Drives and Controls Magazine
Seal-shaped bearing sensor adapts to the application
Published:  08 May, 2017

The German bearings-maker Schaeffler – which has been offering sensor-equipped bearings and guidance systems for several years ­– stated at the recent Hannover Fair that its aim is to transform conventional mechanical products and to integrate them into the digital world. Its latest development is a 7mm-thick ring-shaped device that can contain a choice of sensing elements to suit an application, and occupies a similar space to the rotary shaft seal of a bearing. The housing is attached to a bearing’s outer ring, and the sensor ring to the inner ring.

Initially, the system, called VarioSense, will be able to measure parameters such as:

•  temperatures from –40 to +125°C;

•  speeds up to 17,000 rpm, including detecting the direction of rotation;

•  the number of revolutions, or position, with 56–96 impulses/revolutions (depending on the size);

•  vibration signals; and

•  maximum radial shaft displacements to a resolution of 1µm.

Schaeffler says that the sensors can be used to control drives, calculate the operating lives of components such as bearings and gears, and to monitor processes.

Schaeffler’s VarioSense bearing monitoring device occupies the same space as a seal

The shaft displacement measurements can be used to determine the radial force on a bearing. If the powertrain is already present in the Schaeffler Cloud as an algorithm in its Bearinx calculation software, the forces and displacements on the other bearings and machine elements – such as gears – can also be determined indirectly, as can the torque. This means that the most important values for monitoring parameters in machines are known. For example, overloads can be recorded, and torque can be limited and drives switched off, if necessary.

The first bearings to support the VarioSense system are the widely-used 6205 to 6210 ball-bearings. They are supplied with an interface box for power supply, signal processing and networking, and can operate on voltages from 4.5–30V.

Schaeffler is working on various customer projects involving the VarioSense technology. A monitored machine does not always need to be networked to a complete production line or to a supervisory controller. According to Schaeffler, many potential users see benefits in being able to close control loops using values measured locally, or switching off a machine when overloading occurs or when temperatures are too high.

Schaeffler is also working on various internal projects, such as using the sensing technology in the electric motors used to drive forklifts or electric scooters. In such applications, it is important to have a robust, integrated sensor that is protected from environmental influences. The most important element of recording the speed in such cases is to close local control loops.

The company is also using the technology to record loads in motor-transmission couplings. It says that this can be achieved faster and more directly by using measuring points in the bearing, rather than by monitoring the motor current, and is not affected by any elasticity in the powertrain. In such applications, remaining operating lives can be calculated and transmitted via a cloud connection.