For modern cars, wheel speed information is indispensable. Automotive dynamic control systems (VDC), automotive electronic stability programs (ESP), anti-lock braking systems (ABS), automatic transmission control systems, etc. all require wheel speed information. Speed information. Therefore, the wheel speed sensor is one of the most critical sensors in modern cars.
Generally speaking, all speed sensors can be used as wheel speed sensors, but considering the actual factors such as the working environment of the wheel and the size of the space, the commonly used wheel speed sensors mainly include: magnetoelectric wheel speed sensor, Hall-type wheel speed sensor .
The magnetoelectric wheel speed sensor is designed using the principle of electromagnetic induction, and its main components are shown in the figure below.
It has the characteristics of simple structure, low cost, not afraid of mud and dirt, and is widely used in the ABS anti-lock braking system of modern cars.
(1) The frequency response is not high. When the vehicle speed is too high, the frequency response of the sensor cannot keep up, and it is easy to produce false signals;
(2) Poor anti-electromagnetic wave interference ability, especially when the output signal amplitude value is small.
The Hall-type wheel speed sensor is made using the principle of Hall effect, as shown in the figure below. Hall-type wheel speed sensors have also been widely used in automobiles.
(1) The amplitude of the output signal voltage is not affected by the speed;
(2) High frequency response;
(3) Strong anti-electromagnetic wave interference ability.
The wheel speed sensor is composed of permanent magnets, magnetic poles, coils and ring gears. (See the figure below) When the ring gear 5 rotates in a magnetic field, the gap between the tooth tip of the ring gear and the electrode changes at a certain speed, which changes the magnetic resistance in the magnetic circuit.
As a result, the magnetic flux is increased and decreased periodically, an induced voltage proportional to the increase and decrease speed of the magnetic flux is generated at both ends of the coil 1, and the AC voltage signal is sent to the electronic controller.