LOAD MEASUREMENT DEVICE AND METHOD FOR DETERMINING LOAD Background of the Invention

It is known to measure a load acting on a deformable component using a piezo sensor attached to a first portion of the component. A deformation of the component induces stress in the piezo element and the stress leads to a detectable voltage. The transfer of stress requires at least two attachment points of the piezo sensor and the inevitable mechanical contact is susceptible to damages and may influence the results of the measurement.

Highly miniaturized 3D acceleration sensors are known from the field of tele- communication. State-of-the art 3D-acceleration sensors may have an angular resolution of 0,1 degrees or below.

US2012/0210791 A1 discloses a torque measuring device with acceleration sensors attached to the ends of a torque bar, respectively. A further torque measuring device using acceleration sensors is disclosed in US2013/030842A2.

Summary of the Invention

The invention seeks to provide an alternative load measurement device requiring only one point of contact to a deformable component.

The invention relates to a load measuring device including a deformable component configured to be deformed under a load to be measured and a sensor assembly to a first portion of said deformable component.

It is proposed that the sensor assembly includes at least one acceleration sensor configured to detect a change in an orientation of said first portion with regard to the direction of gravity. The deformable component is a seal to be in sliding contact with a component configured to rotate in relation to the seal. In a preferred embodiment of the invention, said acceleration sensor is formed as a semiconductor based 3-axis acceleration sensor.

In applications where an apparatus including the deformable component may change its orientation with regard to the gravity direction as a whole, it may be necessary to calibrate the sensor signals. In this case, the sensor assembly preferably includes at least two acceleration sensors attached to different portions of said component. A data processing device configured to evaluate the sensor signals and to calculate the load based thereon may determine the difference between the orientations of the acceleration sensors in order to discount a rotation or displacement of the deformable component.

According the invention, the deformable component is formed as a bearing seal. It has turned out that in particular in the case of large-size bearings, the orientation of certain portions of a sealing lip may change in response to radial or axial loads acting on the bearing in an amount sufficient to be detected.

In preferred embodiments of the invention, the load measuring device includes a data processing device configured to calculate a load acting on the deformable component based on the signals obtained from the sensor assembly. The data processing device may use e.g a characteristic determined using test loads and stored in a memory device.

A further aspect of the invention prelates to a method for determining a load acting on a deformable component using a load measurement device as described above. In the method according to the invention, the load is determined using signals of an acceleration sensor, wherein said acceleration sensor is attached to a first portion of said component in order to detect a change in an orientation of said first portion with regard to the direction of gravity.

In the context of the invention, the expression load is to be construed broadly as covering static load, dynamic load, linear load, shear load or torque load in the context of the invention. The above embodiments of the invention as well as the appended claims and figures show multiple characterizing features of the invention in specific combina- tions. 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 specific needs. Brief Description of the Figures

Fig. 1 is a schematic illustration of a load measurement device related to the invention;

Fig. 2 is a schematic illustration of a load measurement device related to the invention including a torque bar; and

Fig. 3 is a schematic illustration of a bearing equipped with a load measurement device according to a third embodiment of the invention.

Detailed Description of the Embodiments

Fig. 1 is a schematic illustration of a load measurement device related to the invention.

The load measuring device according to Fig, 1 includes a deformable compo- nent 10 formed as a bar configured to be deformed under a load L to be measured. The bar 10 is fixed to a support 17 on one of its ends, is oriented horizontally, i.e. perpendicular to the direction of gravity G, and is configured to support the load L on the other one of its ends. A sensor assembly 12 including an acceleration sensor 14, more specifically a 3- axis acceleration sensor, is attached to a first portion close to a free end of the deformable component 10. The gyro sensor 14 is configured to detect a change in an orientation of said first portion with regard to the direction of gravity G. In applications where an apparatus including the deformable component 10 may change its orientation with regard to the gravity direction G as a whole, such as in vehicles running up and down slopes, it may be necessary to calibrate the sensor signals. In this case, the sensor assembly 12 may be provided with at least two acceleration sensors 14a, 14b attached to different portions of said component. A data processing device 16 configured to evaluate the sensor signals and to calculate the load based thereon may determine the difference between the orientations of the acceleration sensors 14 in order to discount a rotation or displacement of the deformable component 10.

Fig. 2 illustrates a related device where the deformable component 10 is a torque bar. Two acceleration sensors 14a, 14b are attached to opposite ends of the torque bar 10 and measure a difference in the relative orientation of the accelera- tion sensors 14 as a consequence of a twisting of the torque bar 10.

Fig. 3 illustrates third embodiment of the invention wherein the deformable component 10 is formed as a bearing seal, preferably attached to an outer ring of a bearing. The seal 10 has a profile with an inclined portion 10c connecting a fixing portion 10a of the seal supported by a metallic flange with a contact portion 10b of the seal 10, wherein the contact portion 10b is in sliding contact with an inner ring 20 of the bearing. In further embodiments of the invention, the seal 10 might be in sliding contact with a rotating shaft 20 or the seal 10 might be attached to an inner ring of the bearing.

High radial loads acting on the bearing may lead to a deformation of the bearing rings and/or to a redistribution of the roller elements of the bearing such that the radial distance between the rings of the bearing in the main load direction depends on the radial load. The orientation of the inclined portion 10c of the sealing lip in space will therefore change in response to radial or axial loads acting on the bearing in an amount sufficient to be detected.

Though only illustrated in the embodiment of Fig. 3, the load measuring device may include a data processing device 16 configured to calculate a load acting on the deformable component 10 based on the signals obtained from the sensor assembly 12. The data processing device 16 may use e.g. a characteristic determined using test loads and stored in a memory device.

The above embodiment of the invention relates to a method for determining a load acting on a deformable component 10 using a load measurement device as described above. In the method according to the invention, the load is determined using signals of one acceleration sensor 14 or multiple acceleration sensors 14, wherein said at least one acceleration sensor 14 is attached to a first portion of said component in order to detect a change in an orientation of said first portion with regard to the direction of gravity G.