Measuring the loads and displacements which occur in a bearing is a reliable way to assess both processes and machine condition. The more precise the measurement, and the greater the number of measured values, the sharper the digital image. It is against this background that Schaeffler is presenting configurable FAG VarioSense bearings at the Hannover Messe 2017. They allow a specific combination of measured values to be recorded to suit the application.
For this task, Schaeffler’s mechatronics developers have integrated several sensor elements into a ring-shaped housing which has a section height of only 7 mm. The sensor cluster, therefore, occupies approximately the same amount of space as a rotary shaft seal. To keep handling simple, the sensor housing is fixed to the outer ring and the sensor ring is fixed to the bearing inner ring. Therefore, it forms a very compact unit.
Combination of sensor elements
With this sensor cluster, the number and combination of measured values can be individually set for each application. The range of values which can be measured is currently:
Temperature from -40 to +125°C,
Speed up to 17,000 rpm including detection of the rotation direction
Number of revolutions or position with 56-96 impulses/revolutions (dependent on size)
Vibration signals for long-term trending and
Maximum radial shaft displacement to a resolution of 1 µm.
Measuring the radial shaft displacement in the bearing lets the radial bearing force on the sensor bearing to be determined through interactions recognized by the computer. If the specific powertrain is already present in the Schaeffler Cloud as an algorithm in the Bearinx calculation software, the forces and displacements at the other bearings and machine elements, such as the gears, can also be determined indirectly from these data, as can the torque. This means that the most important values for monitoring the process parameters in machines and equipment are known which provides significant added benefits for the operator. For example, overloading can be easily recorded and it is also possible to limit torques as well as switch off the drive if necessary.
In summary, the sensor component of the VarioSense bearings can be used as a primary function, i.e. controlling drives, calculating residual operating life of machine elements (rolling bearings, gears etc.), as well as for monitoring the process. The sensor housing presented also allows other measured values to be integrated in future applications for customer-specific solutions.
The first range of VarioSense bearings is available for the extremely commonly used 6205 to 6210 series of ball bearings. The VarioSense bearings are supplied with an interface box for power supply, signal processing and networking. VarioSense bearings can be used in a wide range of voltages from 4.5 V to 30 V.
The current number of project requests from customers is proof of the universal range of applications for these configurable sensor bearings. From white goods, pumps and electric motors through drives for agricultural and construction machinery, electric vehicles, fork lift trucks and other machinery to applications in wind turbines, conveying technology and elevator technology — the range of sectors is almost limitless. This shows that it is not always necessary for the machine to be fully networked, for example to the whole production line, or for the machine to be networked to a supervisory control level. Many manufacturers can see an additional benefit or a competitive advantage in closing control loops using values measured on a locally operated machine, such as positioning control or switching off the unit when overloading occurs or when the temperature reaches an unacceptable level.
Schaeffler is pursuing specific projects, for example, electric motors in industrial mobility, such as fork lift trucks, or in electric scooters. In these applications, it is particularly important to have a robust sensor integrated into the bearing which is also protected from environmental influences. The most important element of recording the speed in this instance is closing local control loops. Projects are running in motor-transmission couplings to record the load. This can be recorded more quickly and more directly through measuring points in the bearing than by using the motor current and is not affected by any elasticity in the powertrain. In these applications, the load data classification and the residual operating life can be calculated and output via a cloud connection.