wheel speed sensors, but considering the actual factors such as the working environment of the wheels and the size of the space, the commonly used wheel speed sensors mainly include: magnetoelectric wheel speed sensors, Hall wheel speed sensors sensor.

The magneto-electric wheel speed sensor is designed using the principle of electromagnetic induction. It has the characteristics of simple structure, low cost, and no fear of mud. It is widely used in the ABS anti-lock braking system of modern cars. The magnetoelectric wheel speed sensor is generally composed of a magnetic induction sensor head and a ring gear, and the sensor head is composed of a permanent magnet, a pole shaft, an induction coil, and so on. The ring gear is a moving part, which is generally installed on the hub or on the axle to rotate with the wheel. The wheel speed sensor head is a stationary part, and there is a certain gap between the magnetic pole of the sensor head and the end face of the ring gear. As shown below.

Magnetoelectric wheel speed sensor installation diagram

NISSAN 85-6070 47900-1MA0A

The magnetoelectric wheel speed sensor is composed of a permanent magnetic core and a coil. The lines of magnetic force emerge from one pole of the core, pass through the ring gear and air, and return to the other pole of the core. Since the coil of the sensor is wound on the magnetic core, these magnetic lines of force will also pass through the coil. When the wheel rotates, the ring gear (rotor) that is synchronized with the wheel rotates with it, and the teeth and gaps on the ring gear quickly pass the magnetic field of the sensor in turn. As a result, the magnetic resistance of the magnetic circuit is changed, which causes the induced electric potential in the coil to occur. Change to produce a potential pulse of a certain amplitude and frequency. The pulse frequency, that is, the number of pulses generated per second, reflects the speed of the wheel rotation, as shown in the figure below.

Hall type wheel speed sensor structure

NISSAN 85-6104 D7910-ZR00B

The Hall-type wheel speed sensor is made using the principle of Hall effect. The Hall-type wheel speed sensor has also been widely used in automobiles, and has the following characteristics: the output signal voltage amplitude value is not affected by the rotation speed; the frequency response is high; Strong anti-electromagnetic wave interference ability.

The Hall-type wheel speed sensor is composed of a sensor head and a ring gear. The sensor head is composed of permanent magnets, Hall elements and electronic circuits. As shown below. The Hall-type wheel speed sensor uses the principle of the Hall effect, that is, a control current is passed through both ends of the semiconductor sheet, and a magnetic field with a magnetic field strength of B is applied in the vertical direction of the sheet, and a size will be generated at the other ends of the sheet. The electric potential proportional to the product of the control current and the magnetic induction intensity B is the Hall electric potential.

The above is the introduction of the sensor expert network to the wheel speed sensor. All in all, for modern cars, wheel speed information is indispensable. Vehicle dynamic control system (VDC), automotive electronic stability program (ESP), anti-lock braking System (ABS), automatic transmission control system, etc. all need wheel speed information, so the wheel speed sensor is one of the most critical sensors in modern cars.