SENSOR ROLLER AND BEARING ASSEMBLY

Technical Field

The invention relates to a sensor roller and to a bearing assembly including such a sensor roller. Technical Background

It is known to provide bearings with various sensors for load sensing and measuring temperature, rotating speed, noise etc.. In some cases, sensors are arranged together with wireless transmitters inside of rollers and need to be supplied with energy. One solution for this problem is to use a battery. However, the battery lifetime has turned out to fall short of the bearing lifetime in important fields of application and exchanging the batteries is inconvenient.

The document EP 0637 734 A1 discloses a device for load measurement in roller bearings whereby the measurement is carried out by means of sensors arranged to measure forces applied on the bearing. The sensors communicate with means for recording, processing and evaluation of signals emitted from the sensors, which are representative of the bearing load. At least one roller body per roller body row is provided with a bore in which is provided at least one sensor, as well as means for amplification and transmission of signals emitted from said sensor to a receiver. The receiver is provided at the nonrotating bearing ring of the bearing. The signals received by the receiver are forwarded to further external means for signal processing. The energy supply of the transmission and amplification means is achieved by means of a small coil mounted in connection to the amplifier/transmitter in the bore of the roller and the end thereof protrudes outside the end of the roller. This coil is arranged in the sensor roller so as to communicate with a large, stationary coil provided at the stationary bearing ring. The stationary coil provides the coil arranged in the roller with energy, and the coil arranged in the bore sends continuous load data, in the form of strain values from the sensors.

The solution of EP 0637 734 A1 has drawbacks in that the amount of energy which can be supplied to the small coil is limited, in particular in the case of low rotation speeds of the bearing. The document DE69828236 T2 teaches a bearing assembly with a roller having a bore, wherein a generator and a gearbox is provided inside of the bore. The gearbox is connected to a cage of the bearing with an elastic coupling member.

The solution proposed in the DE69828236 T2 has drawbacks in terms of robustness and lifetime of the elastic coupling member. Further, the elastic connection does not allow for overlooking or slippage protecting the internal parts of the roller from damages in the case of shocks or excessively high rotation speeds and the elastic properties of the elastic coupling member are sensitive to temperature changes and subject to ageing.

Summary of the Invention

It is an object of the invention to provide a sensor roller with integrated generator assembly with reduced maintenance costs and long lifetime.

The invention starts from a sensor roller for a bearing including an inner ring, an outer ring and a plurality of rollers including said sensor roller is arranged in a cage between the inner ring and the outer ring, wherein the sensor roller is provided with a bore accommodating a sensor unit and at least a part of a generator assembly and wherein said part of the generator assembly is configured to interact with said cage in order to generate energy out of a relative rotation between the cage and the roller. It is proposed that the interaction is a magnetic interaction. The use of a magnetic coupling instead of an elastic coupling element enables a practically wear-free operation and long lifetime. The magnetic properties are less susceptible to external influences than elastic properties of an elastic coupling member. Further, the magnetic interaction may be easily generated with permanent magnets and may contribute to the magnetic flux circuits used by the generator.

The invention is applicable to large-size roller bearings such as bearings for wind turbines which need to be monitored. Limitations are imposed by the maximum degree of miniaturization available for the generator assembly to be fitted into the bore of the roller and the amount of power that is to be generated at a certain rotational speed. The bearings may be single- or multiple-row roller bearings and may be equipped with one or more sensor rollers per row.

The sensor unit may comprise strain sensors, temperature sensors, vibration sensors or other sensors desired.

Further, it is proposed that said part of a generator assembly includes a generator shaft provided with a magnet at its shaft end, wherein said magnet is configured to interact with a further magnet provided on the cage. This embodiment enables the use of an off-the shelf generator, which only has to be equipped with a preferably disk-shaped permanent magnet at the end of its shaft connected to a rotor of the generator, whereas the body of the generator including the stator can be fitted into the bore and fixed therein in a non-rotating manner.

