Ultrasonic wave generator

• US 3,967,143 A
• Filed: 10/10/1974
• Issued: 06/29/1976
• Est. Priority Date: 10/10/1974
• Status: Expired due to Term

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Watanabe, Akinori, Ando, Takao, Tanoshima, Katsuhide, Nagano, Akio, Tohama, Akira
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US05/513,752
• Time in Patent Office: 628 Days
• Field of Search: 310/8.1, 331/116 R, 318/116, 318/118
• US Class Current: 310/316.01
• CPC Class Codes: B06B 1/0261 taken from a transducer or electrode connected to the driving transducer
• CPC Class Codes: B06B 1/0276 with simultaneous generation, e.g. with modulation, harmonics
• CPC Class Codes: B06B 2201/55 Piezoelectric transducer

Abstract

The ultrasonic wave generator of the present invention always drives a transducer with the resonant frequency f_o of the transducer. Although the resonant frequency f_o changes due to the temperature change etc., the driving frequency automatically follows the change of the resonant frequency f_o. The control of the driving frequency is performed by means of a feed-back loop including a voltage controlled oscillator and means for applying a control signal to said voltage controlled oscillator according to the amplitude and/or phase of the driving signal of the transducer.

Claims

1. An ultrasonic wave generator comprising at least a transducer for generating an ultrasonic wave having at least a driving electrode and a detection electrode, a variable frequency oscillator whose output signal is applied to said driving electrode, and a slope detection circuit which detects the amplitude of the output signal of said detection electrode and controls the output frequency of said variable frequency oscillator for obtaining the maximum amplitude of output signal in said detection electrode.

2. An ultrasonic wave generator according to claim 1, further comprising a binary counter connected between said slope detection circuit and said variable frequency oscillator, the status of said binary counter being changed when the output amplitude of said detection electrode is reduced, and said binary counter controlling the output frequency of said variable frequency oscillator through an integral circuit.

3. An ultrasonic wave generator according to claim 2, further comprising an oscillator whose output is connected to the input of said binary counter through an OR circuit.

4. An ultrasonic wave generator comprising at least a transducer for generating an ultrasonic wave;

a voltage controlled oscillator whose output is connected to said transducer through an amplifier;

a detection means having a series circuit of a current detector for detecting the driving current of said transducer, a rectifier for adjusting the output signal of said current detector and a band pass filter connected to the output of said rectifier;

an analog adder whose output is connected to the input of said voltage controlled oscillator;

a modulation wave oscillator connected to one input of said analog adder;

a phase selection circuit which picks up the output of said detection means according to the output amplitude of said modulated wave oscillator; and

a low pass filter, the input of which is connected to the output of said phase selection circuit, the output of said low pass filter being connected to the other input of said analog adder.