Development of a vibration motor with open delta windings used for mobile telecommunication devices

With the remarkable expansion of communication industry, a cellular phone has become a necessary communication device in modern society. However, a paging signal by a buzzer often acts as an unpleasant noise in some places, thus necessitating a paging signal by a vibration motor. The conventional flat type vibration motor uses three-phase windings with three phase coils. In this paper, the authors present a new design of vibration motor which uses an open delta winding with two phase coils. The proposed two-phase motor design enables removal of dead points, simpler configuration and thus higher productivity. For an electromagnetic field analysis, it is possible to reduce the 3D problem to a 2D boundary-value problem. Due to the motor symmetry, 2D modeling can be implemented for fast computation and the output torque is calculated by FEM. With the comparison of output torque, it is possible to evaluate the performance and characteristics of vibration motors. Experimental results on vibration measurements are also followed to confirm the validity of the proposed design.