Preferably, the generator assembly comprises a brushless DC generator and an AC-DC converter and energy storage circuit. The AC-DC converter and energy storage module can be a simple rectifier with voltage output regulator (buck/boost), or a voltage multiplier circuit and a voltage regulator or battery charger circuit. The person skilled in the art will select the type of storage cell dependent on the intended usage profile in combination with the roller speed profile. E.g. for bearing defects detection, it only makes sense to measure when the bearing is moving. For static measurements: temperature, strain, angle, etc., it is necessary to rely on the energy storage capacity of the module.

The type of energy storage means depends on the usage (measurement and transmission) profile in combination with the rotational speed profile. Strategies can be developed to only measure and transmit when there is enough power from the generator and that the data is backed up in non-volatile memory during conditions where the power is insufficient. In that case a small storage cell, e.g. a capacitor can be used to cover the energy request while the data is backed up.

Further, it is proposed that said sensor unit comprises a wireless transmitter unit for transmitting sensor signals to a receiving unit.

Though the invention is applicable to other types of rollers such as toroidal rollers or conical rollers, it is preferred the sensor roller is a cylindrical roller in view of the wide field of applicability thereof.

A good match between the typical rotation speed of the rollers and the optimum operation speed of the generator can be achieved if the part of the generator assembly comprises a gearbox provided between an input shaft interacting with the cage and a rotor of a generator. The gearbox comprises preferably a planetary gear arranged coaxially to the generator shaft.

Preferably, sensor unit, the part of the generator assembly and eventually the gear box in the bore are encapsulated, preferably using a Polyurethane (PUR) potting compound in order to avoid corrosion by aggressive ingredients of lubricants used for the roller. A further aspect of the invention relates to a bearing assembly including an inner ring, an outer ring, a plurality of rollers including at least one sensor roller as described above and a cage guiding said plurality of rollers, wherein the cage is configured to magnetically interact with the part of the generator assembly of the sensor roller.

According to one aspect of the invention, the cage is provided with a permanent magnet located adjacent to the sensor roller such that an air gap is formed between the permanent magnet and a magnetically interacting portion of the generator assembly.

Preferably, the width of the air gap is 1 mm or less. Larger gaps do not enable a sufficiently strong interaction at a given size and strength of the permanent magnets such that slippage may occur or - if the cage or parts of the cage act as a yoke for the generator - the loss of the magnetic field is too important.

The above description of the invention as well as the appended claims, figures and the following description of preferred embodiments show multiple characterizing features of the invention in specific combinations. The skilled person will easily be able to consider further combinations or sub-combinations of these features in order to adapt the invention as defined in the claims to his or her specific needs.

Brief Description of the Drawings

Fig. 1 is a schematic view of a roller bearing including a sensor roller according to the invention.

Fig. 2 is a schematic sectional view of the sensor roller of the bearing of Fig. 1.

Fig. 3 is a schematic sectional view of the sensor roller of a bearing according to a second embodiment of the invention.

Detailed Description of the Embodiments Fig. 1 is a schematic view of a roller bearing including a sensor roller 10a according to the invention.

The bearing is a single-row roller bearing including one sensor roller 10a communicating in a wireless way with a remote receiver unit 12, which may be fixed e.g. to the stationary ring 14 of the bearing or to a housing or shaft retaining the stationary ring 14. The receiver unit 12 may have integrated data processing means or an interface for forwarding the received data to a further control- and monitoring unit (not shown) which processes the sensor data as desired.

The bearing includes an inner ring 16, an outer ring 14 and a plurality of cylindrical rollers 10 including the sensor roller 10a. In the case of this embodiment, the outer ring 14 is the stationary ring.

The rollers 10 are arranged in a cage 18 between the inner ring 16 and the outer ring 14. At the position of the sensor roller 10a, the cage 18 is provided with a disk-shaped permanent magnet 20 such that the symmetry axis of the disk-shape of the permanent magnet 20 coincides with the rotation axis of the roller in the cage 18. The magnetization direction 22 of the permanent magnet 20 is illustrated with an arrow in Fig. 1 and is perpendicular to the symmetry axis and to the rotation axis. The orientation of the magnetization axis within the plane perpendicular to the symmetry axis and to the rotation axis is chosen to be the circumferential direction of the bearing in this embodiment, but may be chosen otherwise if desired.

