Nihon Kikai Gakkai ronbunshu (Oct 2019)

An experimental attempt at measurement of bearing load in deep groove ball bearing with eddy current method

  • Akitoshi TAKEUCHI

DOI
https://doi.org/10.1299/transjsme.19-00273
Journal volume & issue
Vol. 85, no. 878
pp. 19-00273 – 19-00273

Abstract

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Eddy current method which is uninfluenced by oil film rupture or viscosity change was employed as a simple in-situ estimation method of bearing load acting on deep groove ball bearing operating under low rotational speed. The estimation of the bearing load was performed through the observation of output voltage change of eddy current flaw detector. The output voltage is influenced with the inductance change of the coil in probe that is decided by the mean gap between ball and outer ring which has weak leakage magnetic flux. Since the mean gap is determined with the elastic deformation of contact point due to the bearing load, then measurement of the bearing load becomes possible with the observation of output voltage. The excitation frequency which shows the maximum sensitivity for the change of mean gap is determined by the balance of the increasing effect of eddy current intensity according to the increase of excitation frequency and of the skin effect decreasing the penetration depth of eddy current in high frequency region. Since the leakage magnetic flux region on the rear surface of outer ring in high excitation frequency case becomes narrow due to the skin effect, the evaluation of mean gap using high frequency is carried out within the thin gap region in the vicinity of contact point of ball and outer ring, compared to low excitation frequency case having thicker mean gap due to the wide leakage magnetic flux region. Then, the output voltage change for the bearing load becomes large and measurement sensitivity is improved. As mentioned above, the basic characteristics of eddy current method for the measurement of bearing load were examined, and the potential of this technique as the simple bearing load measurement method was cleared experimentally.

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