Mobile Communication

Study on driving force of vibrational friction motor

With mobile communication and computing becoming popular, demands for the miniaturization and higher performance of information equipments are growing. The vibrational friction motor has a high potential as an actuator for micro-sized memories and output devises since it has a simple structure and uses friction force that is a dominant force in micro domain. The prototype motor has been manufactured ⁽¹⁾, but the method of design and estimation has not been established yet because the driving mechanism of the motor is complicated due to the sequence motion of vibration, collision, and friction.

Figure 1 shows the structure of the vibrational friction motor. The stator consists of oscillators with PZT film. Figure 2 shows the process of the driving force being generated. The driving mechanism is such that the stator is excited at the resonant frequency by PZT, and the stator top collides with the rotor obliquely, and the frictional force generates the tangential force to the rotor surface. The driving force of this motor depends on both the vibrational condition of the stator and the contact condition between the stator and the rotor. As the first step, the driving force is estimated qualitatively by analyzing only the vibration of stator by FEM. Next, the instrument to measure colliding force is fabricated and the influence of the coefficient of restitution and the coefficient of friction is clarified experimentally.


Figure 1. Vibrational friction motor


Figure 2. Principle of driving force