Fig. 2 is a schematic sectional view of the sensor roller 10a of the bearing of Fig. 1.

The sensor roller 10a is provided with a bore 24 accommodating a sensor unit 26 and at least a part of a generator assembly 28. The part of the generator assembly 28 integrated in the sensor roller 10a is configured to interact with the cage 18 in order to generate energy out of a relative rotation between the cage 18 and the sensor roller 10a.

The generator assembly 28 includes a generator 30 proper, which is preferably formed as a brushless DC generator, an AC-DC and energy storage circuit 32 and a wireless monitoring node 34. The wireless monitoring node 34 includes the sensor unit 26 and a wireless transmitter unit 36 for transmitting the sensor signals to the receiver unit 12 in a wireless way.

The AC-DC and energy storage circuit 32 comprises a simple rectifier 38 with voltage output regulator (buck/boost) and the energy storage is achieved with a simple capacitor 40, wherein more complicated tasks may require more complicated energy storage solutions.

A generator shaft 42 of the generator 30 is provided with a permanent magnet 44 at its shaft end, wherein said magnet 44 is configured to interact with the magnet 20 provided on the cage 18 described above. The permanent magnet 20 of the cage 18 located adjacent to the sensor roller 10a such that an air gap is formed between the permanent magnet 20 one the cage 18 and the permanent magnet 44 on the shaft hand, the latter being the magnetically interacting portion of the generator assembly 28. The width of the air gap is set to 1 mm or less, e.g. 0.2 mm.

The shapes and magnetization of the two magnets 20, 44 are identical, wherein a relative rotation is possible if a magnetic force generating an angular momentum is overcome. The angular momentum restores the relative orientation of the magnets 20, 44 toward the rest configuration with minimum magnetic field energy, i.e. to the configuration illustrated in Fig. 2 in which the magnetization directions of the two magnets 20, 44 are opposite to one another. The width of the air gap is chosen such that the magnetic interaction or restoration force is sufficiently strong to keep the magnets 20, 44 in the or close to the rest configuration as described above, whereas an overlocking or slipping is possible if angular momenta other than the angular momentum 5 generated by the magnetic interaction acting on the generator shaft 42

exceed the angular momentum generated by the magnetic interaction.

The wireless monitoring node 34 including the sensor unit 26 and the generator assembly 28 in the bore 24 are encapsulated using a PUR potting i o compound in order to avoid corrosion by aggressive ingredients of lubricants used for the roller.

Figure 3 shows a further possible embodiment of the invention. In order to avoid repetitions, the following description focuses on differences to the embodiment of 15 Figure 1 and 2 and the reader is referred to the description of Figures 1 and 2 for features which are similar or identical. In order to highlight the common function or concept, the same or similar reference numbers are employed for features having identical or very similar functions.

20 Fig. 3 is a schematic sectional view of the sensor roller 10a of a bearing according to a second embodiment of the invention. In addition to the components of the generator assembly 28 of Figs 1 and 2, the part of the generator assembly 28 arranged inside of the bore 24 comprises a gearbox 46 provided between an input shaft interacting with the cage 18 and a rotor of a generator 30. The permanent

25 magnet 44 is mounted on the end of a shaft 48 of the gearbox 46.

The gearbox 46 enables an adaptation of the typical rotation speed of the roller to an optimum speed range of the generator in cases where the latter two ranges of rotation speeds differ too much.

30

The invention according to both embodiments allows to dispense with an external power source and the power can be internally generated for the entire lifetime of the bearing. Compared to an embedded eccentric

mass/pendulum type of solution, much more power can be generated due to the fact that the force that can be transmitted via the magnetic interaction between the cage 18 and the generator shaft 42 is rather high compared to the force generated by the eccentric mass.