Ultrasonic transducer having state monitoring function and ultrasonic cleaning device using the same

An ultrasonic cleaning device, comprising:

• a plurality of Langevin ultrasonic transducers configured to apply ultrasonic vibrations to cleaning liquid, the ultrasonic cleaning device configured to clean an object to be cleaned via the cleaning liquid to which the ultrasonic vibrations are applied by the plurality of Langevin ultrasonic transducers;
• and
• a processing section configured to monitor a vibration state of the ultrasonic vibrations applied by the plurality of Langevin ultrasonic transducers, wherein
• the plurality of Langevin ultrasonic transducers include a plurality of state monitoring ultrasonic transducers having a state monitoring function,
• each one of the plurality of state monitoring ultrasonic transducers comprises a plurality of piezoelectric elements, which are arranged to be stacked on each other and are expandable and contractable in a direction of the stacking,
• a part of the plurality of piezoelectric elements serves as a vibration exciting piezoelectric element configured to expand and contract by being applied with an AC voltage,
• another part of the plurality of piezoelectric elements serves as a state monitoring piezoelectric element, which is fixed to the vibration exciting piezoelectric element in a pressurized state, and is configured to output a state monitoring voltage by the expansion and contraction of the vibration exciting piezoelectric element, and
• the processing section is configured to:
• monitor a state of each one of the plurality of Langevin ultrasonic transducers with a change in at least one of an amplitude or a frequency of the state monitoring voltage output from one or more of the state monitoring piezoelectric elements included in one or more of the plurality of state monitoring ultrasonic transducers around each one of the plurality of Langevin ultrasonic transducers;
• and
• estimate a position of one of the plurality of Langevin ultrasonic transducers in an abnormal state from one or more positions of the one or more of the state monitoring piezoelectric elements from which the change is detected.