Magnetic Flux Distribution in the Air-Gap of Cylindrical- and Disc-Form DC Micromotors used for Mobile Phones

Mobile phones have a vibration function generated by a vibration motor. There are two types of the used vibration motors (DC): the bell-rotor motor and the discrotor motor. Both of them employ a rare-earth magnet to the magnetic excitation of the motor. In both cases the motor construction determines the shape of the air-gap. We have measured the magnetic induction in the air-gap in both vibration motors. A two-dimensional finite-element method (FEM) has been used to calculate extensively the magnetic field of a rare-earth magnet (NdFeB) in the air-gap. The measured and the simulated air-gap induction results are compared in this paper