A Study of Hall Element Method for Ball Motion in a Ball Bearing

Determining the actual ball motion in a ball bearing is important for tribological analysis, such as estimating oil film thickness, heat generation, etc. Generally, the method used for this purpose is to measure the magnetic field change induced by the rotation of a magnetized ball. In earlier studies, a search coil was used to detect the ball motion, by means of which three-dimensional ball motion was not available. Recently, Kawakita developed the Hall element method, in which Hall elements were arranged so as to detect three-dimensional ball motion. In his method, in spite of the fact that the radial direction components of the magnetic flux were measured through contact points, a fixed cartesian coordinate system was used regardless of the contact condition. In this study, the direction of the contact points was taken into consideration to calculate the Hall voltage and to estimate the angular velocity error due to a fixed cartesian coordinate system. The resultsshow that the direction of the contact points considerably affects the angular velocity calculation.