Piezoelectric adjusting element

A piezoelectric adjusting element in the form of a monolithic plate-shaped or cylindrical piezoelectric oscillator, the piezoelectric oscillator having first and second main surfaces and groups of electrodes allocated to the first and second main surfaces, the piezoelectric adjusting element comprising:

• a housing;
• a driven element;
• at least one friction layer arranged on at least the housing or on the driven element;
• an electric excitation source connected to the groups of electrodes of the piezoelectric oscillator, the piezoelectric oscillator being in friction contact with the friction layer;
• and wherein
• the piezoelectric oscillator is excited by the groups of electrodes to generate standing longitudinal acoustic waves in directions of oscillator resonant length and oscillator resonant height, respectively of the piezoelectric oscillator, the oscillator resonant length being an integral multiple of wave length of the standing longitudinal wave vibrating in the direction of oscillator resonant length, and the oscillator resonant height is equal to one half of wave length of the standing longitudinal wave vibrating in the direction of the oscillator resonant height, and the oscillator resonant length and the oscillator resonant height are chosen such that the frequencies of the standing longitudinal acoustic waves expanding by the piezoelectric oscillator are equal both in the direction of the oscillator resonant length as well as in the direction of the oscillator resonant height.