NTN-SNR wheel speed sensors
CREATOR of the instrumented wheel bearing, NTN-SNR launched on the market a new technology: ASB® (Active Sensor Bearing) allowing it to be established as a WORLDWIDE STANDARD.
That technology makes it possible to replace so-called passive technology with “active” technology, comprising an active sensor and a seal with an integrated magnetic encoder. The latter features a series of very precise north and south poles that send a digital signal corresponding to the wheel speed. This solution offers a number of benefits, including:
– Signal detection at low speed (down to zero)
– Integration of the magnetic ring with the bearing seal: system miniaturisation
– Reduced number of parts: simplified wheel installation
– More precise data acquisition
– Standardisation of components
Today, more than 90% of vehicles on the road are equipped with wheel speed sensors. The sensor measures the wheel speed on the magnetic encoder seal or on the toothed wheel located on the bearing. The information is then transmitted to many other systems which control vehicle dynamics along with a wide range of ancillary functions such as: ASB, ESP, ASR, speed, navigation, hill holder…. Loss of the ASB® signal can have serious consequences: The ABS fault indicator will light up on the dashboard. The ABS system is no longer working correctly, no longer prevents the wheels from locking up and no longer ensures vehicle stability during braking.
The main advantage of NTN-SNR ASB® technology is that it delivers a signal with constant amplitude, even at low speed or zero speed. This enables greater precision in the use of the wheel speed signal and improves the function of all systems associated with that signal.
There are three different types of active sensors:
– Active Hall effect sensor: The sensor consists of a semiconductor coupled to an electronic circuit. As a result, it produces an alternating current. The electronic part of the sensor converts the analogue signal from the current into a digital signal.
– Active Hall effect sensor in combination with a magnetic encoder seal on the wheel bearing: the magnetic field is generated by the north and south poles of the magnetic encoder seal as they pass in front of the sensor. The toothed wheel is replaced by a magnetic encoder.
– Active magneto-resistive sensors: This technology makes it possible to detect the signal in complex structures where the sensor is located at a greater distance from the encoder seal.
An ASB® signal malfunction may supply incorrect information to the system computer causing (ECU):
– False triggering of the ABS system when the brakes are applied
– Incorrect calculation of individual wheel speeds by the computer: ESP system may no longer control the vehicles direction
– Incorrect speed display: may cause a significant risk of unintended and dangerous exceeding of the speed limit.
It was therefore logical that we should extend our offer by providing our customers with the component that linked our core business –the wheel bearings- with our expertise- the ASB® technology – the sensor itself!
Pierre Touvier / Sales Area Manager
Claire Bianchin / Communication Manager
Géraldine Bourgeay / Marketing Assistant