Kiyokazu Asai

Piezoelectrically driven ultrasonic transducer

An ultrasonic transducer comprising a first cylindrical member which includes a mechanical vibration amplifying part formed in symmetry around the axis thereof and having a gradually increased cross-sectional area toward a base portion thereof, the base portion having a flat surface perpendicular to the axis thereof, and an annular rigid part formed with the mechanical vibration amplifying part coaxially therewith, the annular rigid part being extended from the outer wall of the base portion axially and radially outwardly to have sufficient rigidity and weight, and the annular rigid part being provided, in the proximity of the outer wall of the base portion, with an annular groove or gap having a predetermined axial depth in order to reduce the diameter of the flat surface. The transducer further comprises a second cylindrical member which includes a backing block of a cylindrical body, a base portion of which is formed with a flange and a flat surface perpendicular to the axis thereof having the larger diameter than that of the flat surface of the first cylindrical member. An ultrasonic transducer portion is interposed between the flat surfaces of the first and second cylindrical members and comprises a pair of piezoelectric elements having flat surfaces perpendicular to the axis of the first and second surfaces, and an electrode plate interposed between the pair of piezoelectric elements. A fastening device pressingly abuts the flat surfaces of the piezoelectric elements against the flat surfaces of first and second cylindrical members and integrally clamps the annular rigid part and the flange of the second cylindrical member to each other in a manner to circumvent said annular groove or gap. The ultrasonic transducer prevents the flexural vibration of the flat surface of the first cylindrical member and prevents cracking of piezoelectric elements to ensure stabilized operations without transitional variations in electric impedance and resonance frequency and to allow continuous vibrating operations in large amplitude over a long period of time.

High Power Travelling-Wave Type Ultrasonic Motor

We have performed an experiment aimed at developing a high power ultrasonic motor based on a thin, lightweight, travelling-wave type design. This paper presents a detailed analysis of experimental results. Three prototype motors of the improved type were fabricated, having outer diameters of 50, 70 and 90 mm. Compared to a motor employing a piezoelectric element of the same outer diameter and the same resistive resin material as conventional types of motors, approximately twice as high maximum torque and four times as high maximum output power have been obtained with the prototype motors. It has also been confirmed that these motors have sufficient durability to withstand high-loads.

A New Hollow Cylindrical Ultrasonic Wave Radiator

The design and performance of a new hollow cylindrical ultrasonic wave radiator which has a large vibratory surface are presented. The vibrating system is composed of a hollow cylinder connected to an ultrasonic horn that serves simultaneously as a mechanical resonant transmitter. The hollow cylindrical vibrator has a flexural vibration in a radial direction on all its extensive surface areas. Liquid supplied to the nodal lines of the flexural vibration is atomized on the outer or inner circumferential surface of the vibrating cylinder. A stable atomization of a large amount of liquid per unit time can be achieved.