This work deals with the refinement of the electrical impedance model of rolling bearings, in order to predict bearing forces via the measurement of the impedance. The purpose of this model is to use rolling bearings as a load sensor by measuring the impedance. Therefore, radially loaded deep groove ball bearings under elastohydrodynamic lubrication conditions are investigated in this work. The state of the art describes rolling contacts as plate capacitors whose plate spacing is the lubricant film thickness and whose area is the Hertzian area. In addition, the influence of the non-deformed area around the Hertzian area is described with a factor that depends on the lubricant film thickness and the radial load. In recent research about the individual contact, the influence of this non-deformed region has been described phenomenologically by a calculation of the electric field, replacing the empirical factor. An important contradiction can be derived from literature: unloaded rolling elements, having no Hertzian area, have no capacitance, but at the same time non-deformed areas outside the Hertzian area provide a contribution to the capacity of loaded rolling elements. In addition, the capacitance of unloaded rolling elements has already been proven by measurement. For this reason, the impedance model of rolling bearings is extended in this work to take the influence of unloaded rolling elements, and the phenomenological model of the non-deformed area from the research on the single contact into account. The calculated rolling bearing impedance of this extended model is compared with test data and it is shown that the extended model is an improvement compared to the state of the art. In addition to the impedance value, the frequency spectrum of the measurement is also investigated and a model is developed to describe the frequencies that occur. This model is based on the assumption that the occurring frequencies essentially depend on unbalance forces and the number of rolling elements in the load zone. If the radial load vector points to one rolling element or exactly between two rolling elements, two dif-ferent electrical impedance values result. The regular change of the impedance between these states is visible as a peak in the frequency spectrum. After validation of the developed model, the amplitudes of these frequencies are used to compare the extension of the impedance model with the state of the art. It is shown that the model extension describes the measured rolling bearing impedance with a significantly lower, almost con-stant difference. Finally, approaches are shown to generalize and transfer the extended model to various rolling bearing types. | English |