Wireless Active ABS Sensor with Zero Speed Detection Capability

NTN Corporation has developed a wireless active ABS sensor that can detect rotation speed and direction with true zero speed detection capability.

Currently, automotive wheel speed sensors are used for anti-lock brakes and vehicle stability and traction control systems on low-friction road surfaces. For these applications, active ABS sensors with zero speed detection capability are typically used, but these sensors generally have expensive cable wiring harnesses and connectors.

Today's active ABS sensors also require 1) screw tightening of the sensor to the suspension knuckle during installation on the vehicle assembly line, 2) routing of the sensor cable from the sensor installation to the wiring harness connector, and 3) rugged covering on the sensor cables to protect them from damage by road debris and exposure to extreme ambient conditions.

In order to solve these wiring problems, NTN had previously developed a wireless passive ABS sensor that uses the electrical power generating characteristics to produce a self-energizing speed sensor. However, with these sensors, true zero speed detection could not be provided because of the inherent low power at low rotational speeds. In addition, this sensor type did not have a rotation direction detection function, which is necessary for "launch assist control" when starting up a manual transmission vehicle on an inclined surface.

NTN's new wireless active ABS sensor detects the rotation speed with an active magnetic sensor and multi-pole magnet housed in the hub bearing and supplies the electrical power for wireless transmission of this rotation signal through a wireless power supply located inside the vehicle body. This makes it possible to measure rotation speed at zero velocity wirelessly and alleviates the other problems encountered with the current wired active ABS sensors. Also, because this new sensor has two separate sensing elements installed with a preset phase difference, forward/reverse rotation direction can be determined, allowing this new sensor to be used in launch assist control systems to prevent a manual transmission car from rolling backwards when starting up on a hill, and other such applications.

Features

1. Zero speed rotating velocity measurement capability
2. Zero speed forward/reverse direction detection
3. Wireless advantages

   · No sensor cables, connectors, or wiring harness installation

   · Improved reliability because sensor cables cannot be damaged by debris or exposure to extreme ambient conditions

4. Compact package size
   The sensor is positioned within the hub bearing, with only the transmitter and antenna on the outside of the overall package, so the overall unit is more compact

Application

Automotive wheel speed sensors

NTN's GEN 4 hub bearing with wireless active ABS sensor