A rotation shaft support structure of a motor includes a shaft tube having an inner wall provided with at least one bearing. The ultrasonic applicator comprises an ultrasonic transducer having an acoustic window, and an ultrasonic vibratory element, the ultrasonic vibratory element having a convergent shape with a focus located in the direction of the acoustic window. Periodically, as defined by the pre-defined period, the then-current referenced rate is compared to a base referenced rate that was defined at the establishment of the guarantee